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Date: Tue, 22 Sep 2015 19:22:39 +0100
From: Jonathan Cameron <jic23@...23.retrosnub.co.uk>
To: Peter Rosin <peda@...ator.liu.se>, linux-iio@...r.kernel.org
CC: Peter Rosin <peda@...ntia.se>, Crt Mori <cmo@...exis.com>,
Daniel Baluta <daniel.baluta@...il.com>,
Andreas Dannenberg <dannenberg@...com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jonathan Cameron <jic23@...nel.org>,
Hartmut Knaack <knaack.h@....de>,
Lars-Peter Clausen <lars@...afoo.de>,
Peter Meerwald <pmeerw@...erw.net>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] iio: mcp4531: Driver for Microchip digital potentiometers
On 22 September 2015 16:36:49 BST, Peter Rosin <peda@...ator.liu.se> wrote:
>From: Peter Rosin <peda@...ntia.se>
>
>Add support for Microchip digital potentiometers and rheostats
> MCP4531, MCP4532, MCP4551, MCP4552
> MCP4631, MCP4632, MCP4651, MCP4652
>
>These are either single (45xx) or dual (46xx) wipers with either
>129 (4x3x) or 257 (4x5x) steps, and configured either as
>potentiometers (4xx1) or rheostats (4xx2). They all use i2c
>client addresses of the 0101xxx form.
>
>Datasheet: http://www.microchip.com/downloads/en/DeviceDoc/22096b.pdf
>
>Signed-off-by: Peter Rosin <peda@...ntia.se>
Mostly fine though I think you may have gone a bit too much for conciseness over
clarity. Also the scale appears known so should be exposed to userspace.
>---
> MAINTAINERS | 6 ++
> drivers/iio/Kconfig | 1 +
> drivers/iio/Makefile | 1 +
> drivers/iio/potentiometer/Kconfig | 20 ++++
> drivers/iio/potentiometer/Makefile | 6 ++
>drivers/iio/potentiometer/mcp4531.c | 196
>+++++++++++++++++++++++++++++++++++
> 6 files changed, 230 insertions(+)
> create mode 100644 drivers/iio/potentiometer/Kconfig
> create mode 100644 drivers/iio/potentiometer/Makefile
> create mode 100644 drivers/iio/potentiometer/mcp4531.c
>
>diff --git a/MAINTAINERS b/MAINTAINERS
>index b60e2b2369d2..27862156c7a7 100644
>--- a/MAINTAINERS
>+++ b/MAINTAINERS
>@@ -6600,6 +6600,12 @@ W: http://linuxtv.org
> S: Maintained
> F: drivers/media/radio/radio-maxiradio*
>
>+MCP4531 MICROCHIP DIGITAL POTENTIOMETER DRIVER
>+M: Peter Rosin <peda@...ntia.se>
>+L: linux-iio@...r.kernel.org
>+S: Maintained
>+F: drivers/iio/potentiometer/mcp4531.c
>+
> MEDIA DRIVERS FOR RENESAS - VSP1
> M: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> L: linux-media@...r.kernel.org
>diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
>index 4011effe4c05..7cc87f322655 100644
>--- a/drivers/iio/Kconfig
>+++ b/drivers/iio/Kconfig
>@@ -73,6 +73,7 @@ source "drivers/iio/orientation/Kconfig"
> if IIO_TRIGGER
> source "drivers/iio/trigger/Kconfig"
> endif #IIO_TRIGGER
>+source "drivers/iio/potentiometer/Kconfig"
> source "drivers/iio/pressure/Kconfig"
> source "drivers/iio/proximity/Kconfig"
> source "drivers/iio/temperature/Kconfig"
>diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
>index 698afc2d17ce..121c814e366b 100644
>--- a/drivers/iio/Makefile
>+++ b/drivers/iio/Makefile
>@@ -23,6 +23,7 @@ obj-y += imu/
> obj-y += light/
> obj-y += magnetometer/
> obj-y += orientation/
>+obj-y += potentiometer/
> obj-y += pressure/
> obj-y += proximity/
> obj-y += temperature/
>diff --git a/drivers/iio/potentiometer/Kconfig
>b/drivers/iio/potentiometer/Kconfig
>new file mode 100644
>index 000000000000..fd75db73e582
>--- /dev/null
>+++ b/drivers/iio/potentiometer/Kconfig
>@@ -0,0 +1,20 @@
>+#
>+# Potentiometer drivers
>+#
>+# When adding new entries keep the list in alphabetical order
>+
>+menu "Digital potentiometers"
>+
>+config MCP4531
>+ tristate "Microchip MCP45xx/MCP46xx Digital Potentiometer driver"
>+ depends on I2C
>+ help
>+ Say yes here to build support for the Microchip
>+ MCP4531, MCP4532, MCP4551, MCP4552,
>+ MCP4631, MCP4632, MCP4651, MCP4652
>+ digital potentiomenter chips.
