linux-kernel - Re: [PATCH 2/3] iio: adc: ad7887: convert driver to full DT probing

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Message-ID: <20201117160218.0000274b@Huawei.com>
Date:   Tue, 17 Nov 2020 16:02:18 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Alexandru Ardelean <ardeleanalex@...il.com>
CC:     Alexandru Ardelean <alexandru.ardelean@...log.com>,
        linux-iio <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        "Rob Herring" <robh+dt@...nel.org>,
        Vaishnav M A <vaishnav@...gleboard.org>,
        "Andy Shevchenko" <andy.shevchenko@...il.com>
Subject: Re: [PATCH 2/3] iio: adc: ad7887: convert driver to full DT probing

On Tue, 17 Nov 2020 17:03:06 +0200
Alexandru Ardelean <ardeleanalex@...il.com> wrote:

> On Tue, Nov 17, 2020 at 1:06 PM Jonathan Cameron
> <Jonathan.Cameron@...wei.com> wrote:
> >
> > On Tue, 17 Nov 2020 11:01:11 +0000
> > Jonathan Cameron <Jonathan.Cameron@...wei.com> wrote:
> >  
> > > On Tue, 17 Nov 2020 09:52:53 +0200
> > > Alexandru Ardelean <alexandru.ardelean@...log.com> wrote:
> > >  
> > > > This change removes the SPI device table, adds an OF device table instead.
> > > > This should also be usable for ACPI via PRP0001.
> > > >
> > > > This device is usually probed via device-tree, so it makes more sense to
> > > > use the OF device table.
> > > >
> > > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>  
> > > So, we've had a few cases of having to put the device_id table
> > > back again recently.
> > > https://lore.kernel.org/linux-iio/20201101152613.2c37581a@archlinux/
> > >
> > > They tend to be due to greybus doing it's probing in yet another fashion.
> > > So far they've been all i2c devices, but I kind of assume it does the same for spi.
> > > https://elixir.bootlin.com/linux/latest/source/drivers/staging/greybus/spilib.c#L437
> > >
> > > How device_get_match_data() plays with that I'm not sure. It probably
> > > doesn't right now given swnode doesn't have a device_get_match_data() callback.
> > >
> > > https://elixir.bootlin.com/linux/latest/source/drivers/base/swnode.c#L539
> > >
> > > So after all that I think I've argued myself around to thinking what you have
> > > here is fine.  If someone wants to support this via a swnode then they can
> > > figure out how to make that work.
> > >
> > > +CC Vaishnav and Andy for their input.
> > >
> > > Otherwise looks fine to me.  
> >
> > Having said that.... Why are we going through this dance for driver with
> > only one compatible?   Are there other parts on their way?
> > If not, perhaps we should just rip out the matching code entirely in
> > the interests of simplicity.  
> 
> So, this one has a bit of a funny story.
> There's an AD7888 which is similar in terms of registers but with more channels.
> Lars did a patch to support it on top of AD7887:
>     https://github.com/analogdevicesinc/linux/commits/iio-ad7888
> 
> We tried to order a part for this to test the changes, but we got a
> reply that it's obsolete.
> The website says it is still in production.
> So, I was confused about the answer we got. ¯\_(ツ)_/¯
> 
> In the meantime, I thought I'd take some of the cleanup value of Lars'
> work and do the cleanup only.
> We may still find that part somewhere and maybe add it, or maybe
> another one would come along.
> I don't know at this point. I'm mostly looking at some of my backlog
> stuff and trying to cleanup old stuff.
> 
> I'm fine to simplify the driver now and add the matching bits later.

Sounds good to me.

