linux-kernel - Re: [PATCH next 1/4] iio: sca3000: cache SPI device ID in probe

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Message-ID: <20260131162807.137bb92a@jic23-huawei>
Date: Sat, 31 Jan 2026 16:28:07 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
Cc: David Lechner <dlechner@...libre.com>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>, Andrew Ijano
 <andrew.ijano@...il.com>, linux-iio@...r.kernel.org (open list:IIO
 SUBSYSTEM AND DRIVERS), linux-kernel@...r.kernel.org (open list),
 kernel-janitors@...r.kernel.org, Andy Shevchenko
 <andriy.shevchenko@...el.com>
Subject: Re: [PATCH next 1/4] iio: sca3000: cache SPI device ID in probe

On Fri, 30 Jan 2026 13:43:08 -0800
Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com> wrote:

> Store the spi_device_id at probe entry and reuse it for the name and
> chip info instead of calling spi_get_device_id() repeatedly.
> 
> Reuse the local dev pointer for resource managed helpers. While at it,
> reshuffle variable list in a reverse Christmas tree order.
> 
> No functional change intended.
> 
> Suggested-by: Andy Shevchenko <andriy.shevchenko@...el.com>
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
Hi Harshit,

A few comments inline but they are all about extra things to do rather
than really being comments on this patch which is fine as a starting point.

> ---
>  drivers/iio/accel/sca3000.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iio/accel/sca3000.c b/drivers/iio/accel/sca3000.c
> index 9ef4d6e27466..afe6ef61a53b 100644
> --- a/drivers/iio/accel/sca3000.c
> +++ b/drivers/iio/accel/sca3000.c
> @@ -1439,11 +1439,13 @@ static const struct iio_info sca3000_info = {
>  
>  static int sca3000_probe(struct spi_device *spi)
>  {
> -	int ret;
> +	const struct spi_device_id *id = spi_get_device_id(spi);

This is probably ok as an intermediate step, but ultimately we
shouldn't be using the spi_device_id at all.

id->driver_data should be a pointer to a named (not in array)
sca3000_chip_info structure and so should the data in the of_match_id
table etc.

Then we use spi_get_device_match_data() which prefers the of_device_id
table entry (which would needed adding).


> +	struct device *dev = &spi->dev;
>  	struct sca3000_state *st;
>  	struct iio_dev *indio_dev;
> +	int ret;
>  
> -	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
>  	if (!indio_dev)
>  		return -ENOMEM;
>  
> @@ -1451,10 +1453,9 @@ static int sca3000_probe(struct spi_device *spi)
>  	spi_set_drvdata(spi, indio_dev);
>  	st->us = spi;
>  	mutex_init(&st->lock);
> -	st->info = &sca3000_spi_chip_info_tbl[spi_get_device_id(spi)
> -					      ->driver_data];  
> +	st->info = &sca3000_spi_chip_info_tbl[id->driver_data];
>  
> -	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->name = id->name;

This also needs an update to make it get the name from within the
chip_info structure.  Whilst this works today it can be fragile
if we have dt compatibles that don't match exactly with the spi_device_id
table entries.

>  	indio_dev->info = &sca3000_info;
>  	if (st->info->temp_output) {
>  		indio_dev->channels = sca3000_channels_with_temp;
> @@ -1466,7 +1467,7 @@ static int sca3000_probe(struct spi_device *spi)
>  	}
>  	indio_dev->modes = INDIO_DIRECT_MODE;
>  
> -	ret = devm_iio_kfifo_buffer_setup(&spi->dev, indio_dev,
> +	ret = devm_iio_kfifo_buffer_setup(dev, indio_dev,
>  					  &sca3000_ring_setup_ops);
>  	if (ret)
>  		return ret;