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Date: Fri, 18 Feb 2022 12:32:28 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Jagath Jog J <jagathjog1996@...il.com>
Cc: lars@...afoo.de, andy.shevchenko@...il.com, sst@...zta.fm,
robh+dt@...nel.org, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/6] iio: potentiometer: Add support for Maxim DS3502
On Fri, 18 Feb 2022 09:50:37 +0530
Jagath Jog J <jagathjog1996@...il.com> wrote:
> The DS3502 is a 7-bit, nonvolatile digital potentiometer featuring
> an output voltage range of up to 15.5V.
> DS3502 support is implemented into existing DS1803 driver.
> Datasheet: https://datasheets.maximintegrated.com/en/ds/DS3502.pdf
>
> Signed-off-by: Jagath Jog J <jagathjog1996@...il.com>
Hi Jagath,
One suggestion from my review of v2. Instead of putting the enum
for type in the per chip type cfg structure, use a function pointer
and break out the device specific bits of the read_raw() into
separate functions accessed via that function pointer.
Thanks,
Jonathan
> ---
> drivers/iio/potentiometer/Kconfig | 6 ++--
> drivers/iio/potentiometer/ds1803.c | 46 ++++++++++++++++++++++++------
> 2 files changed, 41 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
> index 832df8da2bc6..79c524640196 100644
> --- a/drivers/iio/potentiometer/Kconfig
> +++ b/drivers/iio/potentiometer/Kconfig
> @@ -27,11 +27,11 @@ config AD5272
> module will be called ad5272.
>
> config DS1803
> - tristate "Maxim Integrated DS1803 Digital Potentiometer driver"
> + tristate "Maxim Integrated DS1803 and similar Digital Potentiometer driver"
> depends on I2C
> help
> - Say yes here to build support for the Maxim Integrated DS1803
> - digital potentiometer chip.
> + Say yes here to build support for the Maxim Integrated Devices DS1803 and
> + DS3502 digital potentiometer chip.
>
> To compile this driver as a module, choose M here: the
> module will be called ds1803.
> diff --git a/drivers/iio/potentiometer/ds1803.c b/drivers/iio/potentiometer/ds1803.c
> index ca28ad147402..ca903e9c2816 100644
> --- a/drivers/iio/potentiometer/ds1803.c
> +++ b/drivers/iio/potentiometer/ds1803.c
> @@ -1,12 +1,15 @@
> // SPDX-License-Identifier: GPL-2.0-only
> /*
> - * Maxim Integrated DS1803 digital potentiometer driver
> + * Maxim Integrated DS1803 and similar digital potentiometer driver
> * Copyright (c) 2016 Slawomir Stepien
> + * Copyright (c) 2022 Jagath Jog J
> *
> * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS1803.pdf
> + * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS3502.pdf
> *
> * DEVID #Wipers #Positions Resistor Opts (kOhm) i2c address
> * ds1803 2 256 10, 50, 100 0101xxx
> + * ds3502 1 128 10 01010xx
> */
>
> #include <linux/err.h>
> @@ -18,11 +21,13 @@
>
> #define DS1803_WIPER_0 0xA9
> #define DS1803_WIPER_1 0xAA
> +#define DS3502_WR_IVR 0x00
>
> enum ds1803_type {
> DS1803_010,
> DS1803_050,
> DS1803_100,
> + DS3502,
> };
>
> struct ds1803_cfg {
> @@ -36,6 +41,7 @@ struct ds1803_cfg {
> struct ds1803_data {
> struct i2c_client *client;
> const struct ds1803_cfg *cfg;
> + enum ds1803_type chip_type;
Hmm. I'm not that keen on this backwards reference (effectively).
Consider using a read() function pointer in here instead.