> 
> >
> > Jonathan
> >  
> > >
> > > Thanks,
> > >
> > > Jonathan
> > >
> > >  
> > > > ---
> > > >  drivers/iio/adc/ad7887.c | 23 +++++++++++++++--------
> > > >  1 file changed, 15 insertions(+), 8 deletions(-)
> > > >
> > > > diff --git a/drivers/iio/adc/ad7887.c b/drivers/iio/adc/ad7887.c
> > > > index 06f684c053a0..4f68a1b17ec8 100644
> > > > --- a/drivers/iio/adc/ad7887.c
> > > > +++ b/drivers/iio/adc/ad7887.c
> > > > @@ -40,6 +40,7 @@ enum ad7887_channels {
> > > >
> > > >  /**
> > > >   * struct ad7887_chip_info - chip specifc information
> > > > + * @name:          the name of the part
> > > >   * @int_vref_mv:   the internal reference voltage
> > > >   * @channels:              channels specification
> > > >   * @num_channels:  number of channels
> > > > @@ -47,6 +48,7 @@ enum ad7887_channels {
> > > >   * @num_dual_channels:     number of channels in dual mode
> > > >   */
> > > >  struct ad7887_chip_info {
> > > > +   const char                      *name;
> > > >     u16                             int_vref_mv;
> > > >     const struct iio_chan_spec      *channels;
> > > >     unsigned int                    num_channels;
> > > > @@ -218,6 +220,7 @@ static const struct ad7887_chip_info ad7887_chip_info_tbl[] = {
> > > >      * More devices added in future
> > > >      */
> > > >     [ID_AD7887] = {
> > > > +           .name = "ad7887",
> > > >             .channels = ad7887_channels,
> > > >             .num_channels = ARRAY_SIZE(ad7887_channels),
> > > >             .dual_channels = ad7887_dual_channels,
> > > > @@ -239,12 +242,17 @@ static void ad7887_reg_disable(void *data)
> > > >
> > > >  static int ad7887_probe(struct spi_device *spi)
> > > >  {
> > > > +   const struct ad7887_chip_info *info;
> > > >     struct ad7887_state *st;
> > > >     struct iio_dev *indio_dev;
> > > >     bool dual_mode;
> > > >     uint8_t mode;
> > > >     int ret;
> > > >
> > > > +   info = device_get_match_data(&spi->dev);
> > > > +   if (!info)
> > > > +           return -ENODEV;
> > > > +
> > > >     indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> > > >     if (indio_dev == NULL)
> > > >             return -ENOMEM;
> > > > @@ -269,13 +277,12 @@ static int ad7887_probe(struct spi_device *spi)
> > > >                     return ret;
> > > >     }
> > > >
> > > > -   st->chip_info =
> > > > -           &ad7887_chip_info_tbl[spi_get_device_id(spi)->driver_data];
> > > > +   st->chip_info = info;
> > > >
> > > >     spi_set_drvdata(spi, indio_dev);
> > > >     st->spi = spi;
> > > >
> > > > -   indio_dev->name = spi_get_device_id(spi)->name;
> > > > +   indio_dev->name = st->chip_info->name;
> > > >     indio_dev->info = &ad7887_info;
> > > >     indio_dev->modes = INDIO_DIRECT_MODE;
> > > >
> > > > @@ -336,18 +343,18 @@ static int ad7887_probe(struct spi_device *spi)
> > > >     return devm_iio_device_register(&spi->dev, indio_dev);
> > > >  }
> > > >
> > > > -static const struct spi_device_id ad7887_id[] = {
> > > > -   {"ad7887", ID_AD7887},
> > > > -   {}
> > > > +static const struct of_device_id ad7887_of_match[] = {
> > > > +   { .compatible = "adi,ad7887", .data = &ad7887_chip_info_tbl[ID_AD7887] },
> > > > +   { }
> > > >  };
> > > > -MODULE_DEVICE_TABLE(spi, ad7887_id);
> > > > +MODULE_DEVICE_TABLE(of, ad7887_of_match);
> > > >
> > > >  static struct spi_driver ad7887_driver = {
> > > >     .driver = {
> > > >             .name   = "ad7887",
> > > > +           .of_match_table = ad7887_of_match,
> > > >     },
> > > >     .probe          = ad7887_probe,
> > > > -   .id_table       = ad7887_id,
> > > >  };
> > > >  module_spi_driver(ad7887_driver);
> > > >  
> > >  
> >