Re: [PATCH 2/2] iio: chemical: add atlas-ezo-sensor initial support

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 10 May 2020 17:29:41 -0700
Matt Ranostay <matt.ranostay@konsulko.com> wrote:

> On Sun, May 10, 2020 at 4:03 PM Matt Ranostay
> <matt.ranostay@konsulko.com> wrote:
> >
> > On Sun, May 10, 2020 at 2:00 AM Jonathan Cameron <jic23@kernel.org> wrote:  
> > >
> > > On Fri, 8 May 2020 10:49:41 -0700
> > > Matt Ranostay <matt.ranostay@konsulko.com> wrote:
> > >  
> > > > On Fri, May 8, 2020 at 5:39 AM Jonathan Cameron
> > > > <Jonathan.Cameron@huawei.com> wrote:  
> > > > >
> > > > > On Tue, 5 May 2020 21:22:00 -0700
> > > > > Matt Ranostay <matt.ranostay@konsulko.com> wrote:
> > > > >  
> > > > > > On Sun, May 3, 2020 at 3:17 AM Jonathan Cameron <jic23@kernel.org> wrote:  
> > > > > > >
> > > > > > > On Tue, 28 Apr 2020 08:41:07 +0300
> > > > > > > Matt Ranostay <matt.ranostay@konsulko.com> wrote:
> > > > > > >  
> > > > > > > > Add driver for Atlas EZO line of sensors with initial support for
> > > > > > > > CO2 the sensor. This is effectively ASCII strings proxied over I2C
> > > > > > > > due to these series of sensors being by default UART.
> > > > > > > >
> > > > > > > > Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>  
> > > > > > >
> > > > > > > A few things inline - including a dive into a bit of the i2c subsystem
> > > > > > > that's been there for a few years, but never used ;)
> > > > > > >
> > > > > > > Jonathan
> > > > > > >  
> > > > > > > > ---
> > > > > > > >  drivers/iio/chemical/Kconfig            |  11 ++
> > > > > > > >  drivers/iio/chemical/Makefile           |   1 +
> > > > > > > >  drivers/iio/chemical/atlas-ezo-sensor.c | 173 ++++++++++++++++++++++++
> > > > > > > >  3 files changed, 185 insertions(+)
> > > > > > > >  create mode 100644 drivers/iio/chemical/atlas-ezo-sensor.c
> > > > > > > >
> > > > > > > > diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
> > > > > > > > index a7e65a59bf42..7f21afd73b1c 100644
> > > > > > > > --- a/drivers/iio/chemical/Kconfig
> > > > > > > > +++ b/drivers/iio/chemical/Kconfig
> > > > > > > > @@ -22,6 +22,17 @@ config ATLAS_PH_SENSOR
> > > > > > > >         To compile this driver as module, choose M here: the
> > > > > > > >         module will be called atlas-ph-sensor.
> > > > > > > >
> > > > > > > > +config ATLAS_EZO_SENSOR
> > > > > > > > +     tristate "Atlas Scientific EZO sensors"
> > > > > > > > +     depends on I2C
> > > > > > > > +     help
> > > > > > > > +       Say Y here to build I2C interface support for the following
> > > > > > > > +       Atlas Scientific EZO sensors
> > > > > > > > +         * CO2 EZO Sensor
> > > > > > > > +
> > > > > > > > +       To compile this driver as module, choose M here: the
> > > > > > > > +       module will be called atlas-ezo-sensor.