> };
>
> #define DS1803_CHANNEL(ch, addr) { \
> @@ -54,6 +60,10 @@ static const struct iio_chan_spec ds1803_channels[] = {
> DS1803_CHANNEL(1, DS1803_WIPER_1),
> };
>
> +static const struct iio_chan_spec ds3502_channels[] = {
> + DS1803_CHANNEL(0, DS3502_WR_IVR),
> +};
> +
> static const struct ds1803_cfg ds1803_cfg[] = {
> [DS1803_010] = { .wipers = 2, .avail = { 0, 1, 255 }, .kohms = 10,
> .channels = ds1803_channels,
> @@ -64,6 +74,9 @@ static const struct ds1803_cfg ds1803_cfg[] = {
> [DS1803_100] = { .wipers = 2, .avail = { 0, 1, 255 }, .kohms = 100,
> .channels = ds1803_channels,
> .num_channels = ARRAY_SIZE(ds1803_channels) },
> + [DS3502] = { .wipers = 1, .avail = { 0, 1, 127 }, .kohms = 10,
> + .channels = ds3502_channels,
> + .num_channels = ARRAY_SIZE(ds3502_channels) },
> };
>
> static int ds1803_read_raw(struct iio_dev *indio_dev,
> @@ -77,13 +90,26 @@ static int ds1803_read_raw(struct iio_dev *indio_dev,
>
> switch (mask) {
> case IIO_CHAN_INFO_RAW:
> - ret = i2c_master_recv(data->client, result,
> - indio_dev->num_channels);
> - if (ret < 0)
> - return ret;
> -
> - *val = result[pot];
> - return IIO_VAL_INT;
> + switch (data->chip_type) {
> + case DS1803_010:
> + case DS1803_050:
> + case DS1803_100:
This block can become
ret = data->read(indio_dev, chan, val);
or something along those lines and you can remove the switch statement
as it's a simple lookup.
> + ret = i2c_master_recv(data->client, result,
> + indio_dev->num_channels);
> + if (ret < 0)
> + return ret;
> + *val = result[pot];
> + return IIO_VAL_INT;
> + case DS3502:
> + ret = i2c_smbus_read_byte_data(data->client,
> + chan->address);
> + if (ret < 0)
> + return ret;
> + *val = ret;
> + return IIO_VAL_INT;
> + default:
> + return -EINVAL;
> + }
>
> case IIO_CHAN_INFO_SCALE:
> *val = 1000 * data->cfg->kohms;
> @@ -156,6 +182,7 @@ static int ds1803_probe(struct i2c_client *client, const struct i2c_device_id *i
> if (!data->cfg)
> data->cfg = &ds1803_cfg[id->driver_data];
>
> + data->chip_type = id->driver_data;
> indio_dev->info = &ds1803_info;
> indio_dev->channels = data->cfg->channels;
> indio_dev->num_channels = data->cfg->num_channels;
> @@ -168,6 +195,7 @@ static const struct of_device_id ds1803_dt_ids[] = {
> { .compatible = "maxim,ds1803-010", .data = &ds1803_cfg[DS1803_010] },
> { .compatible = "maxim,ds1803-050", .data = &ds1803_cfg[DS1803_050] },
> { .compatible = "maxim,ds1803-100", .data = &ds1803_cfg[DS1803_100] },
> + { .compatible = "maxim,ds3502", .data = &ds1803_cfg[DS3502] },
> {}
> };
> MODULE_DEVICE_TABLE(of, ds1803_dt_ids);
> @@ -176,6 +204,7 @@ static const struct i2c_device_id ds1803_id[] = {
> { "ds1803-010", DS1803_010 },
> { "ds1803-050", DS1803_050 },
> { "ds1803-100", DS1803_100 },
> + { "ds3502", DS3502 },
> {}
> };
> MODULE_DEVICE_TABLE(i2c, ds1803_id);
> @@ -192,5 +221,6 @@ static struct i2c_driver ds1803_driver = {
> module_i2c_driver(ds1803_driver);
>
> MODULE_AUTHOR("Slawomir Stepien <sst@...zta.fm>");
> +MODULE_AUTHOR("Jagath Jog J <jagathjog1996@...il.com>");
> MODULE_DESCRIPTION("DS1803 digital potentiometer");
> MODULE_LICENSE("GPL v2");
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