Re: [PATCH v4 05/12] IIO: ADC: add sigma delta modulator support

[Jonathan Cameron <jic23-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Thu, 9 Nov 2017 11:12:27 +0100
Arnaud Pouliquen <arnaud.pouliquen-qxv4g6HH51o@public.gmane.org> wrote:

> Add generic driver to support sigma delta modulators.
A trivial comment inline..

> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen-qxv4g6HH51o@public.gmane.org>
> ---
>  drivers/iio/adc/Kconfig            | 12 ++++++
>  drivers/iio/adc/Makefile           |  1 +
>  drivers/iio/adc/sd_adc_modulator.c | 82 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 95 insertions(+)
>  create mode 100644 drivers/iio/adc/sd_adc_modulator.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 5762565..c5db62f 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -626,6 +626,18 @@ config SPEAR_ADC
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called spear_adc.
>  
> +config SD_ADC_MODULATOR
> +	tristate "Generic sigma delta modulator"
> +	depends on OF
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
> +	help
> +	  Select this option to enables sigma delta modulator. This driver can
> +	  support generic sigma delta modulators.
> +
> +	  This driver can also be built as a module.  If so, the module
> +	  will be called sd_adc_modulator.
> +
>  config STM32_ADC_CORE
>  	tristate "STMicroelectronics STM32 adc core"
>  	depends on ARCH_STM32 || COMPILE_TEST
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 9874e05..d800325 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -81,3 +81,4 @@ obj-$(CONFIG_VF610_ADC) += vf610_adc.o
>  obj-$(CONFIG_VIPERBOARD_ADC) += viperboard_adc.o
>  xilinx-xadc-y := xilinx-xadc-core.o xilinx-xadc-events.o
>  obj-$(CONFIG_XILINX_XADC) += xilinx-xadc.o
> +obj-$(CONFIG_SD_ADC_MODULATOR) += sd_adc_modulator.o
> diff --git a/drivers/iio/adc/sd_adc_modulator.c b/drivers/iio/adc/sd_adc_modulator.c
> new file mode 100644
> index 0000000..ff2504a
> --- /dev/null
> +++ b/drivers/iio/adc/sd_adc_modulator.c
> @@ -0,0 +1,82 @@
> +/*
> + * Generic sigma delta modulator driver
> + *
> + * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
> + * Author: Arnaud Pouliquen <arnaud.pouliquen-qxv4g6HH51o@public.gmane.org>.
> + *
> + * 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/iio/iio.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +
> +static const struct iio_info iio_sd_mod_iio_info;
> +
> +static const struct iio_chan_spec iio_sd_mod_ch = {
> +	.type = IIO_VOLTAGE,
> +	.indexed = 1,
> +	.scan_index = 0,

Don't specify a scan index until you add buffered support.
Actually scan type isn't usually supplied until then either, but
here it kind of acts as documentation of the odd nature of this
device.

> +	.scan_type = {
> +		.sign = 'u',
> +		.realbits = 1,
> +		.shift = 0,
> +	},
> +};
> +
> +static int iio_sd_mod_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct iio_dev *iio;
> +
> +	iio = devm_iio_device_alloc(dev, 0);
> +	if (!iio)
> +		return -ENOMEM;
> +
> +	iio->dev.parent = dev;
> +	iio->dev.of_node = dev->of_node;
> +	iio->name = dev_name(dev);
> +	iio->info = &iio_sd_mod_iio_info;
> +	iio->modes = INDIO_BUFFER_HARDWARE;
> +
> +	iio->num_channels = 1;
> +	iio->channels = &iio_sd_mod_ch;
> +
> +	platform_set_drvdata(pdev, iio);
> +
> +	return devm_iio_device_register(&pdev->dev, iio);
> +}
> +
> +static const struct of_device_id sd_adc_of_match[] = {
> +	{ .compatible = "sd-modulator" },
> +	{ .compatible = "ads1201" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, sd_adc_of_match);
> +
> +static struct platform_driver iio_sd_mod_adc = {
> +	.driver = {
> +		.name = "iio_sd_adc_mod",
> +		.of_match_table = of_match_ptr(sd_adc_of_match),
> +	},
> +	.probe = iio_sd_mod_probe,
> +};
> +
> +module_platform_driver(iio_sd_mod_adc);
> +
> +MODULE_DESCRIPTION("Basic sigma delta modulator");
> +MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen-qxv4g6HH51o@public.gmane.org>");
> +MODULE_LICENSE("GPL v2");

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