[PATCH v2 1/2] iio: document ti-dac8554 devicetree bindings

[PATCH v2 1/2] iio: document ti-dac8554 devicetree bindings

[Nikolaus Schulz]

Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
---
 .../devicetree/bindings/iio/dac/ti-dac8554.txt     | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt

diff --git a/Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt b/Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt
new file mode 100644
index 0000000..16f7178
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt
@@ -0,0 +1,22 @@
+TI DAC8554 Digital to Analog Converter
+
+This driver supports the SPI bus.
+
+Required properties:
+	- compatible: must be "ti,dac8554"
+	- vref-supply: the vref power supply
+	- address: the additional 2-bit chip address
+
+For required properties on SPI, please consult
+Documentation/devicetree/bindings/spi/spi-bus.txt
+
+Example:
+
+	dac8554@0 {
+		compatible = "ti,dac8554";
+		reg = <0>;
+		spi-max-frequency = <50000000>;
+
+		vref-supply = <&vdd_vref>;
+		address = <0>;
+	};
-- 
2.1.3

[PATCH v2 2/2] iio: add driver for the TI DAC8554

[Nikolaus Schulz]

The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
interface.

Changes in v2:
* Use DMA-safe buffer for SPI transfer
* Normalize powerdown_mode name "hi-z" to "three_state" as per
  ABI/testing/sysfs-bus-iio
* Register device late in probe function
* Avoid powerdown broadcast update, which touches all DAC on the bus

Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
---
 drivers/iio/dac/Kconfig      |  10 ++
 drivers/iio/dac/Makefile     |   1 +
 drivers/iio/dac/ti-dac8554.c | 374 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 385 insertions(+)
 create mode 100644 drivers/iio/dac/ti-dac8554.c

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 2236ea2..1689260 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -181,4 +181,14 @@ config MCP4922
 	  To compile this driver as a module, choose M here: the module
 	  will be called mcp4922.
 
+config TI_DAC8554
+	tristate "TI DAC8554 driver"
+	depends on SPI
+	depends on OF
+	help
+	  Say yes here to build the driver for the TI DAC8554.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called ti-dac8554.
+
 endmenu
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 52be7e1..b98d79a 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -20,3 +20,4 @@ obj-$(CONFIG_MAX517) += max517.o
 obj-$(CONFIG_MAX5821) += max5821.o
 obj-$(CONFIG_MCP4725) += mcp4725.o
 obj-$(CONFIG_MCP4922) += mcp4922.o
+obj-$(CONFIG_TI_DAC8554) += ti-dac8554.o
diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
new file mode 100644
index 0000000..fca751f
--- /dev/null
+++ b/drivers/iio/dac/ti-dac8554.c
@@ -0,0 +1,374 @@
+/*
+ * TI DAC8554 Digital to Analog Converter SPI driver
+ *
+ * Copyright (C) 2014 Avionic Design GmbH
+ *
+ * Based on ad5446r_spi.c
+ * Copyright (C) 2010,2011 Analog Devices Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/spi/spi.h>
+#include <linux/regulator/consumer.h>
+#include <linux/module.h>
+#include <linux/iio/iio.h>
+#include <linux/of.h>
+
+#define DAC8554_DRIVERNAME			"ti-dac8554"
+#define DAC8554_DAC_CHANNELS			4
+
+/* Load commands */
+#define DAC8554_CMD_STORE_DAC_N			0x0
+#define DAC8554_CMD_UPDATE_DAC_N		0x1
+#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
+#define DAC8554_CMD_UPDATE_BROADCAST		0x3
+
+#define DAC8554_BROADCAST_USE_SRDATA		0x2
+/* Powerdown modes (ORed PD1|PD2 bits) */
+#define DAC8554_PWRDN_HIZ			0x0
+#define DAC8554_PWRDN_1K			0x1
+#define DAC8554_PWRDN_100K			0x2
+
+#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
+
+/**
+ * struct dac8554_state - driver instance specific data
+ * @spi:		spi_device
+ * @reg:		supply regulator
+ * @addr:		two-bit chip address
+ * @vref_mv:		reference voltage in millivolt
+ * @val			DAC/channel data
+ * @powerdown		channel powerdown flag
+ * @powerdown_mode	channel powerdown mode
+ * @xfer		SPI transfer buffer
+ */
+struct dac8554_state {
+	struct spi_device		*spi;
+	struct regulator		*reg;
+	unsigned			addr;
+	unsigned			vref_mv;
+	u16				val[DAC8554_DAC_CHANNELS];
+	bool				powerdown[DAC8554_DAC_CHANNELS];
+	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
+
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	u8				xfer[3] ____cacheline_aligned;
+};
+
+static int dac8554_spi_write(struct dac8554_state *st,
+			     unsigned cmd,
+			     unsigned chan_addr,
+			     unsigned val)
+{
+	u32 data;
+
+	/*
+	 * The input shift register is 24 bits wide. The 8 MSB are
+	 * control bits, followed by 16 data bits.
+	 * The first two bits A1 and A0 address a DAC8554 chip.
+	 * The next two are the command bits, LD1 and LD0.
+	 * After a don't-care-bit, the next two bits select the channel.
+	 * The final control bit PD0 is a flag signalling if the data
+	 * bits encode a powerdown mode. We merge PD0 with the adjacent
+	 * data bits.
+	 */
+
+	if (cmd > 3 || chan_addr > 3 ||
+			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
+		return -EINVAL;
+
+	data = (st->addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
+	st->xfer[0] = data >> 16;
+	st->xfer[1] = data >> 8;
+	st->xfer[2] = data;
+
+	return spi_write(st->spi, st->xfer, sizeof(st->xfer));
+}
+
+static int dac8554_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val,
+			    int *val2,
+			    long m)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	switch (m) {
+	case IIO_CHAN_INFO_RAW:
+		*val = st->val[chan->address];
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = st->vref_mv;
+		*val2 = 16;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	}
+	return -EINVAL;
+}
+
+static int dac8554_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val,
+			     int val2,
+			     long mask)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+	int err;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (val > 0xffff || val < 0)
+			return -EINVAL;
+
+		err = dac8554_spi_write(st, DAC8554_CMD_UPDATE_DAC_N,
+					chan->address, val);
+		if (err)
+			return err;
+
+		st->val[chan->address] = val;
+
+		/* By hw design, DAC updates automatically trigger powerup. */
+		st->powerdown[chan->address] = false;
+
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	return st->powerdown_mode[chan->address];
+}
+
+static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan,
+				      unsigned int mode)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	st->powerdown_mode[chan->address] = mode;
+
+	return 0;
+}
+
+static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
+					  uintptr_t private,
+					  const struct iio_chan_spec *chan,
+					  char *buf)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
+}
+
+static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
+					   uintptr_t private,
+					   const struct iio_chan_spec *chan,
+					   const char *buf,
+					   size_t len)
+{
+	bool powerdown;
+	int ret;
+	struct dac8554_state *st = iio_priv(indio_dev);
+	u8 powerdown_mode;
+
+	ret = strtobool(buf, &powerdown);
+	if (ret)
+		return ret;
+
+	st->powerdown[chan->address] = powerdown;
+
+	if (powerdown) {
+		powerdown_mode = st->powerdown_mode[chan->address];
+		ret = dac8554_spi_write(st,
+				DAC8554_CMD_UPDATE_DAC_N,
+				chan->address,
+				DAC8554_PWRDN_TO_SR(powerdown_mode));
+	} else {
+		/* Load DAC with cached value. This triggers a powerup. */
+		ret = dac8554_spi_write(st,
+				DAC8554_CMD_UPDATE_DAC_N,
+				chan->address,
+				st->val[chan->address]);
+	}
+
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static int dac8554_powerdown(struct dac8554_state *st,
+			     u8 powerdown_mode)
+{
+	int chan, cmd, ret;
+
+	for (chan = DAC8554_DAC_CHANNELS-1; chan >= 0; --chan) {
+		cmd = chan ? DAC8554_CMD_STORE_DAC_N
+			   : DAC8554_CMD_STORE_DAC_N_UPDATE_ALL;
+		ret = dac8554_spi_write(st, cmd, chan,
+				DAC8554_PWRDN_TO_SR(powerdown_mode));
+		if (ret)
+			return ret;
+	}
+
+	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
+	memset(st->powerdown, true, sizeof(st->powerdown));
+
+	return 0;
+}
+
+static const struct iio_info dac8554_info = {
+	.write_raw = dac8554_write_raw,
+	.read_raw = dac8554_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static const char * const dac8554_powerdown_modes[] = {
+	"three_state",
+	"1kohm_to_gnd",
+	"100kohm_to_gnd"
+};
+
+static const struct iio_enum dac8854_powerdown_mode_enum = {
+	.items = dac8554_powerdown_modes,
+	.num_items = ARRAY_SIZE(dac8554_powerdown_modes),
+	.get = dac8554_get_powerdown_mode,
+	.set = dac8554_set_powerdown_mode,
+};
+
+static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
+	{
+		.name = "powerdown",
+		.read = dac8554_read_dac_powerdown,
+		.write = dac8554_write_dac_powerdown,
+		.shared = IIO_SEPARATE,
+	},
+	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
+		 &dac8854_powerdown_mode_enum),
+	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
+	{ },
+};
+
+#define DAC8554_CHANNEL(chan) { \
+	.type = IIO_VOLTAGE, \
+	.indexed = 1, \
+	.output = 1, \
+	.channel = (chan), \
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+	.address = (chan), \
+	.ext_info = dac8554_ext_info, \
+}
+const struct iio_chan_spec dac8554_channels[] = {
+	DAC8554_CHANNEL(0),
+	DAC8554_CHANNEL(1),
+	DAC8554_CHANNEL(2),
+	DAC8554_CHANNEL(3),
+};
+#undef DAC8554_CHANNEL
+
+static int dac8554_probe(struct spi_device *spi)
+{
+	struct dac8554_state *st;
+	struct iio_dev *indio_dev;
+	int ret, voltage_uv;
+	u32 addr;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->name = DAC8554_DRIVERNAME;
+	indio_dev->info = &dac8554_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = dac8554_channels;
+	indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
+
+	spi_set_drvdata(spi, indio_dev);
+
+	st = iio_priv(indio_dev);
+
+	if (!spi->dev.of_node) {
+		dev_err(&spi->dev, "missing OF node");
+		return -ENODEV;
+	}
+	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
+	if (ret || addr < 0 || addr > 2) {
+		dev_err(&spi->dev, "no or invalid chip address");
+		return -ENODEV;
+	}
+
+	st->spi = spi;
+	st->addr = addr;
+
+	st->reg = devm_regulator_get(&spi->dev, "vref");
+	if (IS_ERR(st->reg))
+		return PTR_ERR(st->reg);
+
+	ret = regulator_enable(st->reg);
+	if (ret)
+		return ret;
+
+	voltage_uv = regulator_get_voltage(st->reg);
+	if (voltage_uv < 0)
+		goto error_disable_reg;
+	st->vref_mv = voltage_uv / 1000;
+
+	ret = dac8554_powerdown(st, DAC8554_PWRDN_100K);
+	if (ret)
+		goto error_disable_reg;
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto error_disable_reg;
+
+	return 0;
+
+error_disable_reg:
+	regulator_disable(st->reg);
+	return ret;
+}
+
+static int dac8554_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	regulator_disable(st->reg);
+
+	return 0;
+}
+
+static const struct of_device_id dac8554_of_match[] = {
+	{ .compatible = "ti,dac8554" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dac8554_of_match);
+
+static struct spi_driver dac8554_driver = {
+	.driver = {
+		.name = DAC8554_DRIVERNAME,
+		.owner = THIS_MODULE,
+		.of_match_table = dac8554_of_match,
+	 },
+	.probe = dac8554_probe,
+	.remove = dac8554_remove,
+};
+module_spi_driver(dac8554_driver);
+
+MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz@avionic-design.de>");
+MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
+MODULE_LICENSE("GPL v2");
-- 
2.1.3

Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Hartmut Knaack]

