Re: Linux driver for MAX517/518/519

[Roland Stigge <stigge@antcom.de>]

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Hi,

On 03/01/11 23:28, Greg KH wrote:
>> I've written a driver for the Maxim MAX517/MAX518/MAX519 1/2-channel
>> DAC. See also the branch "max51x" of repository linux-2.6 at
>> git.antcom.de (alternatively the patch at
>> http://www.rolandstigge.de/dp/download/patches/max51x.patch).
>>
>> It's currently located in drivers/misc/max51x.c, implemented similarly
>> to the other drivers like e.g. ti_dac7512.c. The hwmon maintainer
>> pointed me to drivers/staging/iio/.
>>
>> Is it advisible now to port the driver to drivers/staging/iio or keep it
>> in drivers/misc? Where should I forward the code/patch for Linux
>> integration?
> 
> It's best to convert to the iio subsystem, as that is the way to go in
> the future.
> 
> As for where to send patches for it, send them here, and cc: the iio
> developers and me and we will be glad to comment on them and apply them
> to the kernel tree for submission to Linus's tree.

OK, done. Attaching the patch. (Also available at the above mentioned
git repository for merging.)

Thanks in advance,

Roland


BTW: Maybe we should also call it "Analog to digital converters" instead
of "Analog to digital convertors", see drivers/staging/iio/adc/Kconfig

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Added max51x iio driver

Signed-off-by: Roland Stigge <stigge@antcom.de>

diff --git a/drivers/staging/iio/Documentation/dac/max51x b/drivers/staging/iio/Documentation/dac/max51x
new file mode 100644
index 0000000..cf61a25
--- /dev/null
+++ b/drivers/staging/iio/Documentation/dac/max51x
@@ -0,0 +1,38 @@
+Kernel driver max51x
+====================
+
+Supported chips:
+  * Maxim MAX517, MAX518, MAX519
+    Prefix: 'max51x'
+    Datasheet: Publicly available at the Maxim website
+               http://www.maxim-ic.com/
+
+Author:
+        Roland Stigge <stigge@antcom.de>
+
+Description
+-----------
+
+The Maxim MAX51x is an 8-bit DAC on the I2C bus. The following table shows the
+different feature sets of the variants MAX517, MAX518 and MAX519:
+
+Feature                              MAX517 MAX518 MAX519
+--------------------------------------------------------------------------
+One output channel                   X
+Two output channels                         X      X
+Simultaneous output updates                 X      X
+Supply voltage as reference                 X
+Separate reference input             X
+Reference input for each DAC                       X
+
+Via the iio sysfs interface, there are three attributes available: value_1,
+value_2 and value_both. With value_1 and value_2, the current output values of
+the DACs can be read back from the driver and written to the device. value_both
+can be used to set both output channel values simultaneously.
+
+With MAX517, only value_1 is available.
+
+When the operating system goes to a power down state, the Power Down function
+of the chip is activated, reducing the supply current to 4uA.
+
+On power-up, the device is in 0V-output state.
diff --git a/drivers/staging/iio/Kconfig b/drivers/staging/iio/Kconfig
index ed48815..6fc35ad 100644
--- a/drivers/staging/iio/Kconfig
+++ b/drivers/staging/iio/Kconfig
@@ -42,6 +42,7 @@ config IIO_TRIGGER
 
 source "drivers/staging/iio/accel/Kconfig"
 source "drivers/staging/iio/adc/Kconfig"
+source "drivers/staging/iio/dac/Kconfig"
 source "drivers/staging/iio/gyro/Kconfig"
 source "drivers/staging/iio/imu/Kconfig"
 source "drivers/staging/iio/light/Kconfig"
diff --git a/drivers/staging/iio/Makefile b/drivers/staging/iio/Makefile
index e909674..8766e07 100644
--- a/drivers/staging/iio/Makefile
+++ b/drivers/staging/iio/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_IIO_SW_RING) += ring_sw.o
 
