linux-kernel - Re: [PATCH v2 5/5] drivers: iio: adc: Rename the LTC2499 iio device

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Date:   Sun, 4 Sep 2022 16:09:51 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Ciprian Regus <ciprian.regus@...log.com>
Cc:     <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 5/5] drivers: iio: adc: Rename the LTC2499 iio device

On Thu, 1 Sep 2022 15:17:00 +0300
Ciprian Regus <ciprian.regus@...log.com> wrote:

> Set the iio device's name based on the chip used for the
> LTC2499 only. The most common way for IIO clients to interact
> with a device is to address it based on it's name. By using
> the dev_name() function, the name will be set based on a
> i2c_client's kobj name, which has the format i2c_instance-i2c_address
> (1-0076 for example). This is not ideal, since it makes a
> requirement for userspace to have knowledge about the hardware
> connections of the device.
> 
> The name field is set to NULL for the LTC2497 and LTC2496, so
> that the old name can kept as it is, since changing it will
> result in an ABI breakage.
> 
> Signed-off-by: Ciprian Regus <ciprian.regus@...log.com>
Other than the issue with the split between patches 4 and 5 that
the robot found this looks good to me.

Jonathan

> ---
> changes in v2:
>  - updated the patch title (LTC249x -> LTC2499), since the name change only
>    affects the LTC2499.
>  - updated the commit description to better explain what is being done.
>  - only changed the iio_dev's name for the LTC2499.
>  - added a comment to explain difference in naming.
>  - added the const qualifier to the name field.
>  drivers/iio/adc/ltc2496.c      |  1 +
>  drivers/iio/adc/ltc2497-core.c | 10 +++++++++-
>  drivers/iio/adc/ltc2497.h      |  1 +
>  3 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/ltc2496.c b/drivers/iio/adc/ltc2496.c
> index bf89d5ae19af..2593fa4322eb 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 const struct ltc2497_chip_info ltc2496_info = {
>  	.resolution = 16,
> +	.name = NULL,
>  };
>  
>  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..f52d37af4d1f 100644
> --- a/drivers/iio/adc/ltc2497-core.c
> +++ b/drivers/iio/adc/ltc2497-core.c
> @@ -169,7 +169,15 @@ 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);
> +	/*
> +	 * Keep using dev_name() for the iio_dev's name on some of the parts,
> +	 * since updating it would result in a ABI breakage.
> +	 */
> +	if (ddata->chip_info->name)
> +		indio_dev->name = ddata->chip_info->name;
> +	else
> +		indio_dev->name = dev_name(dev);
> +
>  	indio_dev->info = &ltc2497core_info;
>  	indio_dev->modes = INDIO_DIRECT_MODE;
>  	indio_dev->channels = ltc2497core_channel;
> diff --git a/drivers/iio/adc/ltc2497.h b/drivers/iio/adc/ltc2497.h
> index 95f6a5f4d4a6..fd3dfd491060 100644
> --- a/drivers/iio/adc/ltc2497.h
> +++ b/drivers/iio/adc/ltc2497.h
> @@ -12,6 +12,7 @@ enum ltc2497_chip_type {
>  
>  struct ltc2497_chip_info {
>  	u32 resolution;
> +	const char *name;
>  };
>  
>  struct ltc2497core_driverdata {