>+
>+ To compile this driver as a module, choose M here: the
>+ module will be called mcp4531.
>+
>+endmenu
>diff --git a/drivers/iio/potentiometer/Makefile
>b/drivers/iio/potentiometer/Makefile
>new file mode 100644
>index 000000000000..8afe49227012
>--- /dev/null
>+++ b/drivers/iio/potentiometer/Makefile
>@@ -0,0 +1,6 @@
>+#
>+# Makefile for industrial I/O potentiometer drivers
>+#
>+
>+# When adding new entries keep the list in alphabetical order
>+obj-$(CONFIG_MCP4531) += mcp4531.o
>diff --git a/drivers/iio/potentiometer/mcp4531.c
>b/drivers/iio/potentiometer/mcp4531.c
>new file mode 100644
>index 000000000000..04faf56dabe0
>--- /dev/null
>+++ b/drivers/iio/potentiometer/mcp4531.c
>@@ -0,0 +1,196 @@
>+/*
>+ * Industrial I/O driver for Microchip digital potentiometers
>+ * Copyright (c) 2015 Axentia Technologies AB
>+ * Author: Peter Rosin <peda@...ntia.se>
>+ *
>+ * Datasheet:
>http://www.microchip.com/downloads/en/DeviceDoc/22096b.pdf
>+ *
>+ * DEVID #Wipers #Positions Resistor Opts (kOhm) i2c address
>+ * mcp4531 1 129 5, 10, 50, 100 010111x
>+ * mcp4532 1 129 5, 10, 50, 100 01011xx
>+ * mcp4551 1 257 5, 10, 50, 100 010111x
>+ * mcp4552 1 257 5, 10, 50, 100 01011xx
>+ * mcp4631 2 129 5, 10, 50, 100 0101xxx
>+ * mcp4632 2 129 5, 10, 50, 100 01011xx
>+ * mcp4651 2 257 5, 10, 50, 100 0101xxx
>+ * mcp4652 2 257 5, 10, 50, 100 01011xx
>+ *
>+ * 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.
>+ */
>+
>+#include <linux/module.h>
>+#include <linux/i2c.h>
>+#include <linux/err.h>
>+
>+#include <linux/iio/iio.h>
>+
>+#define MCP4531_CONF(wipers, max_pos, uid) \
>+ ((((wipers) & 0xf) << 10) | \
>+ (((max_pos) & 0xf) << 6) | \
>+ ((uid) & 0x3f))
This strike me as harder to read than it need be. I think I would be clearer done
By setting dev_id to an index into an array to static const structs with the various
parts explicitly brought out as fields.
Preferably assigned with c99 syntax for really easy reading :)
>+
>+#define MCP4531_UID(conf) ((conf) & 0x3f)
>+#define MCP4531_MAX_POS(conf) (((conf) >> 6) & 0xf)
>+#define MCP4531_WIPERS(conf) (((conf) >> 10) & 0xf)
>+
>+#define MCP4531_WRITE (0 << 2)
>+#define MCP4531_INCR (1 << 2)
>+#define MCP4531_DECR (2 << 2)
>+#define MCP4531_READ (3 << 2)
>+
>+#define MCP4531_WIPER_SHIFT (4)
>+
>+enum mcp4531_devid {
>+ MCP4531_ID = MCP4531_CONF(1, 7, 0),
>+ MCP4532_ID = MCP4531_CONF(1, 7, 1),
>+ MCP4551_ID = MCP4531_CONF(1, 8, 2),
>+ MCP4552_ID = MCP4531_CONF(1, 8, 3),
>+ MCP4631_ID = MCP4531_CONF(2, 7, 4),
>+ MCP4632_ID = MCP4531_CONF(2, 7, 5),
>+ MCP4651_ID = MCP4531_CONF(2, 8, 6),
>+ MCP4652_ID = MCP4531_CONF(2, 8, 7),
>+};
>+
>+struct mcp4531_data {
>+ struct i2c_client *client;
>+ unsigned int max_pos;
>+ unsigned long devid;
>+};
>+
>+#define MCP4531_CHANNEL(ch) { \
>+ .type = IIO_RESISTANCE, \
>+ .indexed = 1, \
>+ .output = 1, \
>+ .channel = (ch), \
>+ .address = (ch) << MCP4531_WIPER_SHIFT, \
Why not drop specifying address and use channel with the shift applied at call site?