Nikolaus Schulz schrieb am 24.11.2014 um 20:50:
> The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
> interface.
> 
> Changes in v2:
> * Use DMA-safe buffer for SPI transfer
> * Normalize powerdown_mode name "hi-z" to "three_state" as per
>   ABI/testing/sysfs-bus-iio
> * Register device late in probe function
> * Avoid powerdown broadcast update, which touches all DAC on the bus
There are a few issues left, please see my comments inline.
> 
> Signed-off-by: Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
> ---
>  drivers/iio/dac/Kconfig      |  10 ++
>  drivers/iio/dac/Makefile     |   1 +
>  drivers/iio/dac/ti-dac8554.c | 374 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 385 insertions(+)
>  create mode 100644 drivers/iio/dac/ti-dac8554.c
> 
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index 2236ea2..1689260 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -181,4 +181,14 @@ config MCP4922
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called mcp4922.
>  
> +config TI_DAC8554
> +	tristate "TI DAC8554 driver"
> +	depends on SPI
> +	depends on OF
> +	help
> +	  Say yes here to build the driver for the TI DAC8554.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called ti-dac8554.
> +
>  endmenu
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index 52be7e1..b98d79a 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -20,3 +20,4 @@ obj-$(CONFIG_MAX517) += max517.o
>  obj-$(CONFIG_MAX5821) += max5821.o
>  obj-$(CONFIG_MCP4725) += mcp4725.o
>  obj-$(CONFIG_MCP4922) += mcp4922.o
> +obj-$(CONFIG_TI_DAC8554) += ti-dac8554.o
> diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
> new file mode 100644
> index 0000000..fca751f
> --- /dev/null
> +++ b/drivers/iio/dac/ti-dac8554.c
> @@ -0,0 +1,374 @@
> +/*
> + * TI DAC8554 Digital to Analog Converter SPI driver
> + *
> + * Copyright (C) 2014 Avionic Design GmbH
> + *
> + * Based on ad5446r_spi.c
> + * Copyright (C) 2010,2011 Analog Devices Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/spi/spi.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/module.h>
> +#include <linux/iio/iio.h>
> +#include <linux/of.h>
> +
> +#define DAC8554_DRIVERNAME			"ti-dac8554"
> +#define DAC8554_DAC_CHANNELS			4
> +
> +/* Load commands */
> +#define DAC8554_CMD_STORE_DAC_N			0x0
> +#define DAC8554_CMD_UPDATE_DAC_N		0x1
> +#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
> +#define DAC8554_CMD_UPDATE_BROADCAST		0x3
> +
> +#define DAC8554_BROADCAST_USE_SRDATA		0x2
Add a blank line here.
> +/* Powerdown modes (ORed PD1|PD2 bits) */
It took my some time to figure out ORed. I think you could drop it and just
mention (PD1 | PD2 bits).
> +#define DAC8554_PWRDN_HIZ			0x0
> +#define DAC8554_PWRDN_1K			0x1
> +#define DAC8554_PWRDN_100K			0x2
> +
> +#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
> +
> +/**
> + * struct dac8554_state - driver instance specific data
> + * @spi:		spi_device
SPI device?
> + * @reg:		supply regulator
> + * @addr:		two-bit chip address
> + * @vref_mv:		reference voltage in millivolt
> + * @val			DAC/channel data
DAC channel data?
> + * @powerdown		channel powerdown flag
> + * @powerdown_mode	channel powerdown mode
> + * @xfer		SPI transfer buffer
Half of the comments are with colon, the other half are missing it.
> + */
> +struct dac8554_state {
> +	struct spi_device		*spi;
> +	struct regulator		*reg;
> +	unsigned			addr;
> +	unsigned			vref_mv;
> +	u16				val[DAC8554_DAC_CHANNELS];
> +	bool				powerdown[DAC8554_DAC_CHANNELS];
> +	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
> +
> +	/*
> +	 * DMA (thus cache coherency maintenance) requires the
> +	 * transfer buffers to live in their own cache lines.
> +	 */
> +	u8				xfer[3] ____cacheline_aligned;
> +};
> +
> +static int dac8554_spi_write(struct dac8554_state *st,
> +			     unsigned cmd,
> +			     unsigned chan_addr,
> +			     unsigned val)
> +{
> +	u32 data;
> +
> +	/*
> +	 * The input shift register is 24 bits wide. The 8 MSB are
> +	 * control bits, followed by 16 data bits.
> +	 * The first two bits A1 and A0 address a DAC8554 chip.
> +	 * The next two are the command bits, LD1 and LD0.
> +	 * After a don't-care-bit, the next two bits select the channel.
> +	 * The final control bit PD0 is a flag signalling if the data
> +	 * bits encode a powerdown mode. We merge PD0 with the adjacent
> +	 * data bits.
> +	 */
> +
> +	if (cmd > 3 || chan_addr > 3 ||
> +			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
> +		return -EINVAL;
> +
> +	data = (st->addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
Could be more readable by using definition for the magic shifts, or macros.
> +	st->xfer[0] = data >> 16;
> +	st->xfer[1] = data >> 8;
> +	st->xfer[2] = data;
> +
> +	return spi_write(st->spi, st->xfer, sizeof(st->xfer));
> +}
> +
> +static int dac8554_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val,
> +			    int *val2,
> +			    long m)
Commonly, m is called mask (like you do in _write_raw).
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	switch (m) {
> +	case IIO_CHAN_INFO_RAW:
> +		*val = st->val[chan->address];
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = st->vref_mv;
> +		*val2 = 16;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	}
> +	return -EINVAL;
> +}
> +
> +static int dac8554_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int val,
> +			     int val2,
> +			     long mask)
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +	int err;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (val > 0xffff || val < 0)
> +			return -EINVAL;
> +
> +		err = dac8554_spi_write(st, DAC8554_CMD_UPDATE_DAC_N,
> +					chan->address, val);
> +		if (err)
> +			return err;
> +
> +		st->val[chan->address] = val;
> +
> +		/* By hw design, DAC updates automatically trigger powerup. */
> +		st->powerdown[chan->address] = false;
> +
> +		return 0;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
> +				      const struct iio_chan_spec *chan)
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	return st->powerdown_mode[chan->address];
> +}
> +
> +static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
> +				      const struct iio_chan_spec *chan,
> +				      unsigned int mode)
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	st->powerdown_mode[chan->address] = mode;
> +
> +	return 0;
> +}
> +
> +static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
> +					  uintptr_t private,
> +					  const struct iio_chan_spec *chan,
> +					  char *buf)
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
> +}
> +
> +static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
> +					   uintptr_t private,
> +					   const struct iio_chan_spec *chan,
> +					   const char *buf,
> +					   size_t len)
> +{
> +	bool powerdown;
> +	int ret;
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +	u8 powerdown_mode;
> +
> +	ret = strtobool(buf, &powerdown);
> +	if (ret)
> +		return ret;
> +
> +	st->powerdown[chan->address] = powerdown;
> +
> +	if (powerdown) {
> +		powerdown_mode = st->powerdown_mode[chan->address];
> +		ret = dac8554_spi_write(st,
> +				DAC8554_CMD_UPDATE_DAC_N,
> +				chan->address,
> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
The parameters sill fit on line even with proper indentation.
> +	} else {
> +		/* Load DAC with cached value. This triggers a powerup. */
> +		ret = dac8554_spi_write(st,
> +				DAC8554_CMD_UPDATE_DAC_N,
> +				chan->address,
> +				st->val[chan->address]);
Same here with indentation.
> +	}
> +
> +	if (ret)
> +		return ret;
> +
> +	return len;
Just: return (ret) ? ret : len;
> +}
> +
> +static int dac8554_powerdown(struct dac8554_state *st,
> +			     u8 powerdown_mode)
> +{
> +	int chan, cmd, ret;
> +
> +	for (chan = DAC8554_DAC_CHANNELS-1; chan >= 0; --chan) {
Please mind spaces around operators.
> +		cmd = chan ? DAC8554_CMD_STORE_DAC_N
> +			   : DAC8554_CMD_STORE_DAC_N_UPDATE_ALL;
> +		ret = dac8554_spi_write(st, cmd, chan,
> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
> +		if (ret)
> +			return ret;
> +	}
> +
> +	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
> +	memset(st->powerdown, true, sizeof(st->powerdown));
> +
> +	return 0;
> +}
> +
> +static const struct iio_info dac8554_info = {
> +	.write_raw = dac8554_write_raw,
> +	.read_raw = dac8554_read_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static const char * const dac8554_powerdown_modes[] = {
> +	"three_state",
> +	"1kohm_to_gnd",
> +	"100kohm_to_gnd"
> +};
> +
> +static const struct iio_enum dac8854_powerdown_mode_enum = {
> +	.items = dac8554_powerdown_modes,
> +	.num_items = ARRAY_SIZE(dac8554_powerdown_modes),
> +	.get = dac8554_get_powerdown_mode,
> +	.set = dac8554_set_powerdown_mode,
> +};
> +
> +static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
> +	{
> +		.name = "powerdown",
> +		.read = dac8554_read_dac_powerdown,
> +		.write = dac8554_write_dac_powerdown,
> +		.shared = IIO_SEPARATE,
> +	},
> +	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
> +		 &dac8854_powerdown_mode_enum),
> +	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
> +	{ },
> +};
> +
> +#define DAC8554_CHANNEL(chan) { \
> +	.type = IIO_VOLTAGE, \
> +	.indexed = 1, \
> +	.output = 1, \
> +	.channel = (chan), \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> +	.address = (chan), \
> +	.ext_info = dac8554_ext_info, \
> +}
> +const struct iio_chan_spec dac8554_channels[] = {
> +	DAC8554_CHANNEL(0),
> +	DAC8554_CHANNEL(1),
> +	DAC8554_CHANNEL(2),
> +	DAC8554_CHANNEL(3),
> +};
> +#undef DAC8554_CHANNEL
> +
> +static int dac8554_probe(struct spi_device *spi)
> +{
> +	struct dac8554_state *st;
> +	struct iio_dev *indio_dev;
> +	int ret, voltage_uv;
> +	u32 addr;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->name = DAC8554_DRIVERNAME;
> +	indio_dev->info = &dac8554_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = dac8554_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
> +
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	st = iio_priv(indio_dev);
> +
> +	if (!spi->dev.of_node) {
> +		dev_err(&spi->dev, "missing OF node");
> +		return -ENODEV;
> +	}
> +	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
> +	if (ret || addr < 0 || addr > 2) {
> +		dev_err(&spi->dev, "no or invalid chip address");
> +		return -ENODEV;
> +	}
> +
> +	st->spi = spi;
> +	st->addr = addr;
> +
According to your DT bindings, the regulator from property "vref-supply" should
be used. This is missing here.
> +	st->reg = devm_regulator_get(&spi->dev, "vref");
> +	if (IS_ERR(st->reg))
> +		return PTR_ERR(st->reg);
> +
> +	ret = regulator_enable(st->reg);
> +	if (ret)
> +		return ret;
> +
> +	voltage_uv = regulator_get_voltage(st->reg);
> +	if (voltage_uv < 0)
> +		goto error_disable_reg;
Missing ret = voltage_uv before goto. Or just drop voltage_uv completely and use ret instead.
> +	st->vref_mv = voltage_uv / 1000;
How hard do you want to depend on a voltage regulator? Doing regulator_get_voltage()
could even be called dynamically in _read_raw(), making a real regulator optional.
> +
> +	ret = dac8554_powerdown(st, DAC8554_PWRDN_100K);
> +	if (ret)
> +		goto error_disable_reg;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret)
> +		goto error_disable_reg;
> +
> +	return 0;
> +
> +error_disable_reg:
> +	regulator_disable(st->reg);
> +	return ret;
> +}
> +
> +static int dac8554_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +	regulator_disable(st->reg);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id dac8554_of_match[] = {
> +	{ .compatible = "ti,dac8554" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, dac8554_of_match);
> +
> +static struct spi_driver dac8554_driver = {
> +	.driver = {
> +		.name = DAC8554_DRIVERNAME,
> +		.owner = THIS_MODULE,
> +		.of_match_table = dac8554_of_match,
> +	 },
> +	.probe = dac8554_probe,
> +	.remove = dac8554_remove,
> +};
> +module_spi_driver(dac8554_driver);
> +
> +MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>");
> +MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
> +MODULE_LICENSE("GPL v2");
> 

Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Jonathan Cameron]

