Re: [PATCH 2/4] iio: dac: add support for stm32 DAC

[Fabrice Gasnier]

On 04/01/2017 02:34 PM, Peter Meerwald-Stadler wrote:
> On Fri, 31 Mar 2017, Fabrice Gasnier wrote:
> 
>> Add support for STMicroelectronics STM32 DAC. It's a 12-bit, voltage
>> output digital-to-analog converter. It has two output channels, each
>> with its own converter.
>> It supports 8 bits or 12bits left/right aligned data format. Only
>> 12bits right-aligned is used here. It has built-in noise or
>> triangle waveform generator, and supports external triggers for
>> conversions.
>> Each channel can be used independently, with separate trigger, then
>> separate IIO devices are used to handle this. Core driver is intended
>> to share common resources such as clock, reset, reference voltage and
>> registers.
> 
> comments below

Hi Peter,

Thanks for reviewing.
I'll update V2 with all your remarks (comments bellow).

Best Regards,
Fabrice

>  
>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
>> ---
>>  drivers/iio/dac/Kconfig          |  15 ++
>>  drivers/iio/dac/Makefile         |   2 +
>>  drivers/iio/dac/stm32-dac-core.c | 180 ++++++++++++++++++++++++
>>  drivers/iio/dac/stm32-dac-core.h |  51 +++++++
>>  drivers/iio/dac/stm32-dac.c      | 296 +++++++++++++++++++++++++++++++++++++++
>>  5 files changed, 544 insertions(+)
>>  create mode 100644 drivers/iio/dac/stm32-dac-core.c
>>  create mode 100644 drivers/iio/dac/stm32-dac-core.h
>>  create mode 100644 drivers/iio/dac/stm32-dac.c
>>
>> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
>> index d3084028..7198648 100644
>> --- a/drivers/iio/dac/Kconfig
>> +++ b/drivers/iio/dac/Kconfig
>> @@ -274,6 +274,21 @@ config MCP4922
>>  	  To compile this driver as a module, choose M here: the module
>>  	  will be called mcp4922.
>>  
>> +config STM32_DAC
>> +	tristate "STMicroelectronics STM32 DAC"
>> +	depends on (ARCH_STM32 && OF) || COMPILE_TEST
>> +	depends on REGULATOR
>> +	select STM32_DAC_CORE
>> +	help
>> +	  Say yes here to build support for STMicroelectronics STM32 Digital
>> +	  to Analog Converter (DAC).
>> +
>> +	  This driver can also be built as a module.  If so, the module
>> +	  will be called stm32-dac.
>> +
>> +config STM32_DAC_CORE
>> +	tristate
>> +
>>  config VF610_DAC
>>  	tristate "Vybrid vf610 DAC driver"
>>  	depends on OF
>> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
>> index f01bf4a..afe8ae7 100644
>> --- a/drivers/iio/dac/Makefile
>> +++ b/drivers/iio/dac/Makefile
>> @@ -29,4 +29,6 @@ obj-$(CONFIG_MAX517) += max517.o
>>  obj-$(CONFIG_MAX5821) += max5821.o
>>  obj-$(CONFIG_MCP4725) += mcp4725.o
>>  obj-$(CONFIG_MCP4922) += mcp4922.o
>> +obj-$(CONFIG_STM32_DAC_CORE) += stm32-dac-core.o
>> +obj-$(CONFIG_STM32_DAC) += stm32-dac.o
>>  obj-$(CONFIG_VF610_DAC) += vf610_dac.o
>> diff --git a/drivers/iio/dac/stm32-dac-core.c b/drivers/iio/dac/stm32-dac-core.c
>> new file mode 100644
>> index 0000000..75e4878
>> --- /dev/null
>> +++ b/drivers/iio/dac/stm32-dac-core.c
>> @@ -0,0 +1,180 @@
>> +/*
>> + * This file is part of STM32 DAC driver
>> + *
>> + * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
