[PATCH] iio: Add IIO support for the DAC on the Apex Embedded Systems STX104

[PATCH] iio: Add IIO support for the DAC on the Apex Embedded Systems STX104

[William Breathitt Gray]

The Apex Embedded Systems STX104 is a 16-channel 16-bit analog input and
2-channel 16-bit analog output PC/104 card. The STX104 incorporates a
large one mega-sample FIFO.

This driver provides IIO support for the 2-channel DAC on the STX104.
The base port address for the device may be configured via the
stx104_base module parameter.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 MAINTAINERS              |   6 ++
 drivers/iio/dac/Kconfig  |   8 +++
 drivers/iio/dac/Makefile |   1 +
 drivers/iio/dac/stx104.c | 178 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 193 insertions(+)
 create mode 100644 drivers/iio/dac/stx104.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 6ddb488..3905b31 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -763,6 +763,12 @@ L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
 S:	Maintained
 F:	sound/aoa/
 
+APEX EMBEDDED SYSTEMS STX104 DAC DRIVER
+M:	William Breathitt Gray <vilhelm.gray@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	drivers/iio/dac/stx104.c
+
 APM DRIVER
 M:	Jiri Kosina <jikos@kernel.org>
 S:	Odd fixes
diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 5dc7150..85295b1 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -206,4 +206,12 @@ config MCP4922
 	  To compile this driver as a module, choose M here: the module
 	  will be called mcp4922.
 
+config STX104
+	tristate "Apex Embedded Systems STX104 DAC driver"
+	depends on X86
+	help
+	  Say yes here to build support for the 2-channel DAC on the Apex Embedded
+	  Systems STX104 integrated analog PC/104 card. The base port address for
+	  the device may be configured via the stx104_base module parameter.
+
 endmenu
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index cb525b5..e2deda9 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -22,3 +22,4 @@ obj-$(CONFIG_MAX517) += max517.o
 obj-$(CONFIG_MAX5821) += max5821.o
 obj-$(CONFIG_MCP4725) += mcp4725.o
 obj-$(CONFIG_MCP4922) += mcp4922.o
+obj-$(CONFIG_STX104) += stx104.o
diff --git a/drivers/iio/dac/stx104.c b/drivers/iio/dac/stx104.c
new file mode 100644
index 0000000..3a887ae
--- /dev/null
+++ b/drivers/iio/dac/stx104.c
@@ -0,0 +1,178 @@
+/*
+ * DAC driver for the Apex Embedded Systems STX104
+ * Copyright (C) 2016 William Breathitt Gray
+ *
+ * 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.
+ *
+ * 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/bitops.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/platform_device.h>
+
+#define STX104_NUM_CHAN 2
+
+#define STX104_CHAN(chan) {				\
+	.type = IIO_VOLTAGE,				\
+	.channel = chan,				\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
+	.indexed = 1,					\
+	.output = 1					\
+}
+
+static unsigned stx104_base;
+module_param(stx104_base, uint, 0);
+MODULE_PARM_DESC(stx104_base, "Apex Embedded Systems STX104 base address");
+
+/**
+ * struct stx104_iio - IIO device private data structure
+ * @chan_out_states:	channels' output states
+ * @base:		base port address of the IIO device
+ */
+struct stx104_iio {
+	unsigned chan_out_states[STX104_NUM_CHAN];
+	unsigned base;
+};
+
+static int stx104_read_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
+{
+	struct stx104_iio *const priv = iio_priv(indio_dev);
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	*val = priv->chan_out_states[chan->channel];
+
+	return IIO_VAL_INT;
+}
+
+static int stx104_write_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int val, int val2, long mask)
+{
+	struct stx104_iio *const priv = iio_priv(indio_dev);
+	const unsigned chan_addr_offset = 2 * chan->channel;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	priv->chan_out_states[chan->channel] = val;
+	outw(val, priv->base + 4 + chan_addr_offset);
+
+	return 0;
+}
+
+static const struct iio_info stx104_info = {
+	.driver_module = THIS_MODULE,
+	.read_raw = stx104_read_raw,
+	.write_raw = stx104_write_raw
+};
+
+static const struct iio_chan_spec stx104_channels[STX104_NUM_CHAN] = {
+	STX104_CHAN(0),
+	STX104_CHAN(1)
+};
+
+static int __init stx104_probe(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev;
+	struct device *const dev = &pdev->dev;
+	struct stx104_iio *priv;
+	const unsigned extent = 16;
+	const char *const name = dev_name(dev);
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	if (!devm_request_region(dev, stx104_base, extent, name)) {
+		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
+			stx104_base, stx104_base + extent);
+		return -EBUSY;
+	}
+
+	indio_dev->info = &stx104_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = stx104_channels;
+	indio_dev->num_channels = STX104_NUM_CHAN;
+	indio_dev->name = name;
+
+	priv = iio_priv(indio_dev);
+	priv->base = stx104_base;
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	/* initialize DAC output to 0V */
+	outw(0, stx104_base + 4);
+	outw(0, stx104_base + 6);
+
+	return iio_device_register(indio_dev);
+}
+
+static int stx104_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+
+	iio_device_unregister(indio_dev);
+
+	return 0;
+}
+
+static struct platform_device *stx104_device;
+
+static struct platform_driver stx104_driver = {
+	.driver = {
+		.name = "stx104"
+	},
+	.remove = stx104_remove
+};
+
+static void __exit stx104_exit(void)
+{
+	platform_device_unregister(stx104_device);
+	platform_driver_unregister(&stx104_driver);
+}
+
+static int __init stx104_init(void)
+{
+	int err;
+
+	stx104_device = platform_device_alloc(stx104_driver.driver.name, -1);
+	if (!stx104_device)
+		return -ENOMEM;
+
+	err = platform_device_add(stx104_device);
+	if (err)
+		goto err_platform_device;
+
+	err = platform_driver_probe(&stx104_driver, stx104_probe);
+	if (err)
+		goto err_platform_driver;
+
+	return 0;
+
+err_platform_driver:
+	platform_device_del(stx104_device);
+err_platform_device:
+	platform_device_put(stx104_device);
+	return err;
+}
+
+module_init(stx104_init);
+module_exit(stx104_exit);
+
+MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
+MODULE_DESCRIPTION("Apex Embedded Systems STX104 DAC driver");
+MODULE_LICENSE("GPL v2");
-- 
2.4.10

