Re: [PATCH] iio: magnetometer: Add support for PNI RM3100 9-axis magnetometer

From: Jonathan Cameron
Date: Sat Sep 29 2018 - 08:50:52 EST

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In reply to: Song Qiang: "Re: [PATCH] iio: magnetometer: Add support for PNI RM3100 9-axis magnetometer"
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On Mon, 24 Sep 2018 22:37:14 +0800
Song Qiang <songqiang1304521@xxxxxxxxx> wrote:

> On Sat, Sep 22, 2018 at 11:14:09AM +0100, Jonathan Cameron wrote:
> > On Thu, 20 Sep 2018 21:13:40 +0800
> > Song Qiang <songqiang1304521@xxxxxxxxx> wrote:
> >
> > > PNI RM3100 magnetometer is a high resolution, large signal immunity
> > > magnetometer, composed of 3 single sensors and a processing chip.
> > > PNI is currently not in the vendors list, so this is also adding it.
> > >
> > > Following functions are available:
> > > - Single-shot measurement from
> > > /sys/bus/iio/devices/iio:deviceX/in_magn_{axis}_raw
> > > - Triggerd buffer measurement.
> > > - Both i2c and spi interface are supported.
> > > - Both interrupt and polling measurement is supported, depands on if
> > > the 'interrupts' in DT is declared.
> > >
> > > Signed-off-by: Song Qiang <songqiang1304521@xxxxxxxxx>
> > Hi Song,
>
> ...
>
> > > + if (ret < 0)
> > > + return ret;
> > > +
> > > + /* 3sec more wait time. */
> > > + ret = regmap_read(data->regmap, RM_REG_TMRC, &tmp);
> > > + data->conversion_time = rm3100_samp_rates[tmp-RM_TMRC_OFFSET][2] + 3000;
> > > +
> > > + /* Starting all channels' conversion. */
> > > + ret = regmap_write(regmap, RM_REG_CMM,
> > > + RM_CMM_PMX | RM_CMM_PMY | RM_CMM_PMZ | RM_CMM_START);
> > > + if (ret < 0)
> > > + return ret;
> > > +
> > > + return devm_iio_device_register(dev, indio_dev);
> > Nope. Can't do this without having a race condition. You need
> > to ensure the userspace and in kernel interfaces are removed 'before'.
> > you do that RM_REG_CMM write in remove.
> >
> > One option is to use devm_add_action to add a custom unwind function
> > to the automatic handling. The other is to not use devm for everything
> > after the write above and do the device_unregister manually.
> >
>
> Hi Jonathan,
>
> I considered the both options you mentioned, and I was going to use the
> manual way. But then something came to my mind, what if there is another
> devm_* operation needs care, what if more. I checked devm_add_action in
> source code, and it says that this function only adds unwinding handlers.
> I guess this method was designed for this situation, and if we have
> already used devm_ in our code, it's better to use devm_add_action for
> cleanup, is that right?

It can provide a very clean solution. Be careful though. You do need
to make sure to handle a failure of this function itself.

