Re: [PATCH] iio: dac: mcp4902/mcp4912/mcp4922 dac driver

[Michael Welling <mwelling@ieee.org>]

On Wed, Jun 04, 2014 at 11:45:40AM +0200, Peter Meerwald wrote:
> 
> > This patch provides an iio device driver for the Microchip
> > MCP49x2 series DACs.
> 
> comments inline
I appologize for submitting this patch in such a poor state.

Looking at it today I noticed compilation errors and fixed them.
The changes recommended were implemented as well.

I will craft a new version of the driver and submit the patch for
review as soon as it is ready.

>  
> > Signed-off-by: Michael Welling <mwelling@ieee.org>
> > ---
> >  drivers/iio/dac/Kconfig   |   10 +++
> >  drivers/iio/dac/Makefile  |    1 +
> >  drivers/iio/dac/mcp49x2.c |  215 +++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 226 insertions(+)
> >  create mode 100644 drivers/iio/dac/mcp49x2.c
> > 
> > diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> > index f378ca8..032d678 100644
> > --- a/drivers/iio/dac/Kconfig
> > +++ b/drivers/iio/dac/Kconfig
> > @@ -163,4 +163,14 @@ config MCP4725
> >  	  To compile this driver as a module, choose M here: the module
> >  	  will be called mcp4725.
> >  
> > +config MCP49X2
> > +	tristate "MCP4902, MCP4912, MCP4922 DAC driver"
> > +	depends on SPI
> > +	---help---
> > +	  Say yes here to build the driver for the Microchip MCP49x2
> > +	  series DAC devices.
> > +
> > +	  To compile this driver as a module, choose M here: the module
> > +	  will be called mcp49x2.
> > +
> >  endmenu
> > diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> > index bb84ad6..2fdfc2e 100644
> > --- a/drivers/iio/dac/Makefile
> > +++ b/drivers/iio/dac/Makefile
> > @@ -18,3 +18,4 @@ obj-$(CONFIG_AD5686) += ad5686.o
> >  obj-$(CONFIG_AD7303) += ad7303.o
> >  obj-$(CONFIG_MAX517) += max517.o
> >  obj-$(CONFIG_MCP4725) += mcp4725.o
> > +obj-$(CONFIG_MCP49X2) += mcp49x2.o
> > diff --git a/drivers/iio/dac/mcp49x2.c b/drivers/iio/dac/mcp49x2.c
> > new file mode 100644
> > index 0000000..0375046
> > --- /dev/null
> > +++ b/drivers/iio/dac/mcp49x2.c
> > @@ -0,0 +1,215 @@
> > +/*
> > + * mcp49x2.c
> > + *
> > + * Driver for Microchip Digital to Analog Converters.
> > + * Supports MCP4902, MCP4912, and MCP4922.
> > + *
> > + * Copyright (c) 2014 EMAC Inc.
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation; either version 2 of the License, or
> > + * (at your option) any later version.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/init.h>
> > +#include <linux/spi/spi.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/iio/sysfs.h>
> > +#include <linux/regulator/consumer.h>
> > +
> > +#define	MCP49X2_RES_MASK(x)		((1 << (x)) - 1)
> 
> use GENMASK() in linux/bitops.h
> 
> > +
> > +enum mcp49x2_supported_device_ids {
> > +	ID_MCP4902,
> > +	ID_MCP4912,
> > +	ID_MCP4922,
> > +};
> > +
> > +struct mcp49x2_state {
> > +	struct spi_device *spi;
> > +	unsigned int value[2];
> > +	unsigned int power_mode[2];
> > +	unsigned int vref_mv;
> > +	struct regulator *vref_reg;
> > +};
> > +
> > +#define MCP49X2_CHAN(chan, bits) {			\
> > +	.type = IIO_VOLTAGE,				\
> > +	.output = 1,					\
> > +	.indexed = 1,					\
> > +	.channel = chan,				\
> > +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
> > +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> > +	.address = chan,				\
> 
> could use .channel instead of .address
> 
> > +	.scan_type = IIO_ST('u', bits, 16, 12-(bits)),	\
> 
> consistently put macro arguments in () or don't
> 
> > +	.ext_info = NULL,				\
> 
> no need to set ext_info
> 
> > +}
> > +
> > +static int mcp49x2_spi_write(struct spi_device *spi, u8 addr, u32 val)
> > +{
> > +	u8 mosi[2];
> > +
> > +	mosi[1] = val & 0xff;
> > +	mosi[0] = (addr == 0) ? 0x00 : 0x80;
> > +	mosi[0] |= 0x30 | ((val >> 8) & 0x0f);
> > +
> > +	return spi_write(spi, mosi, 2);
> 
> SPI buffers need to be cacheline aligned?
> 
> > +}
> > +
> > +static int mcp49x2_read_raw(struct iio_dev *indio_dev,
> > +		struct iio_chan_spec const *chan,
> > +		int *val,
> > +		int *val2,
> > +		long mask)
> > +{
> > +	struct mcp49x2_state *state = iio_priv(indio_dev);
> > +
> > +	if (chan->address >= 2)
> > +		return -EINVAL;
> 
> no need to check the address; you are relying on chan being valid anyway
> 
> > +