Re: [PATCH] iio: Add IIO support for the DAC on the Apex Embedded Systems STX104

[Jonathan Cameron]

On 02/02/16 23:30, William Breathitt Gray wrote:
> The Apex Embedded Systems STX104 is a 16-channel 16-bit analog input and
> 2-channel 16-bit analog output PC/104 card. The STX104 incorporates a
> large one mega-sample FIFO.
> 
> This driver provides IIO support for the 2-channel DAC on the STX104.
> The base port address for the device may be configured via the
> stx104_base module parameter.
Nice looking product.
> 
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
I'm a little out of my depth wrt to the lack of discoverability of
this so perhaps take comments related to that rather more loosely
than the IIO stuff.

Clearly the IIO side of things is very simple, so not much there ;)

Jonathan
> ---
>  MAINTAINERS              |   6 ++
>  drivers/iio/dac/Kconfig  |   8 +++
>  drivers/iio/dac/Makefile |   1 +
>  drivers/iio/dac/stx104.c | 178 +++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 193 insertions(+)
>  create mode 100644 drivers/iio/dac/stx104.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 6ddb488..3905b31 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -763,6 +763,12 @@ L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
>  S:	Maintained
>  F:	sound/aoa/
>  
> +APEX EMBEDDED SYSTEMS STX104 DAC DRIVER
> +M:	William Breathitt Gray <vilhelm.gray@gmail.com>
> +L:	linux-iio@vger.kernel.org
> +S:	Maintained
> +F:	drivers/iio/dac/stx104.c
> +
>  APM DRIVER
>  M:	Jiri Kosina <jikos@kernel.org>
>  S:	Odd fixes
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index 5dc7150..85295b1 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -206,4 +206,12 @@ config MCP4922
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called mcp4922.
>  
> +config STX104
> +	tristate "Apex Embedded Systems STX104 DAC driver"
> +	depends on X86
> +	help
> +	  Say yes here to build support for the 2-channel DAC on the Apex Embedded
> +	  Systems STX104 integrated analog PC/104 card. The base port address for
> +	  the device may be configured via the stx104_base module parameter.
> +
Again, module parameter usage will restrict you to instantiating only
one instance.  Strikes me as a device where you might want more than one.
Does the hardware prevent this for some reason?
>  endmenu
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index cb525b5..e2deda9 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -22,3 +22,4 @@ obj-$(CONFIG_MAX517) += max517.o
>  obj-$(CONFIG_MAX5821) += max5821.o
>  obj-$(CONFIG_MCP4725) += mcp4725.o
>  obj-$(CONFIG_MCP4922) += mcp4922.o
> +obj-$(CONFIG_STX104) += stx104.o
> diff --git a/drivers/iio/dac/stx104.c b/drivers/iio/dac/stx104.c
> new file mode 100644
> index 0000000..3a887ae
> --- /dev/null
> +++ b/drivers/iio/dac/stx104.c
> @@ -0,0 +1,178 @@
> +/*
> + * DAC driver for the Apex Embedded Systems STX104
> + * Copyright (C) 2016 William Breathitt Gray
> + *
> + * 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.
> + *
> + * 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/bitops.h>
> +#include <linux/device.h>
> +#include <linux/errno.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/types.h>
> +#include <linux/io.h>
> +#include <linux/ioport.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/platform_device.h>
> +
> +#define STX104_NUM_CHAN 2
> +
> +#define STX104_CHAN(chan) {				\
> +	.type = IIO_VOLTAGE,				\
> +	.channel = chan,				\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
No information available on scale?
> +	.indexed = 1,					\