On 06/12/14 11:36, Hartmut Knaack wrote:
> Nikolaus Schulz schrieb am 24.11.2014 um 20:50:
>> The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
>> interface.
>>
>> Changes in v2:
>> * Use DMA-safe buffer for SPI transfer
>> * Normalize powerdown_mode name "hi-z" to "three_state" as per
>>   ABI/testing/sysfs-bus-iio
>> * Register device late in probe function
>> * Avoid powerdown broadcast update, which touches all DAC on the bus
> There are a few issues left, please see my comments inline.
1 little one from me...
>>
>> Signed-off-by: Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
>> ---
>>  drivers/iio/dac/Kconfig      |  10 ++
>>  drivers/iio/dac/Makefile     |   1 +
>>  drivers/iio/dac/ti-dac8554.c | 374 +++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 385 insertions(+)
>>  create mode 100644 drivers/iio/dac/ti-dac8554.c
>>
>> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
>> index 2236ea2..1689260 100644
>> --- a/drivers/iio/dac/Kconfig
>> +++ b/drivers/iio/dac/Kconfig
>> @@ -181,4 +181,14 @@ config MCP4922
>>  	  To compile this driver as a module, choose M here: the module
>>  	  will be called mcp4922.
>>  
>> +config TI_DAC8554
>> +	tristate "TI DAC8554 driver"
>> +	depends on SPI
>> +	depends on OF
>> +	help
>> +	  Say yes here to build the driver for the TI DAC8554.
>> +
>> +	  To compile this driver as a module, choose M here: the module
>> +	  will be called ti-dac8554.
>> +
>>  endmenu
>> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
>> index 52be7e1..b98d79a 100644
>> --- a/drivers/iio/dac/Makefile
>> +++ b/drivers/iio/dac/Makefile
>> @@ -20,3 +20,4 @@ obj-$(CONFIG_MAX517) += max517.o
>>  obj-$(CONFIG_MAX5821) += max5821.o
>>  obj-$(CONFIG_MCP4725) += mcp4725.o
>>  obj-$(CONFIG_MCP4922) += mcp4922.o
>> +obj-$(CONFIG_TI_DAC8554) += ti-dac8554.o
>> diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
>> new file mode 100644
>> index 0000000..fca751f
>> --- /dev/null
>> +++ b/drivers/iio/dac/ti-dac8554.c
>> @@ -0,0 +1,374 @@
>> +/*
>> + * TI DAC8554 Digital to Analog Converter SPI driver
>> + *
>> + * Copyright (C) 2014 Avionic Design GmbH
>> + *
>> + * Based on ad5446r_spi.c
>> + * Copyright (C) 2010,2011 Analog Devices Inc.
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +
>> +#include <linux/spi/spi.h>
>> +#include <linux/regulator/consumer.h>
>> +#include <linux/module.h>
>> +#include <linux/iio/iio.h>
>> +#include <linux/of.h>
>> +
>> +#define DAC8554_DRIVERNAME			"ti-dac8554"
>> +#define DAC8554_DAC_CHANNELS			4
>> +
>> +/* Load commands */
>> +#define DAC8554_CMD_STORE_DAC_N			0x0
>> +#define DAC8554_CMD_UPDATE_DAC_N		0x1
>> +#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
>> +#define DAC8554_CMD_UPDATE_BROADCAST		0x3
>> +
>> +#define DAC8554_BROADCAST_USE_SRDATA		0x2
> Add a blank line here.
>> +/* Powerdown modes (ORed PD1|PD2 bits) */
> It took my some time to figure out ORed. I think you could drop it and just
> mention (PD1 | PD2 bits).
>> +#define DAC8554_PWRDN_HIZ			0x0
>> +#define DAC8554_PWRDN_1K			0x1
>> +#define DAC8554_PWRDN_100K			0x2
>> +
>> +#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
>> +
>> +/**
>> + * struct dac8554_state - driver instance specific data
>> + * @spi:		spi_device
> SPI device?
>> + * @reg:		supply regulator
>> + * @addr:		two-bit chip address
>> + * @vref_mv:		reference voltage in millivolt
>> + * @val			DAC/channel data
> DAC channel data?
>> + * @powerdown		channel powerdown flag
>> + * @powerdown_mode	channel powerdown mode
>> + * @xfer		SPI transfer buffer
> Half of the comments are with colon, the other half are missing it.
>> + */
>> +struct dac8554_state {
>> +	struct spi_device		*spi;
>> +	struct regulator		*reg;
>> +	unsigned			addr;
>> +	unsigned			vref_mv;
>> +	u16				val[DAC8554_DAC_CHANNELS];
>> +	bool				powerdown[DAC8554_DAC_CHANNELS];
>> +	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
>> +
>> +	/*
>> +	 * DMA (thus cache coherency maintenance) requires the
>> +	 * transfer buffers to live in their own cache lines.
>> +	 */
>> +	u8				xfer[3] ____cacheline_aligned;
>> +};
>> +
>> +static int dac8554_spi_write(struct dac8554_state *st,
>> +			     unsigned cmd,
>> +			     unsigned chan_addr,
>> +			     unsigned val)
>> +{
>> +	u32 data;
>> +
>> +	/*
>> +	 * The input shift register is 24 bits wide. The 8 MSB are
>> +	 * control bits, followed by 16 data bits.
>> +	 * The first two bits A1 and A0 address a DAC8554 chip.
>> +	 * The next two are the command bits, LD1 and LD0.
>> +	 * After a don't-care-bit, the next two bits select the channel.
>> +	 * The final control bit PD0 is a flag signalling if the data
>> +	 * bits encode a powerdown mode. We merge PD0 with the adjacent
>> +	 * data bits.
>> +	 */
>> +
>> +	if (cmd > 3 || chan_addr > 3 ||
>> +			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
>> +		return -EINVAL;
>> +
>> +	data = (st->addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
> Could be more readable by using definition for the magic shifts, or macros.
>> +	st->xfer[0] = data >> 16;
>> +	st->xfer[1] = data >> 8;
>> +	st->xfer[2] = data;
>> +
>> +	return spi_write(st->spi, st->xfer, sizeof(st->xfer));
>> +}
>> +
>> +static int dac8554_read_raw(struct iio_dev *indio_dev,
>> +			    struct iio_chan_spec const *chan,
>> +			    int *val,
>> +			    int *val2,
>> +			    long m)
> Commonly, m is called mask (like you do in _write_raw).
>> +{
>> +	struct dac8554_state *st = iio_priv(indio_dev);
>> +
>> +	switch (m) {
>> +	case IIO_CHAN_INFO_RAW:
>> +		*val = st->val[chan->address];
>> +		return IIO_VAL_INT;
>> +	case IIO_CHAN_INFO_SCALE:
>> +		*val = st->vref_mv;
>> +		*val2 = 16;
>> +		return IIO_VAL_FRACTIONAL_LOG2;
>> +	}
>> +	return -EINVAL;
>> +}
>> +
>> +static int dac8554_write_raw(struct iio_dev *indio_dev,
>> +			     struct iio_chan_spec const *chan,
>> +			     int val,
>> +			     int val2,
>> +			     long mask)
>> +{
>> +	struct dac8554_state *st = iio_priv(indio_dev);
>> +	int err;
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_RAW:
>> +		if (val > 0xffff || val < 0)
>> +			return -EINVAL;
>> +
>> +		err = dac8554_spi_write(st, DAC8554_CMD_UPDATE_DAC_N,
>> +					chan->address, val);
>> +		if (err)
>> +			return err;
>> +
>> +		st->val[chan->address] = val;
>> +
>> +		/* By hw design, DAC updates automatically trigger powerup. */
>> +		st->powerdown[chan->address] = false;
>> +
>> +		return 0;
>> +
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +}
>> +
>> +static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
>> +				      const struct iio_chan_spec *chan)
>> +{
>> +	struct dac8554_state *st = iio_priv(indio_dev);
>> +
>> +	return st->powerdown_mode[chan->address];
>> +}
>> +
>> +static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
>> +				      const struct iio_chan_spec *chan,
>> +				      unsigned int mode)
>> +{
>> +	struct dac8554_state *st = iio_priv(indio_dev);
>> +
>> +	st->powerdown_mode[chan->address] = mode;
>> +
>> +	return 0;
>> +}
>> +
>> +static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
>> +					  uintptr_t private,
>> +					  const struct iio_chan_spec *chan,
>> +					  char *buf)
>> +{
>> +	struct dac8554_state *st = iio_priv(indio_dev);
>> +
>> +	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
>> +}
>> +
>> +static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
>> +					   uintptr_t private,
>> +					   const struct iio_chan_spec *chan,
>> +					   const char *buf,
>> +					   size_t len)
>> +{
>> +	bool powerdown;
>> +	int ret;
>> +	struct dac8554_state *st = iio_priv(indio_dev);
>> +	u8 powerdown_mode;
>> +
>> +	ret = strtobool(buf, &powerdown);
>> +	if (ret)
>> +		return ret;
>> +
>> +	st->powerdown[chan->address] = powerdown;
>> +
>> +	if (powerdown) {
>> +		powerdown_mode = st->powerdown_mode[chan->address];
>> +		ret = dac8554_spi_write(st,
>> +				DAC8554_CMD_UPDATE_DAC_N,
>> +				chan->address,
>> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
> The parameters sill fit on line even with proper indentation.
>> +	} else {
>> +		/* Load DAC with cached value. This triggers a powerup. */
>> +		ret = dac8554_spi_write(st,
>> +				DAC8554_CMD_UPDATE_DAC_N,
>> +				chan->address,
>> +				st->val[chan->address]);
> Same here with indentation.
>> +	}
>> +
>> +	if (ret)
>> +		return ret;
>> +
>> +	return len;
> Just: return (ret) ? ret : len;
>> +}
>> +
>> +static int dac8554_powerdown(struct dac8554_state *st,
>> +			     u8 powerdown_mode)
>> +{
>> +	int chan, cmd, ret;
>> +
>> +	for (chan = DAC8554_DAC_CHANNELS-1; chan >= 0; --chan) {
> Please mind spaces around operators.
>> +		cmd = chan ? DAC8554_CMD_STORE_DAC_N
>> +			   : DAC8554_CMD_STORE_DAC_N_UPDATE_ALL;
>> +		ret = dac8554_spi_write(st, cmd, chan,
>> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>> +	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
>> +	memset(st->powerdown, true, sizeof(st->powerdown));
Whilst this probably works, I think for the boolean case it is less
than entirely obvious, so probably better to have a simple loop.
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct iio_info dac8554_info = {
>> +	.write_raw = dac8554_write_raw,
>> +	.read_raw = dac8554_read_raw,
>> +	.driver_module = THIS_MODULE,
>> +};
>> +
>> +static const char * const dac8554_powerdown_modes[] = {
>> +	"three_state",
>> +	"1kohm_to_gnd",
>> +	"100kohm_to_gnd"
>> +};
>> +
>> +static const struct iio_enum dac8854_powerdown_mode_enum = {
>> +	.items = dac8554_powerdown_modes,
>> +	.num_items = ARRAY_SIZE(dac8554_powerdown_modes),
>> +	.get = dac8554_get_powerdown_mode,
>> +	.set = dac8554_set_powerdown_mode,
>> +};
>> +
>> +static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
>> +	{
>> +		.name = "powerdown",
>> +		.read = dac8554_read_dac_powerdown,
>> +		.write = dac8554_write_dac_powerdown,
>> +		.shared = IIO_SEPARATE,
>> +	},
>> +	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
>> +		 &dac8854_powerdown_mode_enum),
>> +	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
>> +	{ },
>> +};
>> +
>> +#define DAC8554_CHANNEL(chan) { \
>> +	.type = IIO_VOLTAGE, \
>> +	.indexed = 1, \
>> +	.output = 1, \
>> +	.channel = (chan), \
>> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
>> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
>> +	.address = (chan), \
>> +	.ext_info = dac8554_ext_info, \
>> +}
>> +const struct iio_chan_spec dac8554_channels[] = {
>> +	DAC8554_CHANNEL(0),
>> +	DAC8554_CHANNEL(1),
>> +	DAC8554_CHANNEL(2),
>> +	DAC8554_CHANNEL(3),
>> +};
>> +#undef DAC8554_CHANNEL
>> +
>> +static int dac8554_probe(struct spi_device *spi)
>> +{
>> +	struct dac8554_state *st;
>> +	struct iio_dev *indio_dev;
>> +	int ret, voltage_uv;
>> +	u32 addr;
>> +
>> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
>> +	if (!indio_dev)
>> +		return -ENOMEM;
>> +
>> +	indio_dev->dev.parent = &spi->dev;
>> +	indio_dev->name = DAC8554_DRIVERNAME;
>> +	indio_dev->info = &dac8554_info;
>> +	indio_dev->modes = INDIO_DIRECT_MODE;
>> +	indio_dev->channels = dac8554_channels;
>> +	indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
>> +
>> +	spi_set_drvdata(spi, indio_dev);
>> +
>> +	st = iio_priv(indio_dev);
>> +
>> +	if (!spi->dev.of_node) {
>> +		dev_err(&spi->dev, "missing OF node");
>> +		return -ENODEV;
>> +	}
>> +	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
>> +	if (ret || addr < 0 || addr > 2) {
>> +		dev_err(&spi->dev, "no or invalid chip address");
>> +		return -ENODEV;
>> +	}
>> +
>> +	st->spi = spi;
>> +	st->addr = addr;
>> +
> According to your DT bindings, the regulator from property "vref-supply" should
> be used. This is missing here.
>> +	st->reg = devm_regulator_get(&spi->dev, "vref");
>> +	if (IS_ERR(st->reg))
>> +		return PTR_ERR(st->reg);
>> +
>> +	ret = regulator_enable(st->reg);
>> +	if (ret)
>> +		return ret;
>> +
>> +	voltage_uv = regulator_get_voltage(st->reg);
>> +	if (voltage_uv < 0)
>> +		goto error_disable_reg;
> Missing ret = voltage_uv before goto. Or just drop voltage_uv completely and use ret instead.
>> +	st->vref_mv = voltage_uv / 1000;
> How hard do you want to depend on a voltage regulator? Doing regulator_get_voltage()
> could even be called dynamically in _read_raw(), making a real regulator optional.
>> +
>> +	ret = dac8554_powerdown(st, DAC8554_PWRDN_100K);
>> +	if (ret)
>> +		goto error_disable_reg;
>> +
>> +	ret = iio_device_register(indio_dev);
>> +	if (ret)
>> +		goto error_disable_reg;
>> +
>> +	return 0;
>> +
>> +error_disable_reg:
>> +	regulator_disable(st->reg);
>> +	return ret;
>> +}
>> +
>> +static int dac8554_remove(struct spi_device *spi)
>> +{
>> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
>> +	struct dac8554_state *st = iio_priv(indio_dev);
>> +
>> +	iio_device_unregister(indio_dev);
>> +	regulator_disable(st->reg);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id dac8554_of_match[] = {
>> +	{ .compatible = "ti,dac8554" },
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(of, dac8554_of_match);
>> +
>> +static struct spi_driver dac8554_driver = {
>> +	.driver = {
>> +		.name = DAC8554_DRIVERNAME,
>> +		.owner = THIS_MODULE,
>> +		.of_match_table = dac8554_of_match,
>> +	 },
>> +	.probe = dac8554_probe,
>> +	.remove = dac8554_remove,
>> +};
>> +module_spi_driver(dac8554_driver);
>> +
>> +MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>");
>> +MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
>> +MODULE_LICENSE("GPL v2");
>>
> 
> --
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> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Nikolaus Schulz]

On Sat, Dec 06, 2014 at 12:36:19PM +0100, Hartmut Knaack wrote:
> Nikolaus Schulz schrieb am 24.11.2014 um 20:50:
> > The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
> > interface.
> > 
> > Changes in v2:
> > * Use DMA-safe buffer for SPI transfer
> > * Normalize powerdown_mode name "hi-z" to "three_state" as per
> >   ABI/testing/sysfs-bus-iio
> > * Register device late in probe function
> > * Avoid powerdown broadcast update, which touches all DAC on the bus
> There are a few issues left, please see my comments inline.
> > 
> > Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
> > ---
> >  drivers/iio/dac/Kconfig      |  10 ++
> >  drivers/iio/dac/Makefile     |   1 +
> >  drivers/iio/dac/ti-dac8554.c | 374 +++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 385 insertions(+)
> >  create mode 100644 drivers/iio/dac/ti-dac8554.c
[...]
> > diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
> > new file mode 100644
> > index 0000000..fca751f
> > --- /dev/null
> > +++ b/drivers/iio/dac/ti-dac8554.c
> > @@ -0,0 +1,374 @@
> > +/*
> > + * TI DAC8554 Digital to Analog Converter SPI driver
> > + *
> > + * Copyright (C) 2014 Avionic Design GmbH
> > + *
> > + * Based on ad5446r_spi.c
> > + * Copyright (C) 2010,2011 Analog Devices Inc.
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + */
> > +
> > +#include <linux/spi/spi.h>
> > +#include <linux/regulator/consumer.h>
> > +#include <linux/module.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/of.h>
> > +
> > +#define DAC8554_DRIVERNAME			"ti-dac8554"
> > +#define DAC8554_DAC_CHANNELS			4
> > +
> > +/* Load commands */
> > +#define DAC8554_CMD_STORE_DAC_N			0x0
> > +#define DAC8554_CMD_UPDATE_DAC_N		0x1
> > +#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
> > +#define DAC8554_CMD_UPDATE_BROADCAST		0x3
> > +
> > +#define DAC8554_BROADCAST_USE_SRDATA		0x2
> Add a blank line here.

Fixed.

> > +/* Powerdown modes (ORed PD1|PD2 bits) */
> It took my some time to figure out ORed. I think you could drop it and just
> mention (PD1 | PD2 bits).

Agreed, and fixed.

> > +#define DAC8554_PWRDN_HIZ			0x0
> > +#define DAC8554_PWRDN_1K			0x1
> > +#define DAC8554_PWRDN_100K			0x2
> > +
> > +#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
> > +
> > +/**
> > + * struct dac8554_state - driver instance specific data
> > + * @spi:		spi_device
> SPI device?

Yes, fixed.