> > > > > > > > +
> > > > > > > >  config BME680
> > > > > > > >       tristate "Bosch Sensortec BME680 sensor driver"
> > > > > > > >       depends on (I2C || SPI)
> > > > > > > > diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
> > > > > > > > index 33d3a595dda9..aba4167db745 100644
> > > > > > > > --- a/drivers/iio/chemical/Makefile
> > > > > > > > +++ b/drivers/iio/chemical/Makefile
> > > > > > > > @@ -5,6 +5,7 @@
> > > > > > > >
> > > > > > > >  # When adding new entries keep the list in alphabetical order
> > > > > > > >  obj-$(CONFIG_ATLAS_PH_SENSOR)        += atlas-sensor.o
> > > > > > > > +obj-$(CONFIG_ATLAS_EZO_SENSOR)       += atlas-ezo-sensor.o
> > > > > > > >  obj-$(CONFIG_BME680) += bme680_core.o
> > > > > > > >  obj-$(CONFIG_BME680_I2C) += bme680_i2c.o
> > > > > > > >  obj-$(CONFIG_BME680_SPI) += bme680_spi.o
> > > > > > > > diff --git a/drivers/iio/chemical/atlas-ezo-sensor.c b/drivers/iio/chemical/atlas-ezo-sensor.c
> > > > > > > > new file mode 100644
> > > > > > > > index 000000000000..1f972f525a46
> > > > > > > > --- /dev/null
> > > > > > > > +++ b/drivers/iio/chemical/atlas-ezo-sensor.c
> > > > > > > > @@ -0,0 +1,173 @@
> > > > > > > > +// SPDX-License-Identifier: GPL-2.0+
> > > > > > > > +/*
> > > > > > > > + * atlas-ezo-sensor.c - Support for Atlas Scientific EZO sensors
> > > > > > > > + *
> > > > > > > > + * Copyright (C) 2020 Konsulko Group
> > > > > > > > + * Author: Matt Ranostay <matt.ranostay@konsulko.com>
> > > > > > > > + */
> > > > > > > > +
> > > > > > > > +#include <linux/module.h>
> > > > > > > > +#include <linux/init.h>
> > > > > > > > +#include <linux/delay.h>
> > > > > > > > +#include <linux/mutex.h>
> > > > > > > > +#include <linux/err.h>
> > > > > > > > +#include <linux/i2c.h>
> > > > > > > > +#include <linux/of_device.h>
> > > > > > > > +#include <linux/iio/iio.h>
> > > > > > > > +
> > > > > > > > +#define ATLAS_EZO_DRV_NAME           "atlas-ezo-sensor"
> > > > > > > > +#define ATLAS_CO2_INT_TIME_IN_MS     950
> > > > > > > > +
> > > > > > > > +enum {
> > > > > > > > +     ATLAS_CO2_EZO,
> > > > > > > > +};
> > > > > > > > +
> > > > > > > > +struct atlas_ezo_device {
> > > > > > > > +     const struct iio_chan_spec *channels;
> > > > > > > > +     int num_channels;
> > > > > > > > +     int delay;
> > > > > > > > +};
> > > > > > > > +
> > > > > > > > +struct atlas_ezo_data {
> > > > > > > > +     struct i2c_client *client;
> > > > > > > > +     struct atlas_ezo_device *chip;  
> > > > > > >
> > > > > > > const?  Seems like it's always a pointer to a constant structure.
> > > > > > >  
> > > > > > > > +     struct mutex lock;  
> > > > > > >
> > > > > > > Locks should 'always' have a comment to say what their scope is.
> > > > > > > Even when it appears obvious ;)
> > > > > > >  
> > > > > > > > +     u8 buffer[8];
> > > > > > > > +};
> > > > > > > > +
> > > > > > > > +static const struct iio_chan_spec atlas_co2_ezo_channels[] = {
> > > > > > > > +     {
> > > > > > > > +             .type = IIO_CONCENTRATION,
> > > > > > > > +             .modified = 1,
> > > > > > > > +             .channel2 = IIO_MOD_CO2,
> > > > > > > > +             .info_mask_separate =
> > > > > > > > +                     BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> > > > > > > > +             .scan_index = 0,
> > > > > > > > +             .scan_type = {
> > > > > > > > +                     .sign = 'u',
> > > > > > > > +                     .realbits = 32,
> > > > > > > > +                     .storagebits = 32,
> > > > > > > > +                     .endianness = IIO_CPU,
> > > > > > > > +             },
> > > > > > > > +     },
> > > > > > > > +};
> > > > > > > > +
> > > > > > > > +static struct atlas_ezo_device atlas_ezo_devices[] = {  
> > > > > > >
> > > > > > > const?
> > > > > > >  
> > > > > > > > +     [ATLAS_CO2_EZO] = {
> > > > > > > > +             .channels = atlas_co2_ezo_channels,
> > > > > > > > +             .num_channels = 1,
> > > > > > > > +             .delay = ATLAS_CO2_INT_TIME_IN_MS,
> > > > > > > > +     },
> > > > > > > > +};
> > > > > > > > +
> > > > > > > > +static int atlas_ezo_read_raw(struct iio_dev *indio_dev,
> > > > > > > > +                       struct iio_chan_spec const *chan,
> > > > > > > > +                       int *val, int *val2, long mask)
> > > > > > > > +{
> > > > > > > > +     struct atlas_ezo_data *data = iio_priv(indio_dev);
> > > > > > > > +     struct i2c_client *client = data->client;
> > > > > > > > +     int ret = 0;
> > > > > > > > +
> > > > > > > > +     if (chan->type != IIO_CONCENTRATION)
> > > > > > > > +             return -EINVAL;
> > > > > > > > +
> > > > > > > > +     switch (mask) {
> > > > > > > > +     case IIO_CHAN_INFO_RAW: {
> > > > > > > > +             int tmp;
> > > > > > > > +
> > > > > > > > +             mutex_lock(&data->lock);
> > > > > > > > +
> > > > > > > > +             tmp = i2c_smbus_write_byte(client, 'R');
> > > > > > > > +
> > > > > > > > +             if (tmp < 0) {
> > > > > > > > +                     mutex_unlock(&data->lock);
> > > > > > > > +                     return tmp;
> > > > > > > > +             }
> > > > > > > > +
> > > > > > > > +             msleep(data->chip->delay);
> > > > > > > > +
> > > > > > > > +             tmp = i2c_master_recv(client, data->buffer, sizeof(data->buffer));
> > > > > > > > +
> > > > > > > > +             // Confirm response code is 1 for success  
> > > > > > >
> > > > > > > Comment syntax /* */
> > > > > > >  
> > > > > > > > +             if (tmp < 0 || data->buffer[0] != 1) {
> > > > > > > > +                     mutex_unlock(&data->lock);
> > > > > > > > +                     return -EBUSY;
> > > > > > > > +             }
> > > > > > > > +
> > > > > > > > +             ret = kstrtol(data->buffer + 1, 10, (long *) val);  
> > > > > > >
> > > > > > > Use a local variable rather than casting like that which could in theory
> > > > > > > be unsafe.