> +	.output = 1					\
> +}
> +
> +static unsigned stx104_base;
> +module_param(stx104_base, uint, 0);
> +MODULE_PARM_DESC(stx104_base, "Apex Embedded Systems STX104 base address");
> +
> +/**
> + * struct stx104_iio - IIO device private data structure
> + * @chan_out_states:	channels' output states
> + * @base:		base port address of the IIO device
> + */
> +struct stx104_iio {
> +	unsigned chan_out_states[STX104_NUM_CHAN];
> +	unsigned base;
> +};
> +
> +static int stx104_read_raw(struct iio_dev *indio_dev,
> +	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
> +{
> +	struct stx104_iio *const priv = iio_priv(indio_dev);
> +
> +	if (mask != IIO_CHAN_INFO_RAW)
> +		return -EINVAL;
> +
> +	*val = priv->chan_out_states[chan->channel];
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static int stx104_write_raw(struct iio_dev *indio_dev,
> +	struct iio_chan_spec const *chan, int val, int val2, long mask)
> +{
> +	struct stx104_iio *const priv = iio_priv(indio_dev);
> +	const unsigned chan_addr_offset = 2 * chan->channel;
> +
> +	if (mask != IIO_CHAN_INFO_RAW)
> +		return -EINVAL;
> +
> +	priv->chan_out_states[chan->channel] = val;
> +	outw(val, priv->base + 4 + chan_addr_offset);
> +
> +	return 0;
> +}
> +
> +static const struct iio_info stx104_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw = stx104_read_raw,
> +	.write_raw = stx104_write_raw
> +};
> +
> +static const struct iio_chan_spec stx104_channels[STX104_NUM_CHAN] = {
> +	STX104_CHAN(0),
> +	STX104_CHAN(1)
> +};
> +
> +static int __init stx104_probe(struct platform_device *pdev)
> +{
> +	struct iio_dev *indio_dev;
> +	struct device *const dev = &pdev->dev;
> +	struct stx104_iio *priv;
> +	const unsigned extent = 16;
> +	const char *const name = dev_name(dev);
Personally I'd not bother with the local name variable but just use
dev_name(dev) inline.
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	if (!devm_request_region(dev, stx104_base, extent, name)) {
> +		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
> +			stx104_base, stx104_base + extent);
> +		return -EBUSY;
> +	}
> +
> +	indio_dev->info = &stx104_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = stx104_channels;
> +	indio_dev->num_channels = STX104_NUM_CHAN;
> +	indio_dev->name = name;
> +
> +	priv = iio_priv(indio_dev);
> +	priv->base = stx104_base;
> +
> +	platform_set_drvdata(pdev, indio_dev);
> +
> +	/* initialize DAC output to 0V */
> +	outw(0, stx104_base + 4);
> +	outw(0, stx104_base + 6);
> +
> +	return iio_device_register(indio_dev);
> +}
> +
> +static int stx104_remove(struct platform_device *pdev)
> +{
> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> +
> +	iio_device_unregister(indio_dev);
If there really is nothing to be done other than unregister, then
use devm_iio_device_register(...) and you can drop the remove entirely.
> +
> +	return 0;
> +}
> +
> +static struct platform_device *stx104_device;
Again, this precludes more that one instance.  There should be a means of
avoiding this restriction.  A typical method would be to maintain a list
of instantiated devices rather than a single pointer.
> +
> +static struct platform_driver stx104_driver = {
> +	.driver = {
> +		.name = "stx104"
> +	},
> +	.remove = stx104_remove
> +};
> +
> +static void __exit stx104_exit(void)
> +{
> +	platform_device_unregister(stx104_device);
> +	platform_driver_unregister(&stx104_driver);
> +}
> +
> +static int __init stx104_init(void)
> +{
> +	int err;
> +
This is somewhat unusual, but fair enough if it is impossible to describe it any other
way on the system.