> > + * @reg:		supply regulator
> > + * @addr:		two-bit chip address
> > + * @vref_mv:		reference voltage in millivolt
> > + * @val			DAC/channel data
> DAC channel data?

"channel data" will do, actually.

> > + * @powerdown		channel powerdown flag
> > + * @powerdown_mode	channel powerdown mode
> > + * @xfer		SPI transfer buffer
> Half of the comments are with colon, the other half are missing it.

Fixed.

> > + */
> > +struct dac8554_state {
> > +	struct spi_device		*spi;
> > +	struct regulator		*reg;
> > +	unsigned			addr;
> > +	unsigned			vref_mv;
> > +	u16				val[DAC8554_DAC_CHANNELS];
> > +	bool				powerdown[DAC8554_DAC_CHANNELS];
> > +	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
> > +
> > +	/*
> > +	 * DMA (thus cache coherency maintenance) requires the
> > +	 * transfer buffers to live in their own cache lines.
> > +	 */
> > +	u8				xfer[3] ____cacheline_aligned;
> > +};
> > +
> > +static int dac8554_spi_write(struct dac8554_state *st,
> > +			     unsigned cmd,
> > +			     unsigned chan_addr,
> > +			     unsigned val)
> > +{
> > +	u32 data;
> > +
> > +	/*
> > +	 * The input shift register is 24 bits wide. The 8 MSB are
> > +	 * control bits, followed by 16 data bits.
> > +	 * The first two bits A1 and A0 address a DAC8554 chip.
> > +	 * The next two are the command bits, LD1 and LD0.
> > +	 * After a don't-care-bit, the next two bits select the channel.
> > +	 * The final control bit PD0 is a flag signalling if the data
> > +	 * bits encode a powerdown mode. We merge PD0 with the adjacent
> > +	 * data bits.
> > +	 */
> > +
> > +	if (cmd > 3 || chan_addr > 3 ||
> > +			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
> > +		return -EINVAL;
> > +
> > +	data = (st->addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
> Could be more readable by using definition for the magic shifts, or macros.

Hmm. The magic is all concentrated at this place, and the variable names
tell the story, so I figured that's ok.  But, why not: fixed.

> > +	st->xfer[0] = data >> 16;
> > +	st->xfer[1] = data >> 8;
> > +	st->xfer[2] = data;
> > +
> > +	return spi_write(st->spi, st->xfer, sizeof(st->xfer));
> > +}
> > +
> > +static int dac8554_read_raw(struct iio_dev *indio_dev,
> > +			    struct iio_chan_spec const *chan,
> > +			    int *val,
> > +			    int *val2,
> > +			    long m)
> Commonly, m is called mask (like you do in _write_raw).

Ah yes. Fixed.

> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	switch (m) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		*val = st->val[chan->address];
> > +		return IIO_VAL_INT;
> > +	case IIO_CHAN_INFO_SCALE:
> > +		*val = st->vref_mv;
> > +		*val2 = 16;
> > +		return IIO_VAL_FRACTIONAL_LOG2;
> > +	}
> > +	return -EINVAL;
> > +}
> > +
> > +static int dac8554_write_raw(struct iio_dev *indio_dev,
> > +			     struct iio_chan_spec const *chan,
> > +			     int val,
> > +			     int val2,
> > +			     long mask)
> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +	int err;
> > +
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		if (val > 0xffff || val < 0)
> > +			return -EINVAL;
> > +
> > +		err = dac8554_spi_write(st, DAC8554_CMD_UPDATE_DAC_N,
> > +					chan->address, val);
> > +		if (err)
> > +			return err;
> > +
> > +		st->val[chan->address] = val;
> > +
> > +		/* By hw design, DAC updates automatically trigger powerup. */
> > +		st->powerdown[chan->address] = false;
> > +
> > +		return 0;
> > +
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> > +static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
> > +				      const struct iio_chan_spec *chan)
> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	return st->powerdown_mode[chan->address];
> > +}
> > +
> > +static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
> > +				      const struct iio_chan_spec *chan,
> > +				      unsigned int mode)
> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	st->powerdown_mode[chan->address] = mode;
> > +
> > +	return 0;
> > +}
> > +
> > +static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
> > +					  uintptr_t private,
> > +					  const struct iio_chan_spec *chan,
> > +					  char *buf)
> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
> > +}
> > +
> > +static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
> > +					   uintptr_t private,
> > +					   const struct iio_chan_spec *chan,
> > +					   const char *buf,
> > +					   size_t len)
> > +{
> > +	bool powerdown;
> > +	int ret;
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +	u8 powerdown_mode;
> > +
> > +	ret = strtobool(buf, &powerdown);
> > +	if (ret)
> > +		return ret;
> > +
> > +	st->powerdown[chan->address] = powerdown;
> > +
> > +	if (powerdown) {
> > +		powerdown_mode = st->powerdown_mode[chan->address];
> > +		ret = dac8554_spi_write(st,
> > +				DAC8554_CMD_UPDATE_DAC_N,
> > +				chan->address,
> > +				DAC8554_PWRDN_TO_SR(powerdown_mode));
> The parameters sill fit on line even with proper indentation.

Fixed.

> > +	} else {
> > +		/* Load DAC with cached value. This triggers a powerup. */
> > +		ret = dac8554_spi_write(st,
> > +				DAC8554_CMD_UPDATE_DAC_N,
> > +				chan->address,
> > +				st->val[chan->address]);
> Same here with indentation.

Fixed.

> > +	}
> > +
> > +	if (ret)
> > +		return ret;
> > +
> > +	return len;
> Just: return (ret) ? ret : len;

I think avoiding the ternary operator makes the code more readable, and
it separates the error path from normal operation. So I would prefer to
keep it that way.

> > +}
> > +
> > +static int dac8554_powerdown(struct dac8554_state *st,
> > +			     u8 powerdown_mode)
> > +{
> > +	int chan, cmd, ret;
> > +
> > +	for (chan = DAC8554_DAC_CHANNELS-1; chan >= 0; --chan) {
> Please mind spaces around operators.

Fixed.

> > +		cmd = chan ? DAC8554_CMD_STORE_DAC_N
> > +			   : DAC8554_CMD_STORE_DAC_N_UPDATE_ALL;
> > +		ret = dac8554_spi_write(st, cmd, chan,
> > +				DAC8554_PWRDN_TO_SR(powerdown_mode));
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
> > +	memset(st->powerdown, true, sizeof(st->powerdown));
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct iio_info dac8554_info = {
> > +	.write_raw = dac8554_write_raw,
> > +	.read_raw = dac8554_read_raw,
> > +	.driver_module = THIS_MODULE,
> > +};
> > +
> > +static const char * const dac8554_powerdown_modes[] = {
> > +	"three_state",
> > +	"1kohm_to_gnd",
> > +	"100kohm_to_gnd"
> > +};
> > +
> > +static const struct iio_enum dac8854_powerdown_mode_enum = {
> > +	.items = dac8554_powerdown_modes,
> > +	.num_items = ARRAY_SIZE(dac8554_powerdown_modes),
> > +	.get = dac8554_get_powerdown_mode,
> > +	.set = dac8554_set_powerdown_mode,
> > +};
> > +
> > +static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
> > +	{
> > +		.name = "powerdown",
> > +		.read = dac8554_read_dac_powerdown,
> > +		.write = dac8554_write_dac_powerdown,
> > +		.shared = IIO_SEPARATE,
> > +	},
> > +	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
> > +		 &dac8854_powerdown_mode_enum),
> > +	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
> > +	{ },
> > +};
> > +
> > +#define DAC8554_CHANNEL(chan) { \
> > +	.type = IIO_VOLTAGE, \
> > +	.indexed = 1, \
> > +	.output = 1, \
> > +	.channel = (chan), \
> > +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> > +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> > +	.address = (chan), \
> > +	.ext_info = dac8554_ext_info, \
> > +}
> > +const struct iio_chan_spec dac8554_channels[] = {
> > +	DAC8554_CHANNEL(0),
> > +	DAC8554_CHANNEL(1),
> > +	DAC8554_CHANNEL(2),
> > +	DAC8554_CHANNEL(3),
> > +};
> > +#undef DAC8554_CHANNEL
> > +
> > +static int dac8554_probe(struct spi_device *spi)
> > +{
> > +	struct dac8554_state *st;
> > +	struct iio_dev *indio_dev;
> > +	int ret, voltage_uv;
> > +	u32 addr;
> > +
> > +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> > +	if (!indio_dev)
> > +		return -ENOMEM;
> > +
> > +	indio_dev->dev.parent = &spi->dev;
> > +	indio_dev->name = DAC8554_DRIVERNAME;
> > +	indio_dev->info = &dac8554_info;
> > +	indio_dev->modes = INDIO_DIRECT_MODE;
> > +	indio_dev->channels = dac8554_channels;
> > +	indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
> > +
> > +	spi_set_drvdata(spi, indio_dev);
> > +
> > +	st = iio_priv(indio_dev);
> > +
> > +	if (!spi->dev.of_node) {
> > +		dev_err(&spi->dev, "missing OF node");
> > +		return -ENODEV;
> > +	}
> > +	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
> > +	if (ret || addr < 0 || addr > 2) {
> > +		dev_err(&spi->dev, "no or invalid chip address");
> > +		return -ENODEV;
> > +	}
> > +
> > +	st->spi = spi;
> > +	st->addr = addr;
> > +
> According to your DT bindings, the regulator from property "vref-supply" should
> be used. This is missing here.

Uhm, it's right below, no?

> > +	st->reg = devm_regulator_get(&spi->dev, "vref");
> > +	if (IS_ERR(st->reg))
> > +		return PTR_ERR(st->reg);
> > +
> > +	ret = regulator_enable(st->reg);
> > +	if (ret)
> > +		return ret;
> > +
> > +	voltage_uv = regulator_get_voltage(st->reg);
> > +	if (voltage_uv < 0)
> > +		goto error_disable_reg;
> Missing ret = voltage_uv before goto. Or just drop voltage_uv completely and use ret instead.

Fixed.

> > +	st->vref_mv = voltage_uv / 1000;
> How hard do you want to depend on a voltage regulator? Doing regulator_get_voltage()
> could even be called dynamically in _read_raw(), making a real regulator optional.

Hmm. I understand that the DAC voltage input may not be provided by a
regulator, but is that a common scenario?  No other DAC driver I looked
at handles that case, they all consider it an error if the regulator is
absent.

> > +
> > +	ret = dac8554_powerdown(st, DAC8554_PWRDN_100K);
> > +	if (ret)
> > +		goto error_disable_reg;
> > +
> > +	ret = iio_device_register(indio_dev);
> > +	if (ret)
> > +		goto error_disable_reg;
> > +
> > +	return 0;
> > +
> > +error_disable_reg:
> > +	regulator_disable(st->reg);
> > +	return ret;
> > +}
> > +
> > +static int dac8554_remove(struct spi_device *spi)
> > +{
> > +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	iio_device_unregister(indio_dev);
> > +	regulator_disable(st->reg);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct of_device_id dac8554_of_match[] = {
> > +	{ .compatible = "ti,dac8554" },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(of, dac8554_of_match);
> > +
> > +static struct spi_driver dac8554_driver = {
> > +	.driver = {
> > +		.name = DAC8554_DRIVERNAME,
> > +		.owner = THIS_MODULE,
> > +		.of_match_table = dac8554_of_match,
> > +	 },
> > +	.probe = dac8554_probe,
> > +	.remove = dac8554_remove,
> > +};
> > +module_spi_driver(dac8554_driver);
> > +
> > +MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz@avionic-design.de>");
> > +MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
> > +MODULE_LICENSE("GPL v2");

Thanks for the review!

Nikolaus
-- 
Avionic Design GmbH
Nikolaus Schulz
Wragekamp 10
D-22397 Hamburg
Germany

Tel.:  +49 40 88187-163
Fax:   +49 40 88187-150
Email: nikolaus.schulz@avionic-design.de

Avionic Design GmbH
Amtsgericht Hamburg HRB 82598
Geschäftsführung: Cornelis Broers
Ust.-Ident-Nr.: DE813378254

Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Nikolaus Schulz]

On Fri, Dec 12, 2014 at 11:57:08AM +0000, Jonathan Cameron wrote:
> On 06/12/14 11:36, Hartmut Knaack wrote:
> > Nikolaus Schulz schrieb am 24.11.2014 um 20:50:
> >> The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
> >> interface.
> >>
> >> Changes in v2:
> >> * Use DMA-safe buffer for SPI transfer
> >> * Normalize powerdown_mode name "hi-z" to "three_state" as per
> >>   ABI/testing/sysfs-bus-iio
> >> * Register device late in probe function
> >> * Avoid powerdown broadcast update, which touches all DAC on the bus
> > There are a few issues left, please see my comments inline.
> 1 little one from me...
> >>
> >> Signed-off-by: Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
> >> ---
> >>  drivers/iio/dac/Kconfig      |  10 ++
> >>  drivers/iio/dac/Makefile     |   1 +
> >>  drivers/iio/dac/ti-dac8554.c | 374 +++++++++++++++++++++++++++++++++++++++++++
> >>  3 files changed, 385 insertions(+)
> >>  create mode 100644 drivers/iio/dac/ti-dac8554.c
[...]
> >> diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
> >> new file mode 100644
> >> index 0000000..fca751f
> >> --- /dev/null
> >> +++ b/drivers/iio/dac/ti-dac8554.c
[...]
> >> +static int dac8554_powerdown(struct dac8554_state *st,
> >> +			     u8 powerdown_mode)
> >> +{
> >> +	int chan, cmd, ret;
> >> +
> >> +	for (chan = DAC8554_DAC_CHANNELS-1; chan >= 0; --chan) {
> > Please mind spaces around operators.
> >> +		cmd = chan ? DAC8554_CMD_STORE_DAC_N
> >> +			   : DAC8554_CMD_STORE_DAC_N_UPDATE_ALL;
> >> +		ret = dac8554_spi_write(st, cmd, chan,
> >> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
> >> +		if (ret)
> >> +			return ret;
> >> +	}
> >> +
> >> +	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
> >> +	memset(st->powerdown, true, sizeof(st->powerdown));
> Whilst this probably works, I think for the boolean case it is less
> than entirely obvious, so probably better to have a simple loop.