> > > > > > >  
> > > > > > > > +
> > > > > > > > +             mutex_unlock(&data->lock);
> > > > > > > > +
> > > > > > > > +             return ret ? ret : IIO_VAL_INT;
> > > > > > > > +     }
> > > > > > > > +     case IIO_CHAN_INFO_SCALE:
> > > > > > > > +             *val = 1;
> > > > > > > > +             *val2 = 10000; /* 0.0001 */
> > > > > > > > +             return IIO_VAL_FRACTIONAL;  
> > > > > > >
> > > > > > > Could use VAL_INT_PLUS_MICRO to reduce the maths needed for
> > > > > > > a constant case like we have here where that representation
> > > > > > > is just as easy to read as this one.
> > > > > > >  
> > > > > > > > +     }
> > > > > > > > +  
> > > > > > >
> > > > > > > Can only get here in invalid path. So return -EINVAL and don't
> > > > > > > initialize ret above.
> > > > > > >  
> > > > > > > > +     return ret;
> > > > > > > > +}
> > > > > > > > +
> > > > > > > > +static const struct iio_info atlas_info = {
> > > > > > > > +     .read_raw = atlas_ezo_read_raw,
> > > > > > > > +};
> > > > > > > > +
> > > > > > > > +static const struct i2c_device_id atlas_ezo_id[] = {
> > > > > > > > +     { "atlas-co2-ezo", ATLAS_CO2_EZO },
> > > > > > > > +     {}
> > > > > > > > +};
> > > > > > > > +MODULE_DEVICE_TABLE(i2c, atlas_ezo_id);
> > > > > > > > +
> > > > > > > > +static const struct of_device_id atlas_ezo_dt_ids[] = {
> > > > > > > > +     { .compatible = "atlas,co2-ezo", .data = (void *)ATLAS_CO2_EZO, },
> > > > > > > > +     {}
> > > > > > > > +};
> > > > > > > > +MODULE_DEVICE_TABLE(of, atlas_ezo_dt_ids);
> > > > > > > > +
> > > > > > > > +static int atlas_ezo_probe(struct i2c_client *client,
> > > > > > > > +                    const struct i2c_device_id *id)
> > > > > > > > +{
> > > > > > > > +     struct atlas_ezo_data *data;
> > > > > > > > +     struct atlas_ezo_device *chip;
> > > > > > > > +     const struct of_device_id *of_id;
> > > > > > > > +     struct iio_dev *indio_dev;
> > > > > > > > +
> > > > > > > > +     indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> > > > > > > > +     if (!indio_dev)
> > > > > > > > +             return -ENOMEM;
> > > > > > > > +
> > > > > > > > +     of_id = of_match_device(atlas_dt_ids, &client->dev);
> > > > > > > > +     if (!of_id)
> > > > > > > > +             chip = &atlas_ezo_devices[id->driver_data];  
> > > > > > >
> > > > > > > Given we are supposed to be transitioning away (slowly) from
> > > > > > > probe to probe_new, we shouldn't really be using id to do anything
> > > > > > > in here (directly anyway)
> > > > > > >
> > > > > > > Looking at i2c_of_match_device, there is some magic to match
> > > > > > > if we have initialized through the sysfs interface, so use that
> > > > > > > instead.
> > > > > > >
> > > > > > > https://elixir.bootlin.com/linux/latest/source/drivers/i2c/i2c-core-of.c#L224
> > > > > > >
> > > > > > > I 'think' that takes care of the case where we haven't instantiated
> > > > > > > via device tree.
> > > > > > >
> > > > > > > Interestingly it's a very little used function. But, the original discussion
> > > > > > > included a patch doing pretty much what I'm suggesting here:
> > > > > > >
> > > > > > > https://lore.kernel.org/patchwork/patch/728984/  
> > > > > >
> > > > > > Looks good but what about ACPI systems like x86? Which now my UP^2 is
> > > > > > my main development system now.  