Any chance you'd ever have more than one on a system as I think this precludes doing
so as it stands.

My gut feeling would be to do this via a configfs interface, thus allowing clean
instantiation of instances of the device after the driver is probed.
> +	stx104_device = platform_device_alloc(stx104_driver.driver.name, -1);
> +	if (!stx104_device)
> +		return -ENOMEM;
> +
> +	err = platform_device_add(stx104_device);
> +	if (err)
> +		goto err_platform_device;
> +
> +	err = platform_driver_probe(&stx104_driver, stx104_probe);
> +	if (err)
> +		goto err_platform_driver;
> +
> +	return 0;
> +
> +err_platform_driver:
> +	platform_device_del(stx104_device);
> +err_platform_device:
> +	platform_device_put(stx104_device);
> +	return err;
> +}
> +
> +module_init(stx104_init);
> +module_exit(stx104_exit);
> +
> +MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
> +MODULE_DESCRIPTION("Apex Embedded Systems STX104 DAC driver");
> +MODULE_LICENSE("GPL v2");
> 

Re: [PATCH] iio: Add IIO support for the DAC on the Apex Embedded Systems STX104

[William Breathitt Gray]

On Sat, Feb 06, 2016 at 07:15:41PM +0000, Jonathan Cameron wrote:
>On 02/02/16 23:30, William Breathitt Gray wrote:
>> The Apex Embedded Systems STX104 is a 16-channel 16-bit analog input and
>> 2-channel 16-bit analog output PC/104 card. The STX104 incorporates a
>> large one mega-sample FIFO.
>> 
>> This driver provides IIO support for the 2-channel DAC on the STX104.
>> The base port address for the device may be configured via the
>> stx104_base module parameter.
>Nice looking product.
>> 
>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>I'm a little out of my depth wrt to the lack of discoverability of
>this so perhaps take comments related to that rather more loosely
>than the IIO stuff.

Unfortunately, the Apex Embedded Systems STX104 lacks hardware
discoverability functionality; users are expected to manually set the
base address of the card via physical jumpers, then point their software
to match the set base address of the card.

>Again, module parameter usage will restrict you to instantiating only
>one instance.  Strikes me as a device where you might want more than one.
>Does the hardware prevent this for some reason?

That is a good point; I overlooked the fact that my current
implementation restricts the module to only one instance. Since PC/104
cards are effectively ISA cards, instead of the platform driver I will
reimplement the module to use the ISA bus driver provided in the
linux/isa.h file. I will also allow users to pass in a list of base
addresses in order to support multiple instances.

>> +#define STX104_CHAN(chan) {				\
>> +	.type = IIO_VOLTAGE,				\
>> +	.channel = chan,				\
>> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
>No information available on scale?