Yeah, I agree it's better to keep it as simple and obvious as possible.
Fixed in v3.

> >> +
> >> +	return 0;
> >> +}

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Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Jonathan Cameron]

On 12/12/14 15:58, Nikolaus Schulz wrote:
> On Sat, Dec 06, 2014 at 12:36:19PM +0100, Hartmut Knaack wrote:
>> Nikolaus Schulz schrieb am 24.11.2014 um 20:50:
>>> The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
>>> interface.
>>>
>>> Changes in v2:
>>> * Use DMA-safe buffer for SPI transfer
>>> * Normalize powerdown_mode name "hi-z" to "three_state" as per
>>>   ABI/testing/sysfs-bus-iio
>>> * Register device late in probe function
>>> * Avoid powerdown broadcast update, which touches all DAC on the bus
>> There are a few issues left, please see my comments inline.
>>>
>>> Signed-off-by: Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
>>> ---
>>>  drivers/iio/dac/Kconfig      |  10 ++
>>>  drivers/iio/dac/Makefile     |   1 +
>>>  drivers/iio/dac/ti-dac8554.c | 374 +++++++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 385 insertions(+)
>>>  create mode 100644 drivers/iio/dac/ti-dac8554.c
> [...]
>>> diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
>>> new file mode 100644
>>> index 0000000..fca751f
>>> --- /dev/null
>>> +++ b/drivers/iio/dac/ti-dac8554.c
>>> @@ -0,0 +1,374 @@
>>> +/*
>>> + * TI DAC8554 Digital to Analog Converter SPI driver
>>> + *
>>> + * Copyright (C) 2014 Avionic Design GmbH
>>> + *
>>> + * Based on ad5446r_spi.c
>>> + * Copyright (C) 2010,2011 Analog Devices Inc.
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + */
>>> +
>>> +#include <linux/spi/spi.h>
>>> +#include <linux/regulator/consumer.h>
>>> +#include <linux/module.h>
>>> +#include <linux/iio/iio.h>
>>> +#include <linux/of.h>
>>> +
>>> +#define DAC8554_DRIVERNAME			"ti-dac8554"
>>> +#define DAC8554_DAC_CHANNELS			4
>>> +
>>> +/* Load commands */
>>> +#define DAC8554_CMD_STORE_DAC_N			0x0
>>> +#define DAC8554_CMD_UPDATE_DAC_N		0x1
>>> +#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
>>> +#define DAC8554_CMD_UPDATE_BROADCAST		0x3
>>> +
>>> +#define DAC8554_BROADCAST_USE_SRDATA		0x2
>> Add a blank line here.
> 
> Fixed.
> 
>>> +/* Powerdown modes (ORed PD1|PD2 bits) */
>> It took my some time to figure out ORed. I think you could drop it and just
>> mention (PD1 | PD2 bits).
> 
> Agreed, and fixed.
> 
>>> +#define DAC8554_PWRDN_HIZ			0x0
>>> +#define DAC8554_PWRDN_1K			0x1
>>> +#define DAC8554_PWRDN_100K			0x2
>>> +
>>> +#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
>>> +
>>> +/**
>>> + * struct dac8554_state - driver instance specific data
>>> + * @spi:		spi_device
>> SPI device?
> 
> Yes, fixed.
> 
>>> + * @reg:		supply regulator
>>> + * @addr:		two-bit chip address
>>> + * @vref_mv:		reference voltage in millivolt
>>> + * @val			DAC/channel data
>> DAC channel data?
> 
> "channel data" will do, actually.
> 
>>> + * @powerdown		channel powerdown flag
>>> + * @powerdown_mode	channel powerdown mode
>>> + * @xfer		SPI transfer buffer
>> Half of the comments are with colon, the other half are missing it.
> 
> Fixed.
> 
>>> + */
>>> +struct dac8554_state {
>>> +	struct spi_device		*spi;
>>> +	struct regulator		*reg;
>>> +	unsigned			addr;
>>> +	unsigned			vref_mv;
>>> +	u16				val[DAC8554_DAC_CHANNELS];
>>> +	bool				powerdown[DAC8554_DAC_CHANNELS];
>>> +	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
>>> +
>>> +	/*
>>> +	 * DMA (thus cache coherency maintenance) requires the
>>> +	 * transfer buffers to live in their own cache lines.
>>> +	 */
>>> +	u8				xfer[3] ____cacheline_aligned;
>>> +};
>>> +
>>> +static int dac8554_spi_write(struct dac8554_state *st,
>>> +			     unsigned cmd,
>>> +			     unsigned chan_addr,
>>> +			     unsigned val)
>>> +{
>>> +	u32 data;
>>> +
>>> +	/*
>>> +	 * The input shift register is 24 bits wide. The 8 MSB are
>>> +	 * control bits, followed by 16 data bits.
>>> +	 * The first two bits A1 and A0 address a DAC8554 chip.
>>> +	 * The next two are the command bits, LD1 and LD0.
>>> +	 * After a don't-care-bit, the next two bits select the channel.
>>> +	 * The final control bit PD0 is a flag signalling if the data
>>> +	 * bits encode a powerdown mode. We merge PD0 with the adjacent
>>> +	 * data bits.
>>> +	 */
>>> +
>>> +	if (cmd > 3 || chan_addr > 3 ||
>>> +			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
>>> +		return -EINVAL;
>>> +
>>> +	data = (st->addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
>> Could be more readable by using definition for the magic shifts, or macros.
> 
> Hmm. The magic is all concentrated at this place, and the variable names
> tell the story, so I figured that's ok.  But, why not: fixed.
> 
>>> +	st->xfer[0] = data >> 16;
>>> +	st->xfer[1] = data >> 8;
>>> +	st->xfer[2] = data;
>>> +
>>> +	return spi_write(st->spi, st->xfer, sizeof(st->xfer));
>>> +}
>>> +
>>> +static int dac8554_read_raw(struct iio_dev *indio_dev,
>>> +			    struct iio_chan_spec const *chan,
>>> +			    int *val,
>>> +			    int *val2,
>>> +			    long m)
>> Commonly, m is called mask (like you do in _write_raw).
> 
> Ah yes. Fixed.
> 
>>> +{
>>> +	struct dac8554_state *st = iio_priv(indio_dev);
>>> +
>>> +	switch (m) {
>>> +	case IIO_CHAN_INFO_RAW:
>>> +		*val = st->val[chan->address];
>>> +		return IIO_VAL_INT;
>>> +	case IIO_CHAN_INFO_SCALE:
>>> +		*val = st->vref_mv;
>>> +		*val2 = 16;
>>> +		return IIO_VAL_FRACTIONAL_LOG2;
>>> +	}
>>> +	return -EINVAL;
>>> +}
>>> +
>>> +static int dac8554_write_raw(struct iio_dev *indio_dev,
>>> +			     struct iio_chan_spec const *chan,
>>> +			     int val,
>>> +			     int val2,
>>> +			     long mask)
>>> +{
>>> +	struct dac8554_state *st = iio_priv(indio_dev);
>>> +	int err;
>>> +
>>> +	switch (mask) {
>>> +	case IIO_CHAN_INFO_RAW:
>>> +		if (val > 0xffff || val < 0)
>>> +			return -EINVAL;
>>> +
>>> +		err = dac8554_spi_write(st, DAC8554_CMD_UPDATE_DAC_N,
>>> +					chan->address, val);
>>> +		if (err)
>>> +			return err;
>>> +
>>> +		st->val[chan->address] = val;
>>> +
>>> +		/* By hw design, DAC updates automatically trigger powerup. */
>>> +		st->powerdown[chan->address] = false;
>>> +
>>> +		return 0;
>>> +
>>> +	default:
>>> +		return -EINVAL;
>>> +	}
>>> +}
>>> +
>>> +static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
>>> +				      const struct iio_chan_spec *chan)
>>> +{
>>> +	struct dac8554_state *st = iio_priv(indio_dev);
>>> +
>>> +	return st->powerdown_mode[chan->address];
>>> +}
>>> +
>>> +static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
>>> +				      const struct iio_chan_spec *chan,
>>> +				      unsigned int mode)
>>> +{
>>> +	struct dac8554_state *st = iio_priv(indio_dev);
>>> +
>>> +	st->powerdown_mode[chan->address] = mode;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
>>> +					  uintptr_t private,
>>> +					  const struct iio_chan_spec *chan,
>>> +					  char *buf)
>>> +{
>>> +	struct dac8554_state *st = iio_priv(indio_dev);
>>> +
>>> +	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
>>> +}
>>> +
>>> +static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
>>> +					   uintptr_t private,
>>> +					   const struct iio_chan_spec *chan,
>>> +					   const char *buf,
>>> +					   size_t len)
>>> +{
>>> +	bool powerdown;
>>> +	int ret;
>>> +	struct dac8554_state *st = iio_priv(indio_dev);
>>> +	u8 powerdown_mode;
>>> +
>>> +	ret = strtobool(buf, &powerdown);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	st->powerdown[chan->address] = powerdown;
>>> +
>>> +	if (powerdown) {
>>> +		powerdown_mode = st->powerdown_mode[chan->address];
>>> +		ret = dac8554_spi_write(st,
>>> +				DAC8554_CMD_UPDATE_DAC_N,
>>> +				chan->address,
>>> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
>> The parameters sill fit on line even with proper indentation.
> 
> Fixed.
> 
>>> +	} else {
>>> +		/* Load DAC with cached value. This triggers a powerup. */
>>> +		ret = dac8554_spi_write(st,
>>> +				DAC8554_CMD_UPDATE_DAC_N,
>>> +				chan->address,
>>> +				st->val[chan->address]);
>> Same here with indentation.
> 
> Fixed.
> 
>>> +	}
>>> +
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	return len;
>> Just: return (ret) ? ret : len;
> 
> I think avoiding the ternary operator makes the code more readable, and
> it separates the error path from normal operation. So I would prefer to
> keep it that way.
Agreed. Matter of personal taste - personally I don't really care either
way ;)
> 
>>> +}
>>> +
>>> +static int dac8554_powerdown(struct dac8554_state *st,
>>> +			     u8 powerdown_mode)
>>> +{
>>> +	int chan, cmd, ret;
>>> +
>>> +	for (chan = DAC8554_DAC_CHANNELS-1; chan >= 0; --chan) {
>> Please mind spaces around operators.
> 
> Fixed.
> 
>>> +		cmd = chan ? DAC8554_CMD_STORE_DAC_N
>>> +			   : DAC8554_CMD_STORE_DAC_N_UPDATE_ALL;
>>> +		ret = dac8554_spi_write(st, cmd, chan,
>>> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
>>> +		if (ret)
>>> +			return ret;
>>> +	}
>>> +
>>> +	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
>>> +	memset(st->powerdown, true, sizeof(st->powerdown));
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static const struct iio_info dac8554_info = {
>>> +	.write_raw = dac8554_write_raw,
>>> +	.read_raw = dac8554_read_raw,
>>> +	.driver_module = THIS_MODULE,
>>> +};
>>> +
>>> +static const char * const dac8554_powerdown_modes[] = {
>>> +	"three_state",
>>> +	"1kohm_to_gnd",
>>> +	"100kohm_to_gnd"
>>> +};
>>> +
>>> +static const struct iio_enum dac8854_powerdown_mode_enum = {
>>> +	.items = dac8554_powerdown_modes,
>>> +	.num_items = ARRAY_SIZE(dac8554_powerdown_modes),
>>> +	.get = dac8554_get_powerdown_mode,
>>> +	.set = dac8554_set_powerdown_mode,
>>> +};
>>> +
>>> +static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
>>> +	{
>>> +		.name = "powerdown",
>>> +		.read = dac8554_read_dac_powerdown,
>>> +		.write = dac8554_write_dac_powerdown,
>>> +		.shared = IIO_SEPARATE,
>>> +	},
>>> +	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
>>> +		 &dac8854_powerdown_mode_enum),
>>> +	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
>>> +	{ },
>>> +};
>>> +
>>> +#define DAC8554_CHANNEL(chan) { \
>>> +	.type = IIO_VOLTAGE, \
>>> +	.indexed = 1, \
>>> +	.output = 1, \
>>> +	.channel = (chan), \
>>> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
>>> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
>>> +	.address = (chan), \
>>> +	.ext_info = dac8554_ext_info, \
>>> +}
>>> +const struct iio_chan_spec dac8554_channels[] = {
>>> +	DAC8554_CHANNEL(0),
>>> +	DAC8554_CHANNEL(1),
>>> +	DAC8554_CHANNEL(2),
>>> +	DAC8554_CHANNEL(3),
>>> +};
>>> +#undef DAC8554_CHANNEL
>>> +
>>> +static int dac8554_probe(struct spi_device *spi)
>>> +{
>>> +	struct dac8554_state *st;
>>> +	struct iio_dev *indio_dev;
>>> +	int ret, voltage_uv;
>>> +	u32 addr;
>>> +
>>> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
>>> +	if (!indio_dev)
>>> +		return -ENOMEM;
>>> +
>>> +	indio_dev->dev.parent = &spi->dev;
>>> +	indio_dev->name = DAC8554_DRIVERNAME;
>>> +	indio_dev->info = &dac8554_info;
>>> +	indio_dev->modes = INDIO_DIRECT_MODE;
>>> +	indio_dev->channels = dac8554_channels;
>>> +	indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
>>> +
>>> +	spi_set_drvdata(spi, indio_dev);
>>> +
>>> +	st = iio_priv(indio_dev);
>>> +
>>> +	if (!spi->dev.of_node) {
>>> +		dev_err(&spi->dev, "missing OF node");
>>> +		return -ENODEV;
>>> +	}
>>> +	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
>>> +	if (ret || addr < 0 || addr > 2) {
>>> +		dev_err(&spi->dev, "no or invalid chip address");
>>> +		return -ENODEV;
>>> +	}
>>> +
>>> +	st->spi = spi;
>>> +	st->addr = addr;
>>> +
>> According to your DT bindings, the regulator from property "vref-supply" should
>> be used. This is missing here.
> 
> Uhm, it's right below, no?
> 
>>> +	st->reg = devm_regulator_get(&spi->dev, "vref");
>>> +	if (IS_ERR(st->reg))
>>> +		return PTR_ERR(st->reg);
>>> +
>>> +	ret = regulator_enable(st->reg);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	voltage_uv = regulator_get_voltage(st->reg);
>>> +	if (voltage_uv < 0)
>>> +		goto error_disable_reg;
>> Missing ret = voltage_uv before goto. Or just drop voltage_uv completely and use ret instead.
> 
> Fixed.
> 
>>> +	st->vref_mv = voltage_uv / 1000;
>> How hard do you want to depend on a voltage regulator? Doing regulator_get_voltage()
>> could even be called dynamically in _read_raw(), making a real regulator optional.
> 
> Hmm. I understand that the DAC voltage input may not be provided by a
> regulator, but is that a common scenario?  No other DAC driver I looked
> at handles that case, they all consider it an error if the regulator is
> absent.
Sure - if there isn't one, then a fixed regulator can be specified in the DT
to provide whatever the voltage is.
> 
>>> +
>>> +	ret = dac8554_powerdown(st, DAC8554_PWRDN_100K);
>>> +	if (ret)
>>> +		goto error_disable_reg;
>>> +
>>> +	ret = iio_device_register(indio_dev);
>>> +	if (ret)
>>> +		goto error_disable_reg;
>>> +
>>> +	return 0;
>>> +
>>> +error_disable_reg:
>>> +	regulator_disable(st->reg);
>>> +	return ret;
>>> +}
>>> +
>>> +static int dac8554_remove(struct spi_device *spi)
>>> +{
>>> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
>>> +	struct dac8554_state *st = iio_priv(indio_dev);
>>> +
>>> +	iio_device_unregister(indio_dev);
>>> +	regulator_disable(st->reg);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static const struct of_device_id dac8554_of_match[] = {
>>> +	{ .compatible = "ti,dac8554" },
>>> +	{ }
>>> +};
>>> +MODULE_DEVICE_TABLE(of, dac8554_of_match);
>>> +
>>> +static struct spi_driver dac8554_driver = {
>>> +	.driver = {
>>> +		.name = DAC8554_DRIVERNAME,
>>> +		.owner = THIS_MODULE,
>>> +		.of_match_table = dac8554_of_match,
>>> +	 },
>>> +	.probe = dac8554_probe,
>>> +	.remove = dac8554_remove,
>>> +};
>>> +module_spi_driver(dac8554_driver);
>>> +
>>> +MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>");
>>> +MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
>>> +MODULE_LICENSE("GPL v2");
> 
> Thanks for the review!
> 
> Nikolaus
> 

Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Hartmut Knaack]

Nikolaus Schulz schrieb am 12.12.2014 um 16:58:
> On Sat, Dec 06, 2014 at 12:36:19PM +0100, Hartmut Knaack wrote:
>> Nikolaus Schulz schrieb am 24.11.2014 um 20:50:
>>> The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
>>> interface.
>>>
>>> Changes in v2:
>>> * Use DMA-safe buffer for SPI transfer
>>> * Normalize powerdown_mode name "hi-z" to "three_state" as per
>>>   ABI/testing/sysfs-bus-iio
>>> * Register device late in probe function
>>> * Avoid powerdown broadcast update, which touches all DAC on the bus
>> There are a few issues left, please see my comments inline.
>>>
>>> Signed-off-by: Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
>>> ---
>>>  drivers/iio/dac/Kconfig      |  10 ++
>>>  drivers/iio/dac/Makefile     |   1 +
>>>  drivers/iio/dac/ti-dac8554.c | 374 +++++++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 385 insertions(+)
>>>  create mode 100644 drivers/iio/dac/ti-dac8554.c
> [...]
>>> diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
>>> new file mode 100644
>>> index 0000000..fca751f
>>> --- /dev/null
>>> +++ b/drivers/iio/dac/ti-dac8554.c
>>> @@ -0,0 +1,374 @@
>>> +/*
>>> + * TI DAC8554 Digital to Analog Converter SPI driver
>>> + *
>>> + * Copyright (C) 2014 Avionic Design GmbH
>>> + *
>>> + * Based on ad5446r_spi.c
>>> + * Copyright (C) 2010,2011 Analog Devices Inc.
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + */
>>> +
>>> +#include <linux/spi/spi.h>
>>> +#include <linux/regulator/consumer.h>
>>> +#include <linux/module.h>
>>> +#include <linux/iio/iio.h>
>>> +#include <linux/of.h>
>>> +
>>> +#define DAC8554_DRIVERNAME			"ti-dac8554"
>>> +#define DAC8554_DAC_CHANNELS			4
>>> +
>>> +/* Load commands */
>>> +#define DAC8554_CMD_STORE_DAC_N			0x0
>>> +#define DAC8554_CMD_UPDATE_DAC_N		0x1
>>> +#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
>>> +#define DAC8554_CMD_UPDATE_BROADCAST		0x3
>>> +
>>> +#define DAC8554_BROADCAST_USE_SRDATA		0x2
>> Add a blank line here.
> 
> Fixed.
> 
>>> +/* Powerdown modes (ORed PD1|PD2 bits) */
>> It took my some time to figure out ORed. I think you could drop it and just
>> mention (PD1 | PD2 bits).
> 
> Agreed, and fixed.
> 
>>> +#define DAC8554_PWRDN_HIZ			0x0
>>> +#define DAC8554_PWRDN_1K			0x1
>>> +#define DAC8554_PWRDN_100K			0x2
>>> +
>>> +#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
>>> +
>>> +/**
>>> + * struct dac8554_state - driver instance specific data
>>> + * @spi:		spi_device
>> SPI device?
> 
> Yes, fixed.
> 
>>> + * @reg:		supply regulator
>>> + * @addr:		two-bit chip address
>>> + * @vref_mv:		reference voltage in millivolt
>>> + * @val			DAC/channel data
>> DAC channel data?
> 
> "channel data" will do, actually.
> 
>>> + * @powerdown		channel powerdown flag
>>> + * @powerdown_mode	channel powerdown mode
>>> + * @xfer		SPI transfer buffer
>> Half of the comments are with colon, the other half are missing it.
> 
> Fixed.
> 
>>> + */
>>> +struct dac8554_state {
>>> +	struct spi_device		*spi;
>>> +	struct regulator		*reg;
>>> +	unsigned			addr;
>>> +	unsigned			vref_mv;
>>> +	u16				val[DAC8554_DAC_CHANNELS];
>>> +	bool				powerdown[DAC8554_DAC_CHANNELS];
>>> +	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
>>> +
>>> +	/*
>>> +	 * DMA (thus cache coherency maintenance) requires the
>>> +	 * transfer buffers to live in their own cache lines.
>>> +	 */
>>> +	u8				xfer[3] ____cacheline_aligned;
>>> +};
>>> +
>>> +static int dac8554_spi_write(struct dac8554_state *st,
>>> +			     unsigned cmd,
>>> +			     unsigned chan_addr,
>>> +			     unsigned val)
>>> +{
>>> +	u32 data;
>>> +
>>> +	/*
>>> +	 * The input shift register is 24 bits wide. The 8 MSB are
>>> +	 * control bits, followed by 16 data bits.
>>> +	 * The first two bits A1 and A0 address a DAC8554 chip.
>>> +	 * The next two are the command bits, LD1 and LD0.
>>> +	 * After a don't-care-bit, the next two bits select the channel.
>>> +	 * The final control bit PD0 is a flag signalling if the data
>>> +	 * bits encode a powerdown mode. We merge PD0 with the adjacent
>>> +	 * data bits.
>>> +	 */
>>> +
>>> +	if (cmd > 3 || chan_addr > 3 ||
>>> +			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
>>> +		return -EINVAL;
>>> +
>>> +	data =st->addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
>> Could be more readable by using definition for the magic shifts, or macros.
> 
> Hmm. The magic is all concentrated at this place, and the variable names
> tell the story, so I figured that's ok.  But, why not: fixed.
> 
>>> +	st->xfer[0] =ata >> 16;
>>> +	st->xfer[1] =ata >> 8;
>>> +	st->xfer[2] =ata;
>>> +
>>> +	return spi_write(st->spi, st->xfer, sizeof(st->xfer));
>>> +}
>>> +
>>> +static int dac8554_read_raw(struct iio_dev *indio_dev,
>>> +			    struct iio_chan_spec const *chan,
>>> +			    int *val,
>>> +			    int *val2,
>>> +			    long m)
>> Commonly, m is called mask (like you do in _write_raw).
> 
> Ah yes. Fixed.
> 
>>> +{
>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>> +
>>> +	switch (m) {
>>> +	case IIO_CHAN_INFO_RAW:
>>> +		*val =t->val[chan->address];
>>> +		return IIO_VAL_INT;
>>> +	case IIO_CHAN_INFO_SCALE:
>>> +		*val =t->vref_mv;
>>> +		*val2 =6;
>>> +		return IIO_VAL_FRACTIONAL_LOG2;
>>> +	}
>>> +	return -EINVAL;
>>> +}
>>> +
>>> +static int dac8554_write_raw(struct iio_dev *indio_dev,
>>> +			     struct iio_chan_spec const *chan,
>>> +			     int val,
>>> +			     int val2,
>>> +			     long mask)
>>> +{
>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>> +	int err;
>>> +
>>> +	switch (mask) {
>>> +	case IIO_CHAN_INFO_RAW:
>>> +		if (val > 0xffff || val < 0)
>>> +			return -EINVAL;
>>> +
>>> +		err =ac8554_spi_write(st, DAC8554_CMD_UPDATE_DAC_N,
>>> +					chan->address, val);
>>> +		if (err)
>>> +			return err;
>>> +
>>> +		st->val[chan->address] =al;
>>> +
>>> +		/* By hw design, DAC updates automatically trigger powerup. */
>>> +		st->powerdown[chan->address] =alse;
>>> +
>>> +		return 0;
>>> +
>>> +	default:
>>> +		return -EINVAL;
>>> +	}
>>> +}
>>> +
>>> +static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
>>> +				      const struct iio_chan_spec *chan)
>>> +{
>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>> +
>>> +	return st->powerdown_mode[chan->address];
>>> +}
>>> +
>>> +static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
>>> +				      const struct iio_chan_spec *chan,
>>> +				      unsigned int mode)
>>> +{
>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>> +
>>> +	st->powerdown_mode[chan->address] =ode;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
>>> +					  uintptr_t private,
>>> +					  const struct iio_chan_spec *chan,
>>> +					  char *buf)
>>> +{
>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>> +
>>> +	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
>>> +}
>>> +
>>> +static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
>>> +					   uintptr_t private,
>>> +					   const struct iio_chan_spec *chan,
>>> +					   const char *buf,
>>> +					   size_t len)
>>> +{
>>> +	bool powerdown;
>>> +	int ret;
>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>> +	u8 powerdown_mode;
>>> +
>>> +	ret =trtobool(buf, &powerdown);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	st->powerdown[chan->address] =owerdown;
>>> +
>>> +	if (powerdown) {
>>> +		powerdown_mode =t->powerdown_mode[chan->address];
>>> +		ret =ac8554_spi_write(st,
>>> +				DAC8554_CMD_UPDATE_DAC_N,
>>> +				chan->address,
>>> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
>> The parameters sill fit on line even with proper indentation.
> 
> Fixed.
> 
>>> +	} else {
>>> +		/* Load DAC with cached value. This triggers a powerup. */
>>> +		ret =ac8554_spi_write(st,
>>> +				DAC8554_CMD_UPDATE_DAC_N,
>>> +				chan->address,
>>> +				st->val[chan->address]);
>> Same here with indentation.
> 
> Fixed.
> 
>>> +	}
>>> +
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	return len;
>> Just: return (ret) ? ret : len;
> 
> I think avoiding the ternary operator makes the code more readable, and
> it separates the error path from normal operation. So I would prefer to
> keep it that way.
Fair enough.
> 
>>> +}
>>> +
>>> +static int dac8554_powerdown(struct dac8554_state *st,
>>> +			     u8 powerdown_mode)
>>> +{
>>> +	int chan, cmd, ret;
>>> +
>>> +	for (chan =AC8554_DAC_CHANNELS-1; chan >= 0; --chan) {
>> Please mind spaces around operators.
> 
> Fixed.
> 
>>> +		cmd =han ? DAC8554_CMD_STORE_DAC_N
>>> +			   : DAC8554_CMD_STORE_DAC_N_UPDATE_ALL;
>>> +		ret =ac8554_spi_write(st, cmd, chan,
>>> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
>>> +		if (ret)
>>> +			return ret;
>>> +	}
>>> +
>>> +	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
>>> +	memset(st->powerdown, true, sizeof(st->powerdown));
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static const struct iio_info dac8554_info =
>>> +	.write_raw = ac8554_write_raw,
>>> +	.read_raw =ac8554_read_raw,
>>> +	.driver_module =HIS_MODULE,
>>> +};
>>> +
>>> +static const char * const dac8554_powerdown_modes[] =
>>> +	"three_state",
>>> +	"1kohm_to_gnd",
>>> +	"100kohm_to_gnd"
>>> +};
>>> +
>>> +static const struct iio_enum dac8854_powerdown_mode_enum =
>>> +	.items = ac8554_powerdown_modes,
>>> +	.num_items =RRAY_SIZE(dac8554_powerdown_modes),
>>> +	.get =ac8554_get_powerdown_mode,
>>> +	.set =ac8554_set_powerdown_mode,
>>> +};
>>> +
>>> +static const struct iio_chan_spec_ext_info dac8554_ext_info[] =
>>> +	{
>>> +		.name =powerdown",
>>> +		.read =ac8554_read_dac_powerdown,
>>> +		.write =ac8554_write_dac_powerdown,
>>> +		.shared =IO_SEPARATE,
>>> +	},
>>> +	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
>>> +		 &dac8854_powerdown_mode_enum),
>>> +	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
>>> +	{ },
>>> +};
>>> +
>>> +#define DAC8554_CHANNEL(chan) { \
>>> +	.type =IO_VOLTAGE, \
>>> +	.indexed =, \
>>> +	.output =, \
>>> +	.channel =chan), \
>>> +	.info_mask_separate =IT(IIO_CHAN_INFO_RAW), \
>>> +	.info_mask_shared_by_type =IT(IIO_CHAN_INFO_SCALE), \
>>> +	.address =chan), \
>>> +	.ext_info =ac8554_ext_info, \
>>> +}
>>> +const struct iio_chan_spec dac8554_channels[] =
>>> +	DAC8554_CHANNEL(0),
>>> +	DAC8554_CHANNEL(1),
>>> +	DAC8554_CHANNEL(2),
>>> +	DAC8554_CHANNEL(3),
>>> +};
>>> +#undef DAC8554_CHANNEL
>>> +
>>> +static int dac8554_probe(struct spi_device *spi)
>>> +{
>>> +	struct dac8554_state *st;
>>> +	struct iio_dev *indio_dev;
>>> +	int ret, voltage_uv;
>>> +	u32 addr;
>>> +
>>> +	indio_dev =evm_iio_device_alloc(&spi->dev, sizeof(*st));
>>> +	if (!indio_dev)
>>> +		return -ENOMEM;
>>> +
>>> +	indio_dev->dev.parent =spi->dev;
>>> +	indio_dev->name =AC8554_DRIVERNAME;
>>> +	indio_dev->info =dac8554_info;
>>> +	indio_dev->modes =NDIO_DIRECT_MODE;
>>> +	indio_dev->channels =ac8554_channels;
>>> +	indio_dev->num_channels =RRAY_SIZE(dac8554_channels);
>>> +
>>> +	spi_set_drvdata(spi, indio_dev);
>>> +
>>> +	st =io_priv(indio_dev);
>>> +
>>> +	if (!spi->dev.of_node) {
>>> +		dev_err(&spi->dev, "missing OF node");
>>> +		return -ENODEV;
>>> +	}
>>> +	ret =f_property_read_u32(spi->dev.of_node, "address", &addr);
>>> +	if (ret || addr < 0 || addr > 2) {
>>> +		dev_err(&spi->dev, "no or invalid chip address");
>>> +		return -ENODEV;
>>> +	}
>>> +
>>> +	st->spi =pi;
>>> +	st->addr =ddr;
>>> +
>> According to your DT bindings, the regulator from property "vref-supply" should
>> be used. This is missing here.
> 
> Uhm, it's right below, no?
Looking into your DT bindings patch (which unfortunately didn't make it into our
list), you specify "vref-supply" as a required property. So, I expected that you
intended to make use of this property somewhere around here.
> 
>>> +	st->reg =evm_regulator_get(&spi->dev, "vref");
>>> +	if (IS_ERR(st->reg))
>>> +		return PTR_ERR(st->reg);
>>> +
>>> +	ret =egulator_enable(st->reg);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	voltage_uv =egulator_get_voltage(st->reg);
>>> +	if (voltage_uv < 0)
>>> +		goto error_disable_reg;
>> Missing ret =oltage_uv before goto. Or just drop voltage_uv completely and use ret instead.
> 
> Fixed.
> 
>>> +	st->vref_mv =oltage_uv / 1000;
>> How hard do you want to depend on a voltage regulator? Doing regulator_get_voltage()
>> could even be called dynamically in _read_raw(), making a real regulator optional.
> 
> Hmm. I understand that the DAC voltage input may not be provided by a
> regulator, but is that a common scenario?  No other DAC driver I looked
> at handles that case, they all consider it an error if the regulator is
> absent.
> 
I had people in mind, who might want to use such DAC with one of the popular
embedded boards like Raspberry Pi - people who would just like to "plug and
play" without the need or ability to build a kernel (or would prefer to go
with the convenience of a distribution kernel). But since you've put a
dependency on OF, I don't see a way to use this device with a stock distribution
kernel anyway.
But I still think that calculating the actual voltage during _read_raw() would
be a good idea, as there is support for regulators providing different voltages,
which can be changed during runtime.
>>> +
>>> +	ret =ac8554_powerdown(st, DAC8554_PWRDN_100K);
>>> +	if (ret)
>>> +		goto error_disable_reg;
>>> +
>>> +	ret =io_device_register(indio_dev);
>>> +	if (ret)
>>> +		goto error_disable_reg;
>>> +
>>> +	return 0;
>>> +
>>> +error_disable_reg:
>>> +	regulator_disable(st->reg);
>>> +	return ret;
>>> +}
>>> +
>>> +static int dac8554_remove(struct spi_device *spi)
>>> +{
>>> +	struct iio_dev *indio_dev =pi_get_drvdata(spi);
>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>> +
>>> +	iio_device_unregister(indio_dev);
>>> +	regulator_disable(st->reg);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static const struct of_device_id dac8554_of_match[] =
>>> +	{ .compatible = ti,dac8554" },
>>> +	{ }
>>> +};
>>> +MODULE_DEVICE_TABLE(of, dac8554_of_match);
>>> +
>>> +static struct spi_driver dac8554_driver =
>>> +	.driver = 
>>> +		.name = AC8554_DRIVERNAME,
>>> +		.owner =HIS_MODULE,
>>> +		.of_match_table =ac8554_of_match,
>>> +	 },
>>> +	.probe =ac8554_probe,
>>> +	.remove =ac8554_remove,
>>> +};
>>> +module_spi_driver(dac8554_driver);
>>> +
>>> +MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>");
>>> +MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
>>> +MODULE_LICENSE("GPL v2");
> 
> Thanks for the review!
> 
> Nikolaus
> 