>> + * Author: Fabrice Gasnier <fabrice.gasnier@xxxxxx>.
>> + *
>> + * License type: GPLv2
>> + *
>> + * 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.
>> + *
>> + * You should have received a copy of the GNU General Public License along with
>> + * this program. If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/clk.h>
>> +#include <linux/delay.h>
>> +#include <linux/module.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/regulator/consumer.h>
>> +#include <linux/reset.h>
>> +
>> +#include "stm32-dac-core.h"
>> +
>> +/**
>> + * struct stm32_dac_priv - stm32 DAC core private data
>> + * @pclk:		peripheral clock common for all DACs
>> + * @rst:		peripheral reset control
>> + * @vref:		regulator reference
>> + * @common:		Common data for all DAC instances
>> + */
>> +struct stm32_dac_priv {
>> +	struct clk *pclk;
>> +	struct reset_control *rst;
>> +	struct regulator *vref;
>> +	struct stm32_dac_common common;
>> +};
>> +
>> +static struct stm32_dac_priv *to_stm32_dac_priv(struct stm32_dac_common *com)
>> +{
>> +	return container_of(com, struct stm32_dac_priv, common);
>> +}
>> +
>> +static const struct regmap_config stm32_dac_regmap_cfg = {
>> +	.reg_bits = 32,
>> +	.val_bits = 32,
>> +	.reg_stride = sizeof(u32),
>> +	.max_register = 0x3fc,
>> +};
>> +
>> +static int stm32_dac_probe(struct platform_device *pdev)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct stm32_dac_priv *priv;
>> +	struct regmap *regmap;
>> +	struct resource *res;
>> +	void __iomem *mmio;
>> +	int ret;
>> +
>> +	if (!dev->of_node)
>> +		return -ENODEV;
>> +
>> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>> +	if (!priv)
>> +		return -ENOMEM;
>> +
>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	mmio = devm_ioremap_resource(dev, res);
>> +	if (IS_ERR(mmio))
>> +		return PTR_ERR(mmio);
>> +
>> +	regmap = devm_regmap_init_mmio(dev, mmio, &stm32_dac_regmap_cfg);
>> +	if (IS_ERR(regmap))
>> +		return PTR_ERR(regmap);
>> +	priv->common.regmap = regmap;
>> +
>> +	priv->vref = devm_regulator_get(dev, "vref");
>> +	if (IS_ERR(priv->vref)) {
>> +		ret = PTR_ERR(priv->vref);
>> +		dev_err(dev, "vref get failed, %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	ret = regulator_enable(priv->vref);
>> +	if (ret < 0) {
>> +		dev_err(dev, "vref enable failed\n");
>> +		return ret;
>> +	}
>> +
>> +	ret = regulator_get_voltage(priv->vref);
>> +	if (ret < 0) {
>> +		dev_err(dev, "vref get voltage failed, %d\n", ret);
>> +		goto err_vref;
>> +	}
>> +	priv->common.vref_mv = ret / 1000;
>> +	dev_dbg(dev, "vref+=%dmV\n", priv->common.vref_mv);
>> +
>> +	priv->pclk = devm_clk_get(dev, "pclk");
>> +	if (IS_ERR(priv->pclk)) {
>> +		ret = PTR_ERR(priv->pclk);
>> +		dev_err(dev, "pclk get failed\n");
>> +		goto err_vref;
>> +	}
>> +
>> +	ret = clk_prepare_enable(priv->pclk);
>> +	if (ret < 0) {
>> +		dev_err(dev, "pclk enable failed\n");
>> +		goto err_vref;
>> +	}
>> +
>> +	priv->rst = devm_reset_control_get(dev, NULL);
>> +	if (!IS_ERR(priv->rst)) {
>> +		reset_control_assert(priv->rst);
>> +		udelay(2);
>> +		reset_control_deassert(priv->rst);