Jonathan

>
> yours,
> Song Qiang
>
> > > +}
> > > +EXPORT_SYMBOL(rm3100_common_probe);
> > > +
> > > +int rm3100_common_remove(struct device *dev)
> > > +{
> > > + struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > > + struct rm3100_data *data = iio_priv(indio_dev);
> > > + struct regmap *regmap = data->regmap;
> > > +
> > > + regmap_write(regmap, RM_REG_CMM, 0x00);
> > > +
> > > + return 0;
> > No real point in returning int if you are always going to put 0 in
> > in it. Should probably check the regmap_write though and output
> > a log message if it fails (as no other way of telling).
> >
> > > +}
> > > +EXPORT_SYMBOL(rm3100_common_remove);
> > > +
> > > +MODULE_AUTHOR("Song Qiang <songqiang1304521@xxxxxxxxx>");
> > > +MODULE_DESCRIPTION("PNI RM3100 9-axis magnetometer i2c driver");
> > > +MODULE_LICENSE("GPL v2");
> > > diff --git a/drivers/iio/magnetometer/rm3100-i2c.c b/drivers/iio/magnetometer/rm3100-i2c.c
> > > new file mode 100644
> > > index 000000000000..b50dc5b1b30b
> > > --- /dev/null
> > > +++ b/drivers/iio/magnetometer/rm3100-i2c.c
> > > @@ -0,0 +1,66 @@
> > > +// SPDX-License-Identifier: GPL-2.0+
> > > +/*
> > > + * Support for PNI RM3100 9-axis geomagnetic sensor a i2c bus.
> > > + *
> > > + * Copyright (C) 2018 Song Qiang <songqiang1304521@xxxxxxxxx>
> > > + *
> > > + * User Manual available at
> > > + * <https://www.pnicorp.com/download/rm3100-user-manual/>
> > > + *
> > > + * i2c slave address 0x20 + SA1 << 1 + SA0.
> > > + */
> > > +
> > > +#include <linux/i2c.h>
> > > +
> > > +#include "rm3100.h"
> > > +
> > > +static const struct regmap_config rm3100_regmap_config = {
> > > + .reg_bits = 8,
> > This indenting seems an extra tab on conventional choice...
> > > + .val_bits = 8,
> > > +
> > > + .rd_table = &rm3100_readable_table,
> > > + .wr_table = &rm3100_writable_table,
> > > + .volatile_table = &rm3100_volatile_table,
> > > +
> > > + .cache_type = REGCACHE_RBTREE,
> > > +};
> > > +
> > > +static int rm3100_probe(struct i2c_client *client)
> > > +{
> > > + struct regmap *regmap;
> > > +
> > > + if (!i2c_check_functionality(client->adapter,
> > > + I2C_FUNC_SMBUS_READ_I2C_BLOCK | I2C_FUNC_SMBUS_BYTE_DATA))
> > > + return -EOPNOTSUPP;
> > > +
> > > + regmap = devm_regmap_init_i2c(client, &rm3100_regmap_config);
> > > + if (IS_ERR(regmap))
> > > + return PTR_ERR(regmap);
> > > +
> > > + return rm3100_common_probe(&client->dev, regmap, client->irq);
> > > +}
> > > +
> > > +static int rm3100_remove(struct i2c_client *client)
> > > +{
> > > + return rm3100_common_remove(&client->dev);
> > > +}
> > > +
> > > +static const struct of_device_id rm3100_dt_match[] = {
> > > + { .compatible = "pni,rm3100-i2c", },
> > > + { }
> > > +};
> > > +MODULE_DEVICE_TABLE(of, rm3100_dt_match);
> > > +
> > > +static struct i2c_driver rm3100_driver = {
> > > + .driver = {
> > > + .name = "rm3100-i2c",
> > > + .of_match_table = rm3100_dt_match,
> > > + },
> > > + .probe_new = rm3100_probe,
> > > + .remove = rm3100_remove,
> > > +};
> > > +module_i2c_driver(rm3100_driver);
> > > +
> > > +MODULE_AUTHOR("Song Qiang <songqiang1304521@xxxxxxxxx>");
> > > +MODULE_DESCRIPTION("PNI RM3100 9-axis magnetometer i2c driver");
> > > +MODULE_LICENSE("GPL v2");
> > > diff --git a/drivers/iio/magnetometer/rm3100-spi.c b/drivers/iio/magnetometer/rm3100-spi.c