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Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Hartmut Knaack]

Hartmut Knaack schrieb am 13.12.2014 um 12:18:
> Nikolaus Schulz schrieb am 12.12.2014 um 16:58:
>> On Sat, Dec 06, 2014 at 12:36:19PM +0100, Hartmut Knaack wrote:
>>> Nikolaus Schulz schrieb am 24.11.2014 um 20:50:
>>>> The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
>>>> interface.
>>>>
>>>> Changes in v2:
>>>> * Use DMA-safe buffer for SPI transfer
>>>> * Normalize powerdown_mode name "hi-z" to "three_state" as per
>>>>   ABI/testing/sysfs-bus-iio
>>>> * Register device late in probe function
>>>> * Avoid powerdown broadcast update, which touches all DAC on the bus
>>> There are a few issues left, please see my comments inline.
>>>>
>>>> Signed-off-by: Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
>>>> ---
>>>>  drivers/iio/dac/Kconfig      |  10 ++
>>>>  drivers/iio/dac/Makefile     |   1 +
>>>>  drivers/iio/dac/ti-dac8554.c | 374 +++++++++++++++++++++++++++++++++++++++++++
>>>>  3 files changed, 385 insertions(+)
>>>>  create mode 100644 drivers/iio/dac/ti-dac8554.c
>> [...]
>>>> diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
>>>> new file mode 100644
>>>> index 0000000..fca751f
>>>> --- /dev/null
>>>> +++ b/drivers/iio/dac/ti-dac8554.c
>>>> @@ -0,0 +1,374 @@
>>>> +/*
>>>> + * TI DAC8554 Digital to Analog Converter SPI driver
>>>> + *
>>>> + * Copyright (C) 2014 Avionic Design GmbH
>>>> + *
>>>> + * Based on ad5446r_spi.c
>>>> + * Copyright (C) 2010,2011 Analog Devices Inc.
>>>> + *
>>>> + * This program is free software; you can redistribute it and/or modify
>>>> + * it under the terms of the GNU General Public License version 2 as
>>>> + * published by the Free Software Foundation.
>>>> + */
>>>> +
>>>> +#include <linux/spi/spi.h>
>>>> +#include <linux/regulator/consumer.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/iio/iio.h>
>>>> +#include <linux/of.h>
>>>> +
>>>> +#define DAC8554_DRIVERNAME			"ti-dac8554"
>>>> +#define DAC8554_DAC_CHANNELS			4
>>>> +
>>>> +/* Load commands */
>>>> +#define DAC8554_CMD_STORE_DAC_N			0x0
>>>> +#define DAC8554_CMD_UPDATE_DAC_N		0x1
>>>> +#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
>>>> +#define DAC8554_CMD_UPDATE_BROADCAST		0x3
>>>> +
>>>> +#define DAC8554_BROADCAST_USE_SRDATA		0x2
>>> Add a blank line here.
>>
>> Fixed.
>>
>>>> +/* Powerdown modes (ORed PD1|PD2 bits) */
>>> It took my some time to figure out ORed. I think you could drop it and just
>>> mention (PD1 | PD2 bits).
>>
>> Agreed, and fixed.
>>
>>>> +#define DAC8554_PWRDN_HIZ			0x0
>>>> +#define DAC8554_PWRDN_1K			0x1
>>>> +#define DAC8554_PWRDN_100K			0x2
>>>> +
>>>> +#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
>>>> +
>>>> +/**
>>>> + * struct dac8554_state - driver instance specific data
>>>> + * @spi:		spi_device
>>> SPI device?
>>
>> Yes, fixed.
>>
>>>> + * @reg:		supply regulator
>>>> + * @addr:		two-bit chip address
>>>> + * @vref_mv:		reference voltage in millivolt
>>>> + * @val			DAC/channel data
>>> DAC channel data?
>>
>> "channel data" will do, actually.
>>
>>>> + * @powerdown		channel powerdown flag
>>>> + * @powerdown_mode	channel powerdown mode
>>>> + * @xfer		SPI transfer buffer
>>> Half of the comments are with colon, the other half are missing it.
>>
>> Fixed.
>>
>>>> + */
>>>> +struct dac8554_state {
>>>> +	struct spi_device		*spi;
>>>> +	struct regulator		*reg;
>>>> +	unsigned			addr;
>>>> +	unsigned			vref_mv;
>>>> +	u16				val[DAC8554_DAC_CHANNELS];
>>>> +	bool				powerdown[DAC8554_DAC_CHANNELS];
>>>> +	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
>>>> +
>>>> +	/*
>>>> +	 * DMA (thus cache coherency maintenance) requires the
>>>> +	 * transfer buffers to live in their own cache lines.
>>>> +	 */
>>>> +	u8				xfer[3] ____cacheline_aligned;
>>>> +};
>>>> +
>>>> +static int dac8554_spi_write(struct dac8554_state *st,
>>>> +			     unsigned cmd,
>>>> +			     unsigned chan_addr,
>>>> +			     unsigned val)
>>>> +{
>>>> +	u32 data;
>>>> +
>>>> +	/*
>>>> +	 * The input shift register is 24 bits wide. The 8 MSB are
>>>> +	 * control bits, followed by 16 data bits.
>>>> +	 * The first two bits A1 and A0 address a DAC8554 chip.
>>>> +	 * The next two are the command bits, LD1 and LD0.
>>>> +	 * After a don't-care-bit, the next two bits select the channel.
>>>> +	 * The final control bit PD0 is a flag signalling if the data
>>>> +	 * bits encode a powerdown mode. We merge PD0 with the adjacent
>>>> +	 * data bits.
>>>> +	 */
>>>> +
>>>> +	if (cmd > 3 || chan_addr > 3 ||
>>>> +			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
>>>> +		return -EINVAL;
>>>> +
>>>> +	data =st->addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
>>> Could be more readable by using definition for the magic shifts, or macros.
>>
>> Hmm. The magic is all concentrated at this place, and the variable names
>> tell the story, so I figured that's ok.  But, why not: fixed.
>>
>>>> +	st->xfer[0] =ata >> 16;
>>>> +	st->xfer[1] =ata >> 8;
>>>> +	st->xfer[2] =ata;
>>>> +
>>>> +	return spi_write(st->spi, st->xfer, sizeof(st->xfer));
>>>> +}
>>>> +
>>>> +static int dac8554_read_raw(struct iio_dev *indio_dev,
>>>> +			    struct iio_chan_spec const *chan,
>>>> +			    int *val,
>>>> +			    int *val2,
>>>> +			    long m)
>>> Commonly, m is called mask (like you do in _write_raw).
>>
>> Ah yes. Fixed.
>>
>>>> +{
>>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>>> +
>>>> +	switch (m) {
>>>> +	case IIO_CHAN_INFO_RAW:
>>>> +		*val =t->val[chan->address];
>>>> +		return IIO_VAL_INT;
>>>> +	case IIO_CHAN_INFO_SCALE:
>>>> +		*val =t->vref_mv;
>>>> +		*val2 =6;
>>>> +		return IIO_VAL_FRACTIONAL_LOG2;
>>>> +	}
>>>> +	return -EINVAL;
>>>> +}
>>>> +
>>>> +static int dac8554_write_raw(struct iio_dev *indio_dev,
>>>> +			     struct iio_chan_spec const *chan,
>>>> +			     int val,
>>>> +			     int val2,
>>>> +			     long mask)
>>>> +{
>>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>>> +	int err;
>>>> +
>>>> +	switch (mask) {
>>>> +	case IIO_CHAN_INFO_RAW:
>>>> +		if (val > 0xffff || val < 0)
>>>> +			return -EINVAL;
>>>> +
>>>> +		err =ac8554_spi_write(st, DAC8554_CMD_UPDATE_DAC_N,
>>>> +					chan->address, val);
>>>> +		if (err)
>>>> +			return err;
>>>> +
>>>> +		st->val[chan->address] =al;
>>>> +
>>>> +		/* By hw design, DAC updates automatically trigger powerup. */
>>>> +		st->powerdown[chan->address] =alse;
>>>> +
>>>> +		return 0;
>>>> +
>>>> +	default:
>>>> +		return -EINVAL;
>>>> +	}
>>>> +}
>>>> +
>>>> +static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
>>>> +				      const struct iio_chan_spec *chan)
>>>> +{
>>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>>> +
>>>> +	return st->powerdown_mode[chan->address];
>>>> +}
>>>> +
>>>> +static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
>>>> +				      const struct iio_chan_spec *chan,
>>>> +				      unsigned int mode)
>>>> +{
>>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>>> +
>>>> +	st->powerdown_mode[chan->address] =ode;
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
>>>> +					  uintptr_t private,
>>>> +					  const struct iio_chan_spec *chan,
>>>> +					  char *buf)
>>>> +{
>>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>>> +
>>>> +	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
>>>> +}
>>>> +
>>>> +static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
>>>> +					   uintptr_t private,
>>>> +					   const struct iio_chan_spec *chan,
>>>> +					   const char *buf,
>>>> +					   size_t len)
>>>> +{
>>>> +	bool powerdown;
>>>> +	int ret;
>>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>>> +	u8 powerdown_mode;
>>>> +
>>>> +	ret =trtobool(buf, &powerdown);
>>>> +	if (ret)
>>>> +		return ret;
>>>> +
>>>> +	st->powerdown[chan->address] =owerdown;
>>>> +
>>>> +	if (powerdown) {
>>>> +		powerdown_mode =t->powerdown_mode[chan->address];
>>>> +		ret =ac8554_spi_write(st,
>>>> +				DAC8554_CMD_UPDATE_DAC_N,
>>>> +				chan->address,
>>>> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
>>> The parameters sill fit on line even with proper indentation.
>>
>> Fixed.
>>
>>>> +	} else {
>>>> +		/* Load DAC with cached value. This triggers a powerup. */
>>>> +		ret =ac8554_spi_write(st,
>>>> +				DAC8554_CMD_UPDATE_DAC_N,
>>>> +				chan->address,
>>>> +				st->val[chan->address]);
>>> Same here with indentation.
>>
>> Fixed.
>>
>>>> +	}
>>>> +
>>>> +	if (ret)
>>>> +		return ret;
>>>> +
>>>> +	return len;
>>> Just: return (ret) ? ret : len;
>>
>> I think avoiding the ternary operator makes the code more readable, and
>> it separates the error path from normal operation. So I would prefer to
>> keep it that way.
> Fair enough.
>>
>>>> +}
>>>> +
>>>> +static int dac8554_powerdown(struct dac8554_state *st,
>>>> +			     u8 powerdown_mode)
>>>> +{
>>>> +	int chan, cmd, ret;
>>>> +
>>>> +	for (chan =AC8554_DAC_CHANNELS-1; chan >= 0; --chan) {
>>> Please mind spaces around operators.
>>
>> Fixed.
>>
>>>> +		cmd =han ? DAC8554_CMD_STORE_DAC_N
>>>> +			   : DAC8554_CMD_STORE_DAC_N_UPDATE_ALL;
>>>> +		ret =ac8554_spi_write(st, cmd, chan,
>>>> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
>>>> +		if (ret)
>>>> +			return ret;
>>>> +	}
>>>> +
>>>> +	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
>>>> +	memset(st->powerdown, true, sizeof(st->powerdown));
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static const struct iio_info dac8554_info =
>>>> +	.write_raw = ac8554_write_raw,
>>>> +	.read_raw =ac8554_read_raw,
>>>> +	.driver_module =HIS_MODULE,
>>>> +};
>>>> +
>>>> +static const char * const dac8554_powerdown_modes[] =
>>>> +	"three_state",
>>>> +	"1kohm_to_gnd",
>>>> +	"100kohm_to_gnd"
>>>> +};
>>>> +
>>>> +static const struct iio_enum dac8854_powerdown_mode_enum =
>>>> +	.items = ac8554_powerdown_modes,
>>>> +	.num_items =RRAY_SIZE(dac8554_powerdown_modes),
>>>> +	.get =ac8554_get_powerdown_mode,
>>>> +	.set =ac8554_set_powerdown_mode,
>>>> +};
>>>> +
>>>> +static const struct iio_chan_spec_ext_info dac8554_ext_info[] =
>>>> +	{
>>>> +		.name =powerdown",
>>>> +		.read =ac8554_read_dac_powerdown,
>>>> +		.write =ac8554_write_dac_powerdown,
>>>> +		.shared =IO_SEPARATE,
>>>> +	},
>>>> +	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
>>>> +		 &dac8854_powerdown_mode_enum),
>>>> +	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
>>>> +	{ },
>>>> +};
>>>> +
>>>> +#define DAC8554_CHANNEL(chan) { \
>>>> +	.type =IO_VOLTAGE, \
>>>> +	.indexed =, \
>>>> +	.output =, \
>>>> +	.channel =chan), \
>>>> +	.info_mask_separate =IT(IIO_CHAN_INFO_RAW), \
>>>> +	.info_mask_shared_by_type =IT(IIO_CHAN_INFO_SCALE), \
>>>> +	.address =chan), \
>>>> +	.ext_info =ac8554_ext_info, \
>>>> +}
>>>> +const struct iio_chan_spec dac8554_channels[] =
>>>> +	DAC8554_CHANNEL(0),
>>>> +	DAC8554_CHANNEL(1),
>>>> +	DAC8554_CHANNEL(2),
>>>> +	DAC8554_CHANNEL(3),
>>>> +};
>>>> +#undef DAC8554_CHANNEL
>>>> +
>>>> +static int dac8554_probe(struct spi_device *spi)
>>>> +{
>>>> +	struct dac8554_state *st;
>>>> +	struct iio_dev *indio_dev;
>>>> +	int ret, voltage_uv;
>>>> +	u32 addr;
>>>> +
>>>> +	indio_dev =evm_iio_device_alloc(&spi->dev, sizeof(*st));
>>>> +	if (!indio_dev)
>>>> +		return -ENOMEM;
>>>> +
>>>> +	indio_dev->dev.parent =spi->dev;
>>>> +	indio_dev->name =AC8554_DRIVERNAME;
>>>> +	indio_dev->info =dac8554_info;
>>>> +	indio_dev->modes =NDIO_DIRECT_MODE;
>>>> +	indio_dev->channels =ac8554_channels;
>>>> +	indio_dev->num_channels =RRAY_SIZE(dac8554_channels);
>>>> +
>>>> +	spi_set_drvdata(spi, indio_dev);
>>>> +
>>>> +	st =io_priv(indio_dev);
>>>> +
>>>> +	if (!spi->dev.of_node) {
>>>> +		dev_err(&spi->dev, "missing OF node");
>>>> +		return -ENODEV;
>>>> +	}
>>>> +	ret =f_property_read_u32(spi->dev.of_node, "address", &addr);
>>>> +	if (ret || addr < 0 || addr > 2) {
>>>> +		dev_err(&spi->dev, "no or invalid chip address");
>>>> +		return -ENODEV;
>>>> +	}
>>>> +
>>>> +	st->spi =pi;
>>>> +	st->addr =ddr;
>>>> +
>>> According to your DT bindings, the regulator from property "vref-supply" should
>>> be used. This is missing here.
>>
>> Uhm, it's right below, no?
> Looking into your DT bindings patch (which unfortunately didn't make it into our
> list), you specify "vref-supply" as a required property. So, I expected that you
> intended to make use of this property somewhere around here.
>>
>>>> +	st->reg =evm_regulator_get(&spi->dev, "vref");
>>>> +	if (IS_ERR(st->reg))
>>>> +		return PTR_ERR(st->reg);
>>>> +
>>>> +	ret =egulator_enable(st->reg);
>>>> +	if (ret)
>>>> +		return ret;
>>>> +
>>>> +	voltage_uv =egulator_get_voltage(st->reg);
>>>> +	if (voltage_uv < 0)
>>>> +		goto error_disable_reg;
>>> Missing ret =oltage_uv before goto. Or just drop voltage_uv completely and use ret instead.
>>
>> Fixed.
>>
>>>> +	st->vref_mv =oltage_uv / 1000;
>>> How hard do you want to depend on a voltage regulator? Doing regulator_get_voltage()
>>> could even be called dynamically in _read_raw(), making a real regulator optional.
>>
>> Hmm. I understand that the DAC voltage input may not be provided by a
>> regulator, but is that a common scenario?  No other DAC driver I looked
>> at handles that case, they all consider it an error if the regulator is
>> absent.
>>
> I had people in mind, who might want to use such DAC with one of the popular
> embedded boards like Raspberry Pi - people who would just like to "plug and
> play" without the need or ability to build a kernel (or would prefer to go
> with the convenience of a distribution kernel). But since you've put a
> dependency on OF, I don't see a way to use this device with a stock distribution
> kernel anyway.
> But I still think that calculating the actual voltage during _read_raw() would
> be a good idea, as there is support for regulators providing different voltages,
> which can be changed during runtime.
One more thing: you should consider to add a dependency on regulators in Kconfig.