>+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
>+}
>+
>+static const struct iio_chan_spec mcp4531_channels[] = {
>+ MCP4531_CHANNEL(0),
>+ MCP4531_CHANNEL(1),
>+};
>+
>+static int mcp4531_get_value(struct iio_dev *indio_dev,
>+ int address, int *val)
>+{
>+ struct mcp4531_data *data = iio_priv(indio_dev);
>+ s32 ret;
>+
>+ ret = i2c_smbus_read_word_swapped(data->client,
>+ MCP4531_READ | address);
>+ if (ret < 0)
>+ return ret;
>+ *val = ret;
>+ return 0;
>+}
>+
>+static int mcp4531_set_value(struct iio_dev *indio_dev,
>+ int address, int val)
>+{
>+ struct mcp4531_data *data = iio_priv(indio_dev);
>+
>+ if (val >= data->max_pos || val < 0)
>+ return -EINVAL;
>+
>+ return i2c_smbus_write_byte_data(data->client,
>+ MCP4531_WRITE | address | (val >> 8),
>+ val & 0xff);
>+}
As each of these wrappers is so brief and only used once I would favour just merging them in where called.
>+
>+static int mcp4531_read_raw(struct iio_dev *indio_dev,
>+ struct iio_chan_spec const *chan,
>+ int *val, int *val2, long mask)
>+{
>+ int err;
>+
>+ switch (mask) {
>+ case IIO_CHAN_INFO_RAW:
>+ err = mcp4531_get_value(indio_dev, chan->address, val);
>+ if (err < 0)
>+ return err;
>+ return IIO_VAL_INT;
>+ }
No scale known? Be nice to relate to real world values. I gather this may need
platform data of some type (can't open data sheet on phone for some reason)
>+
>+ return -EINVAL;
>+}
>+
>+static int mcp4531_write_raw(struct iio_dev *indio_dev,
>+ struct iio_chan_spec const *chan,
>+ int val, int val2, long mask)
>+{
>+ switch (mask) {
>+ case IIO_CHAN_INFO_RAW:
>+ return mcp4531_set_value(indio_dev, chan->address, val);
>+ }
>+
>+ return -EINVAL;
>+}
>+
>+static const struct iio_info mcp4531_info = {
>+ .read_raw = mcp4531_read_raw,
>+ .write_raw = mcp4531_write_raw,
>+ .driver_module = THIS_MODULE,
>+};
>+
>+static int mcp4531_probe(struct i2c_client *client,
>+ const struct i2c_device_id *id)
>+{
>+ struct device *dev = &client->dev;
>+ unsigned long devid = id->driver_data;
>+ struct mcp4531_data *data;
>+ struct iio_dev *indio_dev;
>+
>+ if (!i2c_check_functionality(client->adapter,
>+ I2C_FUNC_SMBUS_WORD_DATA)) {
>+ dev_err(dev, "SMBUS Word Data not supported\n");
>+ return -EIO;
>+ }
>+
>+ indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
>+ if (!indio_dev)
>+ return -ENOMEM;
>+ data = iio_priv(indio_dev);
>+ i2c_set_clientdata(client, indio_dev);
>+ data->client = client;
>+ data->devid = devid;
>+
>+ data->max_pos = (1 << MCP4531_MAX_POS(devid)) + 1;
Derive at use site rather than here.
>+
>+ indio_dev->dev.parent = dev;
>+ indio_dev->info = &mcp4531_info;
>+ indio_dev->channels = mcp4531_channels;
>+ indio_dev->num_channels = MCP4531_WIPERS(devid);
>+ indio_dev->name = client->name;
>+
>+ return devm_iio_device_register(dev, indio_dev);
>+}
>+
>+static const struct i2c_device_id mcp4531_id[] = {
>+ { "mcp4531", MCP4531_ID },
>+ { "mcp4532", MCP4532_ID },
>+ { "mcp4551", MCP4551_ID },
>+ { "mcp4552", MCP4552_ID },
>+ { "mcp4631", MCP4631_ID },
>+ { "mcp4632", MCP4632_ID },
>+ { "mcp4651", MCP4651_ID },
>+ { "mcp4652", MCP4652_ID },
>+ {}
>+};
>+MODULE_DEVICE_TABLE(i2c, mcp4531_id);
>+
>+static struct i2c_driver mcp4531_driver = {
>+ .driver = {
>+ .name = "mcp4531",
>+ },
>+ .probe = mcp4531_probe,
>+ .id_table = mcp4531_id,
>+};
>+
>+module_i2c_driver(mcp4531_driver);
>+
>+MODULE_AUTHOR("Peter Rosin <peda@...ntia.se>");
>+MODULE_DESCRIPTION("MCP4531 digital potentiometer");
>+MODULE_LICENSE("GPL");
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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