> > > new file mode 100644
> > > index 000000000000..2c7dd9e3a1a2
> > > --- /dev/null
> > > +++ b/drivers/iio/magnetometer/rm3100-spi.c
> > > @@ -0,0 +1,72 @@
> > > +// SPDX-License-Identifier: GPL-2.0+
> > > +/*
> > > + * Support for PNI RM3100 9-axis geomagnetic sensor a spi bus.
> > > + *
> > > + * Copyright (C) 2018 Song Qiang <songqiang1304521@xxxxxxxxx>
> > > + *
> > > + * User Manual available at
> > > + * <https://www.pnicorp.com/download/rm3100-user-manual/>
> >
> > Probably only worth mentioning the manual in the main file.
> >
> > > + */
> > > +
> > > +#include <linux/spi/spi.h>
> > > +
> > > +#include "rm3100.h"
> > > +
> > > +static const struct regmap_config rm3100_regmap_config = {
> > > + .reg_bits = 8,
> > > + .val_bits = 8,
> > > +
> > > + .rd_table = &rm3100_readable_table,
> > > + .wr_table = &rm3100_writable_table,
> > > + .volatile_table = &rm3100_volatile_table,
> > > +
> > > + .read_flag_mask = 0x80,
> > > +
> > > + .cache_type = REGCACHE_RBTREE,
> > > +};
> > > +
> > > +static int rm3100_probe(struct spi_device *spi)
> > > +{
> > > + struct regmap *regmap;
> > > + int ret;
> > > +
> > > + /* Actually this device supports both mode 0 and mode 3. */
> > > + spi->mode = SPI_MODE_0;
> > > + /* data rates cannot exceeds 1Mbits. */
> > > + spi->max_speed_hz = 1000000;
> > > + spi->bits_per_word = 8;
> > > + ret = spi_setup(spi);
> > > + if (ret)
> > > + return ret;
> > > +
> > > + regmap = devm_regmap_init_spi(spi, &rm3100_regmap_config);
> > > + if (IS_ERR(regmap))
> > > + return PTR_ERR(regmap);
> > > +
> > > + return rm3100_common_probe(&spi->dev, regmap, spi->irq);
> > > +}
> > > +
> > > +static int rm3100_remove(struct spi_device *spi)
> > > +{
> > > + return rm3100_common_remove(&spi->dev);
> > > +}
> > > +
> > > +static const struct of_device_id rm3100_dt_match[] = {
> > > + { .compatible = "pni,rm3100-spi", },
> > > + { }
> > > +};
> > > +MODULE_DEVICE_TABLE(of, rm3100_dt_match);
> > > +
> > > +static struct spi_driver rm3100_driver = {
> > > + .driver = {
> > > + .name = "rm3100-spi",
> > > + .of_match_table = rm3100_dt_match,
> >
> > Indenting looks oddly deep...
> >
> > > + },
> > > + .probe = rm3100_probe,
> > > + .remove = rm3100_remove,
> > > +};
> > > +module_spi_driver(rm3100_driver);
> > > +
> > > +MODULE_AUTHOR("Song Qiang <songqiang1304521@xxxxxxxxx>");
> > > +MODULE_DESCRIPTION("PNI RM3100 9-axis magnetometer spi driver");
> > > +MODULE_LICENSE("GPL v2");
> > > diff --git a/drivers/iio/magnetometer/rm3100.h b/drivers/iio/magnetometer/rm3100.h
> > > new file mode 100644
> > > index 000000000000..5e30bc0f5149
> > > --- /dev/null
> > > +++ b/drivers/iio/magnetometer/rm3100.h
> > > @@ -0,0 +1,90 @@
> > > +/* SPDX-License-Identifier: GPL-2.0+ */
> > > +/*
> > > + * Header file for PNI RM3100 driver
> > > + *
> > > + * Copyright (C) 2018 Song Qiang <songqiang1304521@xxxxxxxxx>
> > > + */
> > > +
> > > +#ifndef RM3100_CORE_H
> > > +#define RM3100_CORE_H
> > > +
> > > +#include <linux/module.h>
> > > +#include <linux/regmap.h>
> >
> > What in here needs module.h? Push that down into the
> > individual c files. It's repetition but it si generally
> > good practice to include headers at as low a level as possible.
> >
> > > +
