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Date:	Sat, 21 Jun 2014 11:53:05 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Michael Welling <mwelling@...e.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald <pmeerw@...erw.net>, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] iio: dac: mcp4902/mcp4912/mcp4922 dac driver

On 15/06/14 22:17, Michael Welling wrote:
> This patch provides an iio device driver for the Microchip
> MCP49x2 series DACs.
>
Normally this lot goes below the --- inorder that it doesn't then lead
to really long commit messages in git.  Anyhow, I just dropped this stuff
during the commit.  It's enough to have it in the list archives.
> v5:
> - Removes wildcard naming in filename and variables.
> - Switches to using iio_device_register/unregister to avoid race condition.
> - Removes --- around help in the Kconfig entry.
> - Removes unused variable.
> - Adds checking for val2 in write_raw function.
>
> v4:
> - Removes use of old IIO_ST macro.
> - Moves mosi variable to the state struct.
> - Removes default vref of 2.5v.
>
> v3:
> - Removes MCP49X2_RES_MASK and uses GENMASK directly.
> - Switch from using address to channel in functions.
>
> v2:
> - Switched to using GENMASK instead of creating a mask directly.
> - Switched from using address to channel.
> - Removed unnecessary feilds from channel macro.
> - Made SPI buffer cachline aligned.
> - Removed some uncessary bounds checking.
> - Report -EINVAL when writing a value beyond the range to DAC.
> - Switched to devm_iio_device_alloc.
> - Created a constant for the number of channels.
> - Switched to devm_ioo_device_register.
>
> Signed-off-by: Michael Welling <mwelling@...e.org>
Applied to the togreg branch of iio.git.  Note this is initially pushed
out as testing to allow the autobuilders to do there work before I commit
to not rebasing the tree!

Thanks for your hard work on this.  It's a nice little driver!