I'm relatively new to the IIO subsystem, so let me know if I
misunderstood: the scale member allows users to view what output range
the device is set to use. The Apex Embedded Systems STX104 may be set to
one of four output voltage range modes: +-10V, +-5V, 0-10V, and 0-5V.
Unfortunately, these modes are configured via physical jumpers on the
card -- and because the card provides no hardware functionality to probe
for its configuration, the scale member should not be set since any
value would be at best a guess.

>> +	const char *const name = dev_name(dev);
>Personally I'd not bother with the local name variable but just use
>dev_name(dev) inline.

I'll incorporate this change in version 2 of this patch. 

>> +static int stx104_remove(struct platform_device *pdev)
>> +{
>> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>> +
>> +	iio_device_unregister(indio_dev);
>If there really is nothing to be done other than unregister, then
>use devm_iio_device_register(...) and you can drop the remove entirely.

Thanks, I wasn't aware of the devm_iio_device_register call! I'll
incorporate this change in version 2 of this patch. 

William Breathitt Gray

Re: [PATCH] iio: Add IIO support for the DAC on the Apex Embedded Systems STX104

[Jonathan Cameron]

On 8 February 2016 13:35:07 GMT+00:00, William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
>On Sat, Feb 06, 2016 at 07:15:41PM +0000, Jonathan Cameron wrote:
>>On 02/02/16 23:30, William Breathitt Gray wrote:
>>> The Apex Embedded Systems STX104 is a 16-channel 16-bit analog input
>and
>>> 2-channel 16-bit analog output PC/104 card. The STX104 incorporates
>a
>>> large one mega-sample FIFO.
>>> 
>>> This driver provides IIO support for the 2-channel DAC on the
>STX104.
>>> The base port address for the device may be configured via the
>>> stx104_base module parameter.
>>Nice looking product.
>>> 
>>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>>I'm a little out of my depth wrt to the lack of discoverability of
>>this so perhaps take comments related to that rather more loosely
>>than the IIO stuff.
>
>Unfortunately, the Apex Embedded Systems STX104 lacks hardware
>discoverability functionality; users are expected to manually set the
>base address of the card via physical jumpers, then point their
>software
>to match the set base address of the card.
>
>>Again, module parameter usage will restrict you to instantiating only
>>one instance.  Strikes me as a device where you might want more than
>one.
>>Does the hardware prevent this for some reason?
>
>That is a good point; I overlooked the fact that my current
>implementation restricts the module to only one instance. Since PC/104
>cards are effectively ISA cards, instead of the platform driver I will
>reimplement the module to use the ISA bus driver provided in the
>linux/isa.h file. I will also allow users to pass in a list of base
>addresses in order to support multiple instances.
Great.
>
>>> +#define STX104_CHAN(chan) {				\
>>> +	.type = IIO_VOLTAGE,				\
>>> +	.channel = chan,				\
>>> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
>>No information available on scale?
>
>I'm relatively new to the IIO subsystem, so let me know if I
>misunderstood: the scale member allows users to view what output range
>the device is set to use. The Apex Embedded Systems STX104 may be set
>to
>one of four output voltage range modes: +-10V, +-5V, 0-10V, and 0-5V.
>Unfortunately, these modes are configured via physical jumpers on the
>card -- and because the card provides no hardware functionality to
>probe
>for its configuration, the scale member should not be set since any
>value would be at best a guess.
You are correct. If unknown as here just not providing it is best option.
>
>>> +	const char *const name = dev_name(dev);
>>Personally I'd not bother with the local name variable but just use
>>dev_name(dev) inline.
>
>I'll incorporate this change in version 2 of this patch. 
>
>>> +static int stx104_remove(struct platform_device *pdev)
>>> +{
>>> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>>> +
>>> +	iio_device_unregister(indio_dev);
>>If there really is nothing to be done other than unregister, then
>>use devm_iio_device_register(...) and you can drop the remove
>entirely.
>
>Thanks, I wasn't aware of the devm_iio_device_register call! I'll
>incorporate this change in version 2 of this patch. 
>
>William Breathitt Gray

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