>> +	}
>> +
>> +	/* When clock speed is higher than 80MHz, set HFSEL */
>> +	priv->common.hfsel = (clk_get_rate(priv->pclk) > 80000000UL);
>> +	ret = regmap_update_bits(regmap, STM32_DAC_CR, STM32H7_DAC_CR_HFSEL,
>> +				 priv->common.hfsel ? STM32H7_DAC_CR_HFSEL : 0);
>> +	if (ret)
>> +		goto err_pclk;
>> +
>> +	platform_set_drvdata(pdev, &priv->common);
>> +
>> +	ret = of_platform_populate(pdev->dev.of_node, NULL, NULL, dev);
>> +	if (ret < 0) {
>> +		dev_err(dev, "failed to populate DT children\n");
>> +		goto err_pclk;
>> +	}
>> +
>> +	return 0;
>> +
>> +err_pclk:
>> +	clk_disable_unprepare(priv->pclk);
>> +err_vref:
>> +	regulator_disable(priv->vref);
>> +
>> +	return ret;
>> +}
>> +
>> +static int stm32_dac_remove(struct platform_device *pdev)
>> +{
>> +	struct stm32_dac_common *common = platform_get_drvdata(pdev);
>> +	struct stm32_dac_priv *priv = to_stm32_dac_priv(common);
>> +
>> +	of_platform_depopulate(&pdev->dev);
>> +	clk_disable_unprepare(priv->pclk);
>> +	regulator_disable(priv->vref);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id stm32_dac_of_match[] = {
>> +	{ .compatible = "st,stm32h7-dac-core", },
>> +	{},
>> +};
>> +MODULE_DEVICE_TABLE(of, stm32_dac_of_match);
>> +
>> +static struct platform_driver stm32_dac_driver = {
>> +	.probe = stm32_dac_probe,
>> +	.remove = stm32_dac_remove,
>> +	.driver = {
>> +		.name = "stm32-dac-core",
>> +		.of_match_table = stm32_dac_of_match,
>> +	},
>> +};
>> +module_platform_driver(stm32_dac_driver);
>> +
>> +MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@xxxxxx>");
>> +MODULE_DESCRIPTION("STMicroelectronics STM32 DAC core driver");
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_ALIAS("platform:stm32-dac-core");
>> diff --git a/drivers/iio/dac/stm32-dac-core.h b/drivers/iio/dac/stm32-dac-core.h
>> new file mode 100644
>> index 0000000..d3099f7
>> --- /dev/null
>> +++ b/drivers/iio/dac/stm32-dac-core.h
>> @@ -0,0 +1,51 @@
>> +/*
>> + * This file is part of STM32 DAC driver
>> + *
>> + * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
>> + * Author: Fabrice Gasnier <fabrice.gasnier@xxxxxx>.
>> + *
>> + * License type: GPLv2
>> + *
>> + * 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.
>> + *
>> + * You should have received a copy of the GNU General Public License along with
>> + * this program. If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#ifndef __STM32_DAC_CORE_H
>> +#define __STM32_DAC_CORE_H
>> +
>> +#include <linux/regmap.h>
>> +
>> +/* STM32 DAC registers */
>> +#define STM32_DAC_CR		0x00
>> +#define STM32_DAC_DHR12R1	0x08
>> +#define STM32_DAC_DHR12R2	0x14
>> +#define STM32_DAC_DOR1		0x2C
>> +#define STM32_DAC_DOR2		0x30
>> +
>> +/* STM32_DAC_CR bit fields */
>> +#define STM32_DAC_CR_EN1		BIT(0)
>> +#define STM32H7_DAC_CR_HFSEL		BIT(15)
>> +#define STM32_DAC_CR_EN2		BIT(16)
>> +
>> +/**
>> + * struct stm32_dac_common - stm32 DAC driver common data (for all instances)
>> + * @regmap: DAC registers shared via regmap
>> + * @vref_mv: reference voltage (mv)
>> + * @hfsel: high speed bus clock
> 
> probably better "high speed bus clock selected"
Ok