>>>> +
>>>> +	ret =ac8554_powerdown(st, DAC8554_PWRDN_100K);
>>>> +	if (ret)
>>>> +		goto error_disable_reg;
>>>> +
>>>> +	ret =io_device_register(indio_dev);
>>>> +	if (ret)
>>>> +		goto error_disable_reg;
>>>> +
>>>> +	return 0;
>>>> +
>>>> +error_disable_reg:
>>>> +	regulator_disable(st->reg);
>>>> +	return ret;
>>>> +}
>>>> +
>>>> +static int dac8554_remove(struct spi_device *spi)
>>>> +{
>>>> +	struct iio_dev *indio_dev =pi_get_drvdata(spi);
>>>> +	struct dac8554_state *st =io_priv(indio_dev);
>>>> +
>>>> +	iio_device_unregister(indio_dev);
>>>> +	regulator_disable(st->reg);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static const struct of_device_id dac8554_of_match[] =
>>>> +	{ .compatible = ti,dac8554" },
>>>> +	{ }
>>>> +};
>>>> +MODULE_DEVICE_TABLE(of, dac8554_of_match);
>>>> +
>>>> +static struct spi_driver dac8554_driver =
>>>> +	.driver = 
>>>> +		.name = AC8554_DRIVERNAME,
>>>> +		.owner =HIS_MODULE,
>>>> +		.of_match_table =ac8554_of_match,
>>>> +	 },
>>>> +	.probe =ac8554_probe,
>>>> +	.remove =ac8554_remove,
>>>> +};
>>>> +module_spi_driver(dac8554_driver);
>>>> +
>>>> +MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>");
>>>> +MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
>>>> +MODULE_LICENSE("GPL v2");
>>
>> Thanks for the review!
>>
>> Nikolaus
>>
> 
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> 

Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Lars-Peter Clausen]

On 12/13/2014 12:18 PM, Hartmut Knaack wrote:
[...]
>>> According to your DT bindings, the regulator from property "vref-supply" should
>>> be used. This is missing here.
>>
>> Uhm, it's right below, no?
> Looking into your DT bindings patch (which unfortunately didn't make it into our
> list), you specify "vref-supply" as a required property. So, I expected that you
> intended to make use of this property somewhere around here.

The regulator framework takes care of this. If you request a regulator with 
$name the framework will look for a property with the name $name-supply.

>>
>>>> +	st->reg =evm_regulator_get(&spi->dev, "vref");
>>>> +	if (IS_ERR(st->reg))
>>>> +		return PTR_ERR(st->reg);
[...]

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Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Lars-Peter Clausen]

On 11/24/2014 08:50 PM, Nikolaus Schulz wrote:
[...]
> +const struct iio_chan_spec dac8554_channels[] = {

static

[...]
> +	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);

This should probably have vendor prefix.

> +	if (ret || addr < 0 || addr > 2) {
> +		dev_err(&spi->dev, "no or invalid chip address");
> +		return -ENODEV;
> +	}

Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Lars-Peter Clausen]

On 12/06/2014 12:36 PM, Hartmut Knaack wrote:
[...]
>> +static int dac8554_read_raw(struct iio_dev *indio_dev,
>> +			    struct iio_chan_spec const *chan,
>> +			    int *val,
>> +			    int *val2,
>> +			    long m)
> Commonly, m is called mask (like you do in _write_raw).

We should call it info in new driver. It used to be a mask, but that was a 
long long time ago.

[...]
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Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Nikolaus Schulz]

On Sat, Dec 13, 2014 at 12:18:50PM +0100, Hartmut Knaack wrote:
> Nikolaus Schulz schrieb am 12.12.2014 um 16:58:
> > On Sat, Dec 06, 2014 at 12:36:19PM +0100, Hartmut Knaack wrote:
> >> Nikolaus Schulz schrieb am 24.11.2014 um 20:50:
> >>> The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
> >>> interface.
[dac8554_probe:]
> >>> +	st->vref_mv =oltage_uv / 1000;
> >> How hard do you want to depend on a voltage regulator? Doing regulator_get_voltage()
> >> could even be called dynamically in _read_raw(), making a real regulator optional.
> > 
> > Hmm. I understand that the DAC voltage input may not be provided by a
> > regulator, but is that a common scenario?  No other DAC driver I looked
> > at handles that case, they all consider it an error if the regulator is
> > absent.
> > 
> I had people in mind, who might want to use such DAC with one of the popular
> embedded boards like Raspberry Pi - people who would just like to "plug and
> play" without the need or ability to build a kernel (or would prefer to go
> with the convenience of a distribution kernel). But since you've put a
> dependency on OF, I don't see a way to use this device with a stock distribution
> kernel anyway.

As long as the kernel supports devicetree, compiling the module and a
new DT blob should be enough to enable support for the DAC8554.

And, as Jonathan has pointed out, if there is no real regulator
providing the input current, a fixed regulator can be added to the DT.

> But I still think that calculating the actual voltage during _read_raw() would
> be a good idea, as there is support for regulators providing different voltages,
> which can be changed during runtime.

Agreed.

-- 
Avionic Design GmbH
Nikolaus Schulz
Wragekamp 10
D-22397 Hamburg
Germany

Tel.:  +49 40 88187-163
Fax:   +49 40 88187-150
Email: nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org

Avionic Design GmbH
Amtsgericht Hamburg HRB 82598
Geschäftsführung: Cornelis Broers
Ust.-Ident-Nr.: DE813378254

Re: [PATCH v2 2/2] iio: add driver for the TI DAC8554

[Nikolaus Schulz]

On Sat, Dec 13, 2014 at 12:29:57PM +0100, Lars-Peter Clausen wrote:
> On 11/24/2014 08:50 PM, Nikolaus Schulz wrote:
> [...]
> >+const struct iio_chan_spec dac8554_channels[] = {
> 
> static
> 
> [...]
> >+	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
> 
> This should probably have vendor prefix.

Both fixed in v3, thanks!

-- 
Avionic Design GmbH
Nikolaus Schulz
Wragekamp 10
D-22397 Hamburg
Germany

Tel.:  +49 40 88187-163
Fax:   +49 40 88187-150
Email: nikolaus.schulz-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org

Avionic Design GmbH
Amtsgericht Hamburg HRB 82598
Geschäftsführung: Cornelis Broers
Ust.-Ident-Nr.: DE813378254