linux-kernel - Re: [PATCH v2] iio: proximity: isl29501: fix buffered read on big-endian systems

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Message-ID: <20250724120329.671dc192@jic23-huawei>
Date: Thu, 24 Jul 2025 12:03:29 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: Nuno Sá <nuno.sa@...log.com>, Andy Shevchenko
 <andy@...nel.org>, Mathieu Othacehe <othacehe@....org>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, Jonathan Cameron
 <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v2] iio: proximity: isl29501: fix buffered read on
 big-endian systems

On Tue, 22 Jul 2025 15:54:21 -0500
David Lechner <dlechner@...libre.com> wrote:

> Fix passing a u32 value as a u16 buffer scan item. This works on little-
> endian systems, but not on big-endian systems.
> 
> A new local variable is introduced for getting the register value and
> the array is changed to a struct to make the data layout more explicit
> rather than just changing the type and having to recalculate the proper
> length needed for the timestamp.
> 
> Fixes: 1c28799257bc ("iio: light: isl29501: Add support for the ISL29501 ToF sensor.")
> Signed-off-by: David Lechner <dlechner@...libre.com>
ok. This probably is the best minimal fix but there is a bunch of other type
confusion around this in the driver (not as far as I can see actual bugs though).

Might be good to circle back and make the val parameter of isl29501_register_read()
a u16 as a follow up.

Applied to my temporary fixes-togreg-for-6.17 branch on iio.git and marked
for stable.

Thanks,

Jonathan



> ---
> Changes in v2:
> - Use u16 to match channel scan_type and introduce new local u32 variable
>   for getting the register value.
> - Reword subject and commit message since we now consider this a bug fix.
> - Fix not zero-initializing the new struct.
> - Link to v1: https://lore.kernel.org/r/20250711-iio-use-more-iio_declare_buffer_with_ts-7-v1-1-a3f253ac2e4a@baylibre.com
> ---
>  drivers/iio/proximity/isl29501.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/proximity/isl29501.c b/drivers/iio/proximity/isl29501.c
> index d1510fe2405088adc0998e28aa9f36e0186fafae..f69db6f2f380313b8444ee21399ee3a9faed6f04 100644
> --- a/drivers/iio/proximity/isl29501.c
> +++ b/drivers/iio/proximity/isl29501.c
> @@ -938,12 +938,18 @@ static irqreturn_t isl29501_trigger_handler(int irq, void *p)
>  	struct iio_dev *indio_dev = pf->indio_dev;
>  	struct isl29501_private *isl29501 = iio_priv(indio_dev);
>  	const unsigned long *active_mask = indio_dev->active_scan_mask;
> -	u32 buffer[4] __aligned(8) = {}; /* 1x16-bit + naturally aligned ts */
> -
> -	if (test_bit(ISL29501_DISTANCE_SCAN_INDEX, active_mask))
> -		isl29501_register_read(isl29501, REG_DISTANCE, buffer);
> +	u32 value;
> +	struct {
> +		u16 data;
> +		aligned_s64 ts;
> +	} scan = { };
> +
> +	if (test_bit(ISL29501_DISTANCE_SCAN_INDEX, active_mask)) {
> +		isl29501_register_read(isl29501, REG_DISTANCE, &value); 
> +		scan.data = value;
> +	}
>  
> -	iio_push_to_buffers_with_timestamp(indio_dev, buffer, pf->timestamp);
> +	iio_push_to_buffers_with_timestamp(indio_dev, &scan, pf->timestamp);
>  	iio_trigger_notify_done(indio_dev->trig);
>  
>  	return IRQ_HANDLED;
> 
> ---
> base-commit: cd2731444ee4e35db76f4fb587f12d327eec5446
> change-id: 20250711-iio-use-more-iio_declare_buffer_with_ts-7-880ddf1d3070
> 
> Best regards,