> > > +#define RM_REG_REV_ID 0x36
> > I would prefer RM3100 as the prefix.
> > > +
> > > +/* Cycle Count Registers MSBs and LSBs. */
> > Could probably give these slightly more human readable names?
> > RM3100_REG_CC_X_MSB
> >
> > Actually I doubt you use both of them in the driver anyway...
> > (just searched, nope you don't so drop the ones you don't
> > use and then the MSB, LSB definition probably not necessary).
> >
> > > +#define RM_REG_CCXM 0x04
> > > +#define RM_REG_CCXL 0x05
> > > +#define RM_REG_CCYM 0x06
> > > +#define RM_REG_CCYL 0x07
> > > +#define RM_REG_CCZM 0x08
> > > +#define RM_REG_CCZL 0x09
> > > +
> > > +/* Single Measurement Mode register. */
> > > +#define RM_REG_POLL 0x00
> > > +#define RM_POLL_PMX BIT(4)
> > > +#define RM_POLL_PMY BIT(5)
> > > +#define RM_POLL_PMZ BIT(6)
> > > +
> > > +/* Continues Measurement Mode register. */
> > > +#define RM_REG_CMM 0x01
> > > +#define RM_CMM_START BIT(0)
> > > +#define RM_CMM_DRDM BIT(2)
> > > +#define RM_CMM_PMX BIT(4)
> > > +#define RM_CMM_PMY BIT(5)
> > > +#define RM_CMM_PMZ BIT(6)
> > > +
> > > +/* TiMe Rate Configuration register. */
> > > +#define RM_REG_TMRC 0x0B
> > > +#define RM_TMRC_OFFSET 0x92
> > > +
> > > +/* Result Status register. */
> > > +#define RM_REG_STATUS 0x34
> > > +#define RM_STATUS_DRDY BIT(7)
> > > +
> > > +/* Measurement result registers. */
> > > +#define RM_REG_MX2 0x24
> >
> > You only use some of these. Not sure having defines for the
> > others is really helpful.
> >
> > > +#define RM_REG_MX1 0x25
> > > +#define RM_REG_MX0 0x26
> > > +#define RM_REG_MY2 0x27
> > > +#define RM_REG_MY1 0x28
> > > +#define RM_REG_MY0 0x29
> > > +#define RM_REG_MZ2 0x2a
> > > +#define RM_REG_MZ1 0x2b
> > > +#define RM_REG_MZ0 0x2c
> > > +
> > > +#define RM_REG_HSHAKE 0x35
> > > +
> > > +#define RM_W_REG_START RM_REG_POLL
> > > +#define RM_W_REG_END RM_REG_REV_ID
> > > +#define RM_R_REG_START RM_REG_POLL
> > > +#define RM_R_REG_END RM_REG_HSHAKE
> > > +#define RM_V_REG_START RM_REG_MX2
> > > +#define RM_V_REG_END RM_REG_HSHAKE
> > > +
> > > +/* Built-In Self Test reigister. */
> > > +#define RM_REG_BIST 0x33
> > > +
> > > +struct rm3100_data {
> > > + struct device *dev;
> > > + struct regmap *regmap;
> > > + struct completion measuring_done;
> > > + bool use_interrupt;
> > > +
> > > + int conversion_time;
> > > +
> > > + /* To protect consistency of every measurement and sampling
> >
> > /*
> > * To protect
> > */
> > (common format to most of the kernel other than those 'crazy' :)
> > people in net and a few other corners.
> >
> > > + * frequency change operations.
> > > + */
> > > + struct mutex lock;
> > > +};
> > > +
> > > +extern const struct regmap_access_table rm3100_readable_table;
> > > +extern const struct regmap_access_table rm3100_writable_table;
> > > +extern const struct regmap_access_table rm3100_volatile_table;
> > > +
> > > +int rm3100_common_probe(struct device *dev, struct regmap *regmap, int irq);
> > > +int rm3100_common_remove(struct device *dev);
> > > +
> > > +#endif /* RM3100_CORE_H */
> >

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In reply to: Song Qiang: "Re: [PATCH] iio: magnetometer: Add support for PNI RM3100 9-axis magnetometer"
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