> 
>> + */
>> +struct stm32_dac_common {
>> +	struct regmap			*regmap;
>> +	int				vref_mv;
>> +	bool				hfsel;
>> +};
>> +
>> +#endif
>> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
>> new file mode 100644
>> index 0000000..ee9711d
>> --- /dev/null
>> +++ b/drivers/iio/dac/stm32-dac.c
>> @@ -0,0 +1,296 @@
>> +/*
>> + * This file is part of STM32 DAC driver
>> + *
>> + * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
>> + * Authors: Amelie Delaunay <amelie.delaunay@xxxxxx>
>> + *	    Fabrice Gasnier <fabrice.gasnier@xxxxxx>
>> + *
>> + * License type: GPLv2
>> + *
>> + * 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.
>> + *
>> + * You should have received a copy of the GNU General Public License along with
>> + * this program. If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/bitfield.h>
>> +#include <linux/delay.h>
>> +#include <linux/iio/iio.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +
>> +#include "stm32-dac-core.h"
>> +
>> +#define STM32_DAC_CHANNEL_1		1
>> +#define STM32_DAC_CHANNEL_2		2
>> +
>> +/**
>> + * struct stm32_dac - private data of DAC driver
>> + * @common:		reference to DAC common data
>> + */
>> +struct stm32_dac {
>> +	struct stm32_dac_common *common;
>> +};
>> +
>> +static int stm32_dac_is_enabled(struct stm32_dac *dac, int channel)
>> +{
>> +	u32 en, val;
>> +	int ret;
>> +
>> +	ret = regmap_read(dac->common->regmap, STM32_DAC_CR, &val);
>> +	if (ret < 0)
>> +		return ret;
>> +	if (channel == STM32_DAC_CHANNEL_1)
>> +		en = FIELD_GET(STM32_DAC_CR_EN1, val);
>> +	else
>> +		en = FIELD_GET(STM32_DAC_CR_EN2, val);
>> +
>> +	return !!en;
>> +}
>> +
>> +static int stm32_dac_enable(struct iio_dev *indio_dev, int channel)
>> +{
>> +	struct stm32_dac *dac = iio_priv(indio_dev);
>> +	u32 en = (channel == STM32_DAC_CHANNEL_1) ?
>> +		STM32_DAC_CR_EN1 : STM32_DAC_CR_EN2;
> 
> could #define a macro to select CR_EN1 or CR_EN2 depending on channel; to 
> use here and above and below