Jonathan
> ---
>   drivers/iio/dac/Kconfig   |   10 +++
>   drivers/iio/dac/Makefile  |    1 +
>   drivers/iio/dac/mcp4922.c |  216 +++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 227 insertions(+)
>   create mode 100644 drivers/iio/dac/mcp4922.c
>
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index f378ca8..f278eff 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 MCP4922
> +	tristate "MCP4902, MCP4912, MCP4922 DAC driver"
> +	depends on SPI
> +	help
> +	  Say yes here to build the driver for the Microchip MCP4902
> +	  MCP4912, and MCP4922 DAC devices.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called mcp4922.
> +
>   endmenu
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index bb84ad6..1010764 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_MCP4922) += mcp4922.o
> diff --git a/drivers/iio/dac/mcp4922.c b/drivers/iio/dac/mcp4922.c
> new file mode 100644
> index 0000000..92cf4ca
> --- /dev/null
> +++ b/drivers/iio/dac/mcp4922.c
> @@ -0,0 +1,216 @@
> +/*
> + * mcp4922.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>
> +#include <linux/bitops.h>
> +
> +#define MCP4922_NUM_CHANNELS	2
> +
> +enum mcp4922_supported_device_ids {
> +	ID_MCP4902,
> +	ID_MCP4912,
> +	ID_MCP4922,
> +};
> +
> +struct mcp4922_state {
> +	struct spi_device *spi;
> +	unsigned int value[MCP4922_NUM_CHANNELS];
> +	unsigned int vref_mv;
> +	struct regulator *vref_reg;
> +	u8 mosi[2] ____cacheline_aligned;
> +};
> +
> +#define MCP4922_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),	\
> +	.scan_type = {					\
> +		.sign = 'u',				\
> +		.realbits = (bits),			\
> +		.storagebits = 16,			\
> +		.shift = 12 - (bits),			\
> +	},						\
> +}
> +
> +static int mcp4922_spi_write(struct mcp4922_state *state, u8 addr, u32 val)
> +{
> +	state->mosi[1] = val & 0xff;
> +	state->mosi[0] = (addr == 0) ? 0x00 : 0x80;
> +	state->mosi[0] |= 0x30 | ((val >> 8) & 0x0f);
> +
> +	return spi_write(state->spi, state->mosi, 2);
> +}
> +
> +static int mcp4922_read_raw(struct iio_dev *indio_dev,
> +		struct iio_chan_spec const *chan,
> +		int *val,
> +		int *val2,
> +		long mask)
> +{
> +	struct mcp4922_state *state = iio_priv(indio_dev);
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		*val = state->value[chan->channel];
> +		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 mcp4922_write_raw(struct iio_dev *indio_dev,
> +		struct iio_chan_spec const *chan,
> +		int val,
> +		int val2,
> +		long mask)
> +{
> +	struct mcp4922_state *state = iio_priv(indio_dev);
> +
> +	if (val2 != 0)
> +		return -EINVAL;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (val > GENMASK(chan->scan_type.realbits-1, 0))
> +			return -EINVAL;
> +		val <<= chan->scan_type.shift;
> +		state->value[chan->channel] = val;
> +		return mcp4922_spi_write(state, chan->channel, val);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_chan_spec mcp4922_channels[3][MCP4922_NUM_CHANNELS] = {
> +	[ID_MCP4902] = { MCP4922_CHAN(0, 8),	MCP4922_CHAN(1, 8) },
> +	[ID_MCP4912] = { MCP4922_CHAN(0, 10),	MCP4922_CHAN(1, 10) },
> +	[ID_MCP4922] = { MCP4922_CHAN(0, 12),	MCP4922_CHAN(1, 12) },
> +};
> +
> +static const struct iio_info mcp4922_info = {
> +	.read_raw = &mcp4922_read_raw,
> +	.write_raw = &mcp4922_write_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static int mcp4922_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct mcp4922_state *state;
> +	const struct spi_device_id *id;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
> +	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)) {
> +		dev_err(&spi->dev, "Vref regulator not specified\n");
> +		return PTR_ERR(state->vref_reg);
> +	}
> +
> +	ret = regulator_enable(state->vref_reg);
> +	if (ret) {
> +		dev_err(&spi->dev, "Failed to enable vref regulator: %d\n",
> +				ret);
> +		return ret;
> +	}
> +
> +	ret = regulator_get_voltage(state->vref_reg);
> +	if (ret < 0) {
> +		dev_err(&spi->dev, "Failed to read vref regulator: %d\n",
> +				ret);
> +		goto error_disable_reg;
> +	}
> +	state->vref_mv = ret / 1000;
> +
> +	spi_set_drvdata(spi, indio_dev);
> +	id = spi_get_device_id(spi);
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->info = &mcp4922_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = mcp4922_channels[id->driver_data];
> +	indio_dev->num_channels = MCP4922_NUM_CHANNELS;
> +	indio_dev->name = id->name;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret) {
> +		dev_err(&spi->dev, "Failed to register iio device: %d\n",
> +				ret);
> +		goto error_disable_reg;
> +	}
> +
> +	return 0;
> +
> +error_disable_reg:
> +	regulator_disable(state->vref_reg);
> +
> +	return ret;
> +}
> +
> +static int mcp4922_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct mcp4922_state *state;
> +
> +	iio_device_unregister(indio_dev);
> +	state = iio_priv(indio_dev);
> +	regulator_disable(state->vref_reg);
> +
> +	return 0;
> +}
> +
> +static const struct spi_device_id mcp4922_id[] = {
> +	{"mcp4902", ID_MCP4902},
> +	{"mcp4912", ID_MCP4912},
> +	{"mcp4922", ID_MCP4922},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, mcp4922_id);
> +
> +static struct spi_driver mcp4922_driver = {
> +	.driver = {
> +		   .name = "mcp4922",
> +		   .owner = THIS_MODULE,
> +		   },
> +	.probe = mcp4922_probe,
> +	.remove = mcp4922_remove,
> +	.id_table = mcp4922_id,
> +};
> +module_spi_driver(mcp4922_driver);
> +
> +MODULE_AUTHOR("Michael Welling <mwelling@...e.org>");
> +MODULE_DESCRIPTION("Microchip MCP4902, MCP4912, MCP4922 DAC");
> +MODULE_LICENSE("GPL v2");
>

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