linux-kernel - Re: [PATCH v2] iio: adc: ad7606_spi: add offload scan mask check

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Message-ID: <CAHp75VdtoxGu1qv7i6uhuPhAeVF7OUF3d5trxqcmupC+ZeAf0A@mail.gmail.com>
Date: Fri, 2 May 2025 21:21:49 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: Michael Hennerich <Michael.Hennerich@...log.com>, Jonathan Cameron <jic23@...nel.org>, 
	Nuno Sá <nuno.sa@...log.com>, 
	Andy Shevchenko <andy@...nel.org>, Angelo Dureghello <adureghello@...libre.com>, 
	Jonathan Cameron <Jonathan.Cameron@...wei.com>, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: adc: ad7606_spi: add offload scan mask check

On Fri, May 2, 2025 at 6:42 PM David Lechner <dlechner@...libre.com> wrote:
>
> Validate the scan mask when SPI offloading is being used.
>
> Since this family of ADCs is simultaneous sampling, there isn't a way
> to selectively disable channels when reading sample data. (Technically,
> AD7616 has a sequencer so could have some control, but that is for

so it could

> another day).
>
> For "regular" IIO triggered buffer reads, this isn't a problem and the
> IIO core will demux the data and ignore data from disabled channels.
> However, since SPI offloading is done completely in hardware, we don't
> have a way to do the same. So before this patch, if less than all
> channels were enabled, the data would be misplaced in the buffer.
>
> By adding a check in update_scan_mode, we can fail to enable the buffer
> instead of having bad data returned to userspace.

Reviewed-by: Andy Shevchenko <andy@...nel.org>

-- 
With Best Regards,
Andy Shevchenko