 obj-y += accel/
 obj-y += adc/
+obj-y += dac/
 obj-y += gyro/
 obj-y += imu/
 obj-y += light/
diff --git a/drivers/staging/iio/dac/Kconfig b/drivers/staging/iio/dac/Kconfig
new file mode 100644
index 0000000..f2c9c84
--- /dev/null
+++ b/drivers/staging/iio/dac/Kconfig
@@ -0,0 +1,14 @@
+#
+# DAC drivers
+#
+comment "Digital to analog converters"
+
+config MAX51X
+	tristate "Maxim MAX51X DAC driver"
+	depends on I2C && EXPERIMENTAL
+	help
+	  If you say yes here you get support for the Maxim chips MAX517,
+	  MAX518 and MAX519 (I2C 8-Bit DACs with rail-to-rail outputs).
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called max51x.
diff --git a/drivers/staging/iio/dac/Makefile b/drivers/staging/iio/dac/Makefile
new file mode 100644
index 0000000..3caa871
--- /dev/null
+++ b/drivers/staging/iio/dac/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for industrial I/O DAC drivers
+#
+
+obj-$(CONFIG_MAX51X) += max51x.o
diff --git a/drivers/staging/iio/dac/max51x.c b/drivers/staging/iio/dac/max51x.c
new file mode 100644
index 0000000..6d05428
--- /dev/null
+++ b/drivers/staging/iio/dac/max51x.c
@@ -0,0 +1,258 @@
+/*
+ *  max51x.c - Support for Maxim MAX517, MAX518 and MAX519
+ *
+ *  Copyright (C) 2010 Roland Stigge <stigge@antcom.de>
+ *
+ *  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.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/jiffies.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+
+#include "../iio.h"
+
+#define MAX51X_DRV_NAME	"max51x"
+
+/* Commands */
+#define COMMAND_CHANNEL0	0x00
+#define COMMAND_CHANNEL1	0x01 /* for MAX518 and MAX519 */
+#define COMMAND_PD		0x08 /* Power Down */
+
+struct max51x_data {
+	u8			values[2];
+	struct iio_dev		*indio_dev;
+};
+
+/*
+ * channel: bit 0: channel 1
+ *          bit 1: channel 2
+ * (this way, it's possible to set both channels at once)
+ */
+static ssize_t max51x_set_value(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count, int channel)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct max51x_data *data = i2c_get_clientdata(client);
+	u8 outbuf[4]; /* 1x or 2x command + value */
+	int outbuf_size = 0;
+	int res;
+	long val;
+
+	res = strict_strtol(buf, 10, &val);
+
+	if (res)
+		return res;
+
+	if (val < 0 || val > 255)
+		return -EINVAL;
+
+	if (channel & 1) {
+		data->values[0] = val;
+		outbuf[outbuf_size++] = COMMAND_CHANNEL0;
+		outbuf[outbuf_size++] = val;
+	}
+	if (channel & 2) {
+		data->values[1] = val;
+		outbuf[outbuf_size++] = COMMAND_CHANNEL1;
+		outbuf[outbuf_size++] = val;
+	}
+
+	/*
+	 * at this point, there are always 1 or 2 two-byte commands in
+	 * outbuf
+	 */
+	i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+			I2C_SMBUS_WRITE, outbuf[0], outbuf_size - 1,
+			(union i2c_smbus_data *) &outbuf[1]);
+	return count;
+}
+
+static ssize_t max51x_set_value_1(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	return max51x_set_value(dev, attr, buf, count, 1);
+}
+
+static ssize_t max51x_set_value_2(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	return max51x_set_value(dev, attr, buf, count, 2);
+}
+
+static ssize_t max51x_set_value_both(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	return max51x_set_value(dev, attr, buf, count, 3);
+}
+
+static ssize_t max51x_get_value(struct device *dev, struct device_attribute *da,