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		*val = state->value[chan->address];
> > +		return IIO_VAL_INT;
> > +	case IIO_CHAN_INFO_SCALE:
> > +		*val = state->vref_mv;
> > +		*val2 = chan->scan_type.realbits;
> > +		return IIO_VAL_FRACTIONAL_LOG2;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> > +static int mcp49x2_write_raw(struct iio_dev *indio_dev,
> > +		struct iio_chan_spec const *chan,
> > +		int val,
> > +		int val2,
> > +		long mask)
> > +{
> > +	struct mcp49x2_state *state = iio_priv(indio_dev);
> > +
> > +	if (chan->address >= 2)
> > +		return -EINVAL;
> > +
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_RAW:
> 
> maybe check the range of val and report EINVAL if out of range?
> this silently makes val fit, no matter what
> 
> > +		val &= MCP49X2_RES_MASK(chan->scan_type.realbits);
> > +		val <<= chan->scan_type.shift;
> > +		state->value[chan->address] = val;
> > +		return mcp49x2_spi_write(state->spi, chan->address, val);
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> > +static const struct iio_chan_spec mcp49x2_channels[3][2] = {
> > +	[ID_MCP4902] = { MCP49X2_CHAN(0, 8),	MCP49X2_CHAN(1, 8) },
> > +	[ID_MCP4912] = { MCP49X2_CHAN(0, 10),	MCP49X2_CHAN(1, 10) },
> > +	[ID_MCP4922] = { MCP49X2_CHAN(0, 12),	MCP49X2_CHAN(1, 12) },
> > +};
> > +
> > +static const struct iio_info mcp49x2_info = {
> > +	.read_raw = &mcp49x2_read_raw,
> > +	.write_raw = &mcp49x2_write_raw,
> > +	.driver_module = THIS_MODULE,
> > +};
> > +
> > +static int mcp49x2_probe(struct spi_device *spi)
> > +{
> > +	struct iio_dev *indio_dev;
> > +	struct mcp49x2_state *state;
> > +	const struct spi_device_id *id;
> > +	int ret;
> > +
> > +	indio_dev = iio_device_alloc(sizeof(*state));
> 
> devm_iio_device_alloc()
> 
> > +	if (indio_dev == NULL)
> > +		return -ENOMEM;
> > +
> > +	state = iio_priv(indio_dev);
> > +	state->spi = spi;
> > +
> > +	state->vref_reg = devm_regulator_get(spi->dev, "vref");
> > +	if (!IS_ERR(state->vref_reg)) {
> > +		ret = regulator_enable(state->vref_reg);
> > +		if (ret) {
> > +			dev_err(dev, "Failed to enable vref regulator: %d\n",
> > +				ret);
> > +			goto error_free;
> > +		}
> > +
> > +		ret = regulator_get_voltage(state->vref_reg);
> > +		if (ret < 0)
> > +			goto error_disable_reg;
> > +
> > +		state->vref_mv = ret / 1000;
> > +	} else {
> > +		dev_info(dev, "Vref regulator not specified assuming 2.5V\n");
> > +		state->vref_mv = 2500;
> > +	}
> > +
> > +	spi_set_drvdata(spi, indio_dev);
> > +	id = spi_get_device_id(spi);
> > +	indio_dev->dev.parent = &spi->dev;
> > +	indio_dev->info = &mcp49x2_info;
> > +	indio_dev->modes = INDIO_DIRECT_MODE;
> > +	indio_dev->channels = mcp49x2_channels[id->driver_data];
> > +	indio_dev->num_channels = 2;
> 
> maybe use a constant for the number of channels here and also
> when declaring mcp49x2_channels[3][2]
> 
> > +	indio_dev->name = id->name;
> > +
> > +	ret = iio_device_register(indio_dev);
> 
> use devm_iio_device_register()
> drop newline
> > +
> > +	if (ret) {
> > +		dev_err(dev, "Failed to register iio device: %d\n",
> > +			ret);
> > +		goto error_disable_reg;
> > +	}
> > +
> > +	return 0;
> > +
> > +error_disable_reg:
> > +	if (!IS_ERR(state->vref_reg))
> > +		regulator_disable(state->vref_reg);
> > +error_free:
> > +	iio_device_free(indio_dev);
> > +
> > +	return ret;
> > +}
> > +
> > +static int mcp49x2_remove(struct spi_device *spi)
> > +{
> > +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> > +
> 
> iio_device_unregister()?
> but should go away with devm_ stuff
> 
> > +	iio_device_free(indio_dev);
> > +	return 0;
> > +}
> > +
> > +static const struct spi_device_id mcp49x2_id[] = {
> > +	{"mcp4902", ID_MCP4902},
> > +	{"mcp4912", ID_MCP4912},
> > +	{"mcp4922", ID_MCP4922},
> > +	{}
> > +};
> > +MODULE_DEVICE_TABLE(spi, mcp49x2_id);
> > +
> > +static struct spi_driver mcp49x2_driver = {
> > +	.driver = {
> > +		   .name = "mcp49x2",
> > +		   .owner = THIS_MODULE,
> > +		   },
> > +	.probe = mcp49x2_probe,
> > +	.remove = mcp49x2_remove,
> > +	.id_table = mcp49x2_id,
> > +};
> > +module_spi_driver(mcp49x2_driver);
> > +
> > +MODULE_AUTHOR("Michael Welling <mwelling@ieee.org>");
> > +MODULE_DESCRIPTION("Microchip MCP4902, MCP4912, MCP4922 DAC");
> > +MODULE_LICENSE("GPL v2");
> > 
> 
> -- 
> 
> Peter Meerwald
> +43-664-2444418 (mobile)