I also thought about it earlier, but... I'll define a macro in V2.
> 
> or maybe a table to select all the channel-specific constants indexed by 
> channel
> 
>> +	int ret;
>> +
>> +	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, en, en);
>> +	if (ret < 0) {
>> +		dev_err(&indio_dev->dev, "Enable failed\n");
>> +		return ret;
>> +	}
>> +
>> +	/*
>> +	 * When HFSEL is set, it is not allowed to write the DHRx register
>> +	 * during 8 clock cycles after the ENx bit is set. It is not allowed
>> +	 * to make software/hardware trigger during this period neither.
> 
> neither -> either
Ok
> 
>> +	 */
>> +	if (dac->common->hfsel)
>> +		udelay(1);
>> +
>> +	return 0;
>> +}
>> +
>> +static int stm32_dac_disable(struct iio_dev *indio_dev, int channel)
>> +{
>> +	struct stm32_dac *dac = iio_priv(indio_dev);
>> +	u32 en = (channel == STM32_DAC_CHANNEL_1) ?
>> +		STM32_DAC_CR_EN1 : STM32_DAC_CR_EN2;
>> +	int ret;
>> +
>> +	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, en, 0);
>> +	if (ret)
>> +		dev_err(&indio_dev->dev, "Disable failed\n");
>> +
>> +	return ret;
>> +}
>> +
>> +static int stm32_dac_get_value(struct stm32_dac *dac, int channel, int *val)
>> +{
>> +	int ret;
>> +
>> +	if (channel == STM32_DAC_CHANNEL_1)
>> +		ret = regmap_read(dac->common->regmap, STM32_DAC_DOR1, val);
>> +	else
>> +		ret = regmap_read(dac->common->regmap, STM32_DAC_DOR2, val);
>> +
>> +	return ret ? ret : IIO_VAL_INT;
>> +}
>> +
>> +static int stm32_dac_set_value(struct stm32_dac *dac, int channel, int val)
>> +{
>> +	int ret;
>> +
>> +	if (channel == STM32_DAC_CHANNEL_1)
>> +		ret = regmap_write(dac->common->regmap, STM32_DAC_DHR12R1, val);
>> +	else
>> +		ret = regmap_write(dac->common->regmap, STM32_DAC_DHR12R2, val);
>> +
>> +	return ret;
>> +}
>> +
>> +static int stm32_dac_read_raw(struct iio_dev *indio_dev,
>> +			      struct iio_chan_spec const *chan,
>> +			      int *val, int *val2, long mask)
>> +{
>> +	struct stm32_dac *dac = iio_priv(indio_dev);
>> +	int ret;
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_RAW:
>> +		return stm32_dac_get_value(dac, chan->channel, val);
>> +	case IIO_CHAN_INFO_SCALE:
>> +		*val = dac->common->vref_mv;
>> +		*val2 = chan->scan_type.realbits;
>> +		return IIO_VAL_FRACTIONAL_LOG2;
>> +	case IIO_CHAN_INFO_ENABLE:
>> +		ret = stm32_dac_is_enabled(dac, chan->channel);
>> +		if (ret < 0)
>> +			return ret;
>> +		*val = ret;
>> +		return IIO_VAL_INT;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +}
>> +
>> +static int stm32_dac_write_raw(struct iio_dev *indio_dev,
>> +			       struct iio_chan_spec const *chan,
>> +			       int val, int val2, long mask)
>> +{
>> +	struct stm32_dac *dac = iio_priv(indio_dev);
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_RAW:
>> +		return stm32_dac_set_value(dac, chan->channel, val);
>> +	case IIO_CHAN_INFO_ENABLE:
>> +		if (!!val)
>> +			return stm32_dac_enable(indio_dev, chan->channel);
>> +		else
>> +			return stm32_dac_disable(indio_dev, chan->channel);
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +}
>> +
>> +static int stm32_dac_debugfs_reg_access(struct iio_dev *indio_dev,
>> +					unsigned reg, unsigned writeval,
>> +					unsigned *readval)
>> +{
>> +	struct stm32_dac *dac = iio_priv(indio_dev);
>> +
>> +	if (!readval)
>> +		return regmap_write(dac->common->regmap, reg, writeval);
>> +	else
>> +		return regmap_read(dac->common->regmap, reg, readval);
>> +}
>> +
>> +static const struct iio_info stm32_dac_iio_info = {
>> +	.read_raw = &stm32_dac_read_raw,
> 
> no & for functions (matter of taste)
I'll remove these.
> 
>> +	.write_raw = &stm32_dac_write_raw,
>> +	.debugfs_reg_access = &stm32_dac_debugfs_reg_access,
>> +	.driver_module = THIS_MODULE,
>> +};
>> +
>> +#define STM32_DAC_CHANNEL(chan, name) {		\
>> +	.type = IIO_VOLTAGE,			\
>> +	.indexed = 1,				\
>> +	.output = 1,				\
>> +	.channel = chan,			\
>> +	.info_mask_separate =			\
>> +		BIT(IIO_CHAN_INFO_RAW) |	\
>> +		BIT(IIO_CHAN_INFO_ENABLE) |	\
>> +		BIT(IIO_CHAN_INFO_SCALE),	\
>> +	.scan_type = {				\
> 
> scan_type is no needed (yet) and scan_index is missing (or always 0 which 
> becomes clear below, a comment may be helpful)
> 
>> +		.sign = 'u',			\
>> +		.realbits = 12,			\
>> +		.storagebits = 16,		\
>> +	},					\
>> +	.datasheet_name = name,			\
>> +}
>> +
>> +static const struct iio_chan_spec stm32_dac_channels[] = {
>> +	STM32_DAC_CHANNEL(STM32_DAC_CHANNEL_1, "out1"),
>> +	STM32_DAC_CHANNEL(STM32_DAC_CHANNEL_2, "out2"),
>> +};
>> +
>> +static int stm32_dac_chan_of_init(struct iio_dev *indio_dev)
>> +{
>> +	struct device_node *np = indio_dev->dev.of_node;
>> +	unsigned int i;
>> +	u32 channel;
>> +	int ret;
>> +
>> +	ret = of_property_read_u32(np, "st,dac-channel", &channel);
>> +	if (ret) {
>> +		dev_err(&indio_dev->dev, "Failed to read st,dac-channel\n");
>> +		return ret;
>> +	}
>> +
>> +	for (i = 0; i < ARRAY_SIZE(stm32_dac_channels); i++) {
>> +		if (stm32_dac_channels[i].channel == channel)
>> +			break;
>> +	}
>> +	if (i >= ARRAY_SIZE(stm32_dac_channels)) {
>> +		dev_err(&indio_dev->dev, "Invalid st,dac-channel\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	indio_dev->channels = &stm32_dac_channels[i];
>> +	indio_dev->num_channels = 1;
> 
> this is unusual, a comment would be helpful
> why not expose both channels?
Got it, I'll comment about this.

