linux-kernel - RE: [PATCH 3/3] drivers: iio: adc: Rename the LTC249x iio device

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Date:   Mon, 29 Aug 2022 06:13:52 +0000
From:   "Regus, Ciprian" <Ciprian.Regus@...log.com>
To:     Lars-Peter Clausen <lars@...afoo.de>
CC:     "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/3] drivers: iio: adc: Rename the LTC249x iio device

Hi Lars,

Thanks for the review. I have one question before going further
with this patch.

> On 8/22/22 14:51, Ciprian Regus wrote:
> > Set the iio device's name based on the chip used.
> 
> While the change is correct it breaks the ABI. This needs a bit of a
> better explanation what is being done, why, what are the potential
> problems, why do we want to do it anyway.

The reason for this change is to make it easier to identify the device
(by having a generic name) when using an IIO client. The current name is
based on the i2c_client's kobj name, which has the format
"i2c_instance -i2c_address " (e.g. 1-0076). So, the renaming would allow
for interacting with the device without knowing which bus it's connected
to.

Also, as far as I can see, the IIO ABI states that the device's name is
"Typically a part number".

For the reason given, would this change be considered an
improvement, or is the ABI breaking too much of a drawback?
(in which case I'll just drop this patch)

Thanks,
Ciprian
> 
> >
> > Signed-off-by: Ciprian Regus <ciprian.regus@...log.com>
> > ---
> >   drivers/iio/adc/ltc2496.c      | 1 +
> >   drivers/iio/adc/ltc2497-core.c | 2 +-
> >   drivers/iio/adc/ltc2497.c      | 2 ++
> >   drivers/iio/adc/ltc2497.h      | 1 +
> >   4 files changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iio/adc/ltc2496.c b/drivers/iio/adc/ltc2496.c
> > index 98338104c24a..86470f49e8ca 100644
> > --- a/drivers/iio/adc/ltc2496.c
> > +++ b/drivers/iio/adc/ltc2496.c
> > @@ -89,6 +89,7 @@ static void ltc2496_remove(struct spi_device *spi)
> >
> >   static struct chip_info ltc2496_info = {
> >   	.resolution = 16,
> > +	.name = "ltc2496"
> >   };
> >
> >   static const struct of_device_id ltc2496_of_match[] = {
> > diff --git a/drivers/iio/adc/ltc2497-core.c b/drivers/iio/adc/ltc2497-core.c
> > index b2752399402c..6dd9ab601904 100644
> > --- a/drivers/iio/adc/ltc2497-core.c
> > +++ b/drivers/iio/adc/ltc2497-core.c
> > @@ -169,7 +169,7 @@ int ltc2497core_probe(struct device *dev, struct
> iio_dev *indio_dev)
> >   	struct ltc2497core_driverdata *ddata = iio_priv(indio_dev);
> >   	int ret;
> >
> > -	indio_dev->name = dev_name(dev);
> > +	indio_dev->name = ddata->chip_info->name;
> >   	indio_dev->info = &ltc2497core_info;
> >   	indio_dev->modes = INDIO_DIRECT_MODE;
> >   	indio_dev->channels = ltc2497core_channel;
> > diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c
> > index bb5e0d4301e2..a0aad71c8130 100644
> > --- a/drivers/iio/adc/ltc2497.c
> > +++ b/drivers/iio/adc/ltc2497.c
> > @@ -99,9 +99,11 @@ static int ltc2497_remove(struct i2c_client *client)
> >   static struct chip_info ltc2497_info[] = {
> >   	[TYPE_LTC2497] = {
> >   		.resolution = 16,
> > +		.name = "ltc2497"
> >   	},
> >   	[TYPE_LTC2499] = {
> >   		.resolution = 24,
> > +		.name = "ltc2499"
> >   	}
> >   };
> >
> > diff --git a/drivers/iio/adc/ltc2497.h b/drivers/iio/adc/ltc2497.h
> > index f4d939cfd48b..0e86e38248ee 100644
> > --- a/drivers/iio/adc/ltc2497.h
> > +++ b/drivers/iio/adc/ltc2497.h
> > @@ -12,6 +12,7 @@ enum chip_type {
> >
> >   struct chip_info {
> >   	u32 resolution;
> > +	char *name;
> >   };
> >
> >   struct ltc2497core_driverdata {
>