+				char *buf, int channel)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct max51x_data *data = i2c_get_clientdata(client);
+	u8 val;
+
+	if (channel == 1) {
+		val = data->values[0];
+	} else { /* channel == 2 */
+		val = data->values[1];
+	}
+
+	return sprintf(buf, "%d\n", val);
+}
+
+static ssize_t max51x_get_value_1(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	return max51x_get_value(dev, da, buf, 1);
+}
+
+static ssize_t max51x_get_value_2(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	return max51x_get_value(dev, da, buf, 2);
+}
+
+static IIO_DEVICE_ATTR(value_1, S_IWUSR | S_IRUGO,
+		max51x_get_value_1, max51x_set_value_1, 0);
+static IIO_DEVICE_ATTR(value_2, S_IWUSR | S_IRUGO,
+		max51x_get_value_2, max51x_set_value_2, 1);
+static IIO_DEVICE_ATTR(value_both, S_IWUSR, NULL, max51x_set_value_both, -1);
+
+static struct attribute *max51x_attributes[] = {
+	&iio_dev_attr_value_1.dev_attr.attr,
+	&iio_dev_attr_value_2.dev_attr.attr,
+	&iio_dev_attr_value_both.dev_attr.attr,
+	NULL
+};
+
+static struct attribute *max517_attributes[] = {
+	&iio_dev_attr_value_1.dev_attr.attr,
+	NULL
+};
+
+static struct attribute_group max51x_attribute_group = {
+	.attrs = max51x_attributes,
+};
+
+static int max51x_suspend(struct i2c_client *client, pm_message_t mesg)
+{
+	return i2c_smbus_write_byte(client, COMMAND_PD);
+}
+
+static int max51x_resume(struct i2c_client *client)
+{
+	return i2c_smbus_write_byte(client, 0);
+}
+
+static int max51x_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct max51x_data *data;
+	int err;
+
+	data = kzalloc(sizeof(struct max51x_data), GFP_KERNEL);
+	if (!data) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	i2c_set_clientdata(client, data);
+
+	/* reduced attribute set for max517 */
+	if (!strcmp(id->name, "max517"))
+		max51x_attribute_group.attrs = max517_attributes;
+
+	data->indio_dev = iio_allocate_device();
+	if (data->indio_dev == NULL) {
+		err = -ENOMEM;
+		goto exit_free_data;
+	}
+
+	/* establish that the iio_dev is a child of the i2c device */
+	data->indio_dev->dev.parent = &client->dev;
+	data->indio_dev->attrs = &max51x_attribute_group;
+	data->indio_dev->dev_data = (void *)(data);
+	data->indio_dev->driver_module = THIS_MODULE;
+	data->indio_dev->modes = INDIO_DIRECT_MODE;
+
+	err = iio_device_register(data->indio_dev);
+	if (err)
+		goto exit_free_device;
+
+	dev_info(&client->dev, "DAC registered\n");
+
+	return 0;
+
+exit_free_device:
+	iio_free_device(data->indio_dev);
+exit_free_data:
+	kfree(data);
+exit:
+	return err;
+}
+
+static int max51x_remove(struct i2c_client *client)
+{
+	struct max51x_data *data = i2c_get_clientdata(client);
+
+	kfree(data);
+
+	return 0;
+}
+
+static const struct i2c_device_id max51x_id[] = {
+	{ "max517", 0 },
+	{ "max518", 0 },
+	{ "max519", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max51x_id);
+
+static struct i2c_driver max51x_driver = {
+	.driver = {
+		.name	= MAX51X_DRV_NAME,
+	},
+	.probe		= max51x_probe,
+	.remove		= max51x_remove,
+	.suspend	= max51x_suspend,
+	.resume		= max51x_resume,
+	.id_table	= max51x_id,
+};
+
+static int __init max51x_init(void)
+{
+	return i2c_add_driver(&max51x_driver);
+}
+
+static void __exit max51x_exit(void)
+{
+	i2c_del_driver(&max51x_driver);
+}
+
+MODULE_AUTHOR("Roland Stigge <stigge@antcom.de>");
+MODULE_DESCRIPTION("MAX51X 8-bit DAC");
+MODULE_LICENSE("GPL");
+
+module_init(max51x_init);
+module_exit(max51x_exit);