> > > > >
> > > > > I'm not sure what you mean?  ACPI based probing doesn't use the old
> > > > > I2C ID table anyway.
> > > > >
> > > > > So three ways to work with them:
> > > > >
> > > > > 1) the sysfs interface as above.
> > > > > 2) actual ACPI IDs and bindings but those need specific support in
> > > > >    the driver.
> > > > > 3) PRP0001 ID and the magic device tree bindings.  You would need
> > > > >    to use the generic firmware calls, but you aren't currently doing
> > > > >    that.. It will be an issue for the above function but seems like
> > > > >    it would make sense to have a similar wrapper with the string based
> > > > >    fallback for that as well.
> > > > >
> > > > > So how are you instantiating this on your ACPI based board?  
> > > >
> > > > Manually using the new_device entry in /sys/bus/i2c/*
> > > >
> > > > # echo "atlas-co2-ezo 0x69" > new_device  
> > >
> > > That should be fine without the separate old style table.
> > > new_device_store
> > > https://elixir.bootlin.com/linux/latest/source/drivers/i2c/i2c-core-base.c#L1026
> > >
> > > calls
> > > i2c_new_client_device
> > > https://elixir.bootlin.com/linux/latest/source/drivers/i2c/i2c-core-base.c#L732
> > >
> > > which calls device_register
> > >
> > > That will result in device_add -> ... via  a long chain... -> __device_attach_driver  
> > > -> drv->bus->match which for the i2c subsystem is:  
> > > i2c_device_match
> > >
> > > which will call i2c_of_match_device if there is an of_match_table
> > > (before it tries the old style table)
> > >
> > > That function is the one which will happily match the name without the vendor id.
> > >
> > > Thus you should still be able to use that method without needing to register
> > > the old style table.  
> >
> > Ah so still keep the old style table but just don't need to register it?
> >  
> 
> Doesn't seem to work as expected that way.. could debug further but
> will send v2 for review in the meantime

Interesting.  I wonder what I missed... I didn't have any convenient
setup to hand to test on so was just based on reading the code.
Would be good to figure this out at somepoint - perhaps I'll fire
something up soon to look at it if no one else does.

Thanks,

Jonathan

> 
> - Matt
> 
> > - Matt
> >  
> > >
> > > At least that's how I believe it is suppose to work.  Maybe I'm missing something!
> > >
> > > Jonathan
> > >  
> > > >
> > > > Thanks,
> > > >
> > > > Matt
> > > >  
> > > > >
> > > > > Jonathan
> > > > >  
> > > > > >
> > > > > > Thanks,
> > > > > >
> > > > > > Matt
> > > > > >  
> > > > > > >
> > > > > > >  
> > > > > > > > +     else
> > > > > > > > +             chip = &atlas_ezo_devices[(unsigned long)of_id->data];
> > > > > > > > +
> > > > > > > > +     indio_dev->info = &atlas_info;
> > > > > > > > +     indio_dev->name = ATLAS_EZO_DRV_NAME;
> > > > > > > > +     indio_dev->channels = chip->channels;
> > > > > > > > +     indio_dev->num_channels = chip->num_channels;
> > > > > > > > +     indio_dev->modes = INDIO_DIRECT_MODE;
> > > > > > > > +     indio_dev->dev.parent = &client->dev;
> > > > > > > > +
> > > > > > > > +     data = iio_priv(indio_dev);
> > > > > > > > +     data->client = client;
> > > > > > > > +     data->chip = chip;
> > > > > > > > +     mutex_init(&data->lock);
> > > > > > > > +
> > > > > > > > +     return devm_iio_device_register(&client->dev, indio_dev);
> > > > > > > > +};
> > > > > > > > +
> > > > > > > > +static struct i2c_driver atlas_ezo_driver = {
> > > > > > > > +     .driver = {
> > > > > > > > +             .name   = ATLAS_EZO_DRV_NAME,
> > > > > > > > +             .of_match_table = atlas_ezo_dt_ids,
> > > > > > > > +     },
> > > > > > > > +     .probe          = atlas_ezo_probe,
> > > > > > > > +     .id_table       = atlas_ezo_id,
> > > > > > > > +};
> > > > > > > > +module_i2c_driver(atlas_ezo_driver);
> > > > > > > > +
> > > > > > > > +MODULE_AUTHOR("Matt Ranostay <matt.ranostay@konsulko.com>");
> > > > > > > > +MODULE_DESCRIPTION("Atlas Scientific EZO sensors");
> > > > > > > > +MODULE_LICENSE("GPL");  
> > > > > > >  
> > > > >
> > > > >  
> > >