> 
>> +
>> +	return 0;
>> +};
>> +
>> +static int stm32_dac_probe(struct platform_device *pdev)
>> +{
>> +	struct device_node *np = pdev->dev.of_node;
>> +	struct iio_dev *indio_dev;
>> +	struct stm32_dac *dac;
>> +	int ret;
>> +
>> +	if (!np)
>> +		return -ENODEV;
>> +
>> +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*dac));
>> +	if (!indio_dev)
>> +		return -ENOMEM;
>> +	platform_set_drvdata(pdev, indio_dev);
>> +
>> +	dac = iio_priv(indio_dev);
>> +	dac->common = dev_get_drvdata(pdev->dev.parent);
>> +	indio_dev->name = dev_name(&pdev->dev);
>> +	indio_dev->dev.parent = &pdev->dev;
>> +	indio_dev->dev.of_node = pdev->dev.of_node;
>> +	indio_dev->info = &stm32_dac_iio_info;
>> +	indio_dev->modes = INDIO_DIRECT_MODE;
>> +
>> +	ret = stm32_dac_chan_of_init(indio_dev);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	ret = iio_device_register(indio_dev);
> 
> just 
> return iio_device_register();
> 
> candidate for devm_ due to empty _remove()
You're right.

I didn't use devm_ due to patch 3: It needs .remove routine.
But okay, I'll do this anyway :-)

> 
>> +	if (ret)
>> +		return ret;
>> +
>> +	return 0;
>> +}
>> +
>> +static int stm32_dac_remove(struct platform_device *pdev)
>> +{
>> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>> +
>> +	iio_device_unregister(indio_dev);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id stm32_dac_of_match[] = {
>> +	{ .compatible = "st,stm32-dac", },
>> +	{},
>> +};
>> +MODULE_DEVICE_TABLE(of, stm32_dac_of_match);
>> +
>> +static struct platform_driver stm32_dac_driver = {
>> +	.probe = stm32_dac_probe,
>> +	.remove = stm32_dac_remove,
>> +	.driver = {
>> +		.name = "stm32-dac",
>> +		.of_match_table = stm32_dac_of_match,
>> +	},
>> +};
>> +module_platform_driver(stm32_dac_driver);
>> +
>> +MODULE_ALIAS("platform:stm32-dac");
>> +MODULE_AUTHOR("Amelie Delaunay <amelie.delaunay@xxxxxx>");
>> +MODULE_DESCRIPTION("STMicroelectronics STM32 DAC driver");
>> +MODULE_LICENSE("GPL v2");
>>
>