linux-kernel - RE: [PATCH 10/16] iio: adc: max1027: Prevent single channel accesses during buffer reads

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Date:   Fri, 20 Aug 2021 07:20:53 +0000
From:   "Sa, Nuno" <Nuno.Sa@...log.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>
CC:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 10/16] iio: adc: max1027: Prevent single channel accesses
 during buffer reads



> -----Original Message-----
> From: Miquel Raynal <miquel.raynal@...tlin.com>
> Sent: Wednesday, August 18, 2021 1:12 PM
> To: Jonathan Cameron <jic23@...nel.org>; Lars-Peter Clausen
> <lars@...afoo.de>
> Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>; linux-
> iio@...r.kernel.org; linux-kernel@...r.kernel.org; Miquel Raynal
> <miquel.raynal@...tlin.com>
> Subject: [PATCH 10/16] iio: adc: max1027: Prevent single channel
> accesses during buffer reads
> 
> [External]
> 
> When hardware buffers are enabled (the cnvst pin being the trigger),
> one
> should not mess with the device state by requesting a single channel
> read. Prevent it with a iio_buffer_enabled() check.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> ---
>  drivers/iio/adc/max1027.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
> index 223c9e4abd86..83526f3d7d3a 100644
> --- a/drivers/iio/adc/max1027.c
> +++ b/drivers/iio/adc/max1027.c
> @@ -335,6 +335,8 @@ static int max1027_read_raw(struct iio_dev
> *indio_dev,
> 
>  	switch (mask) {
>  	case IIO_CHAN_INFO_RAW:
> +		if (iio_buffer_enabled(indio_dev))
> +			return -EBUSY;

I guess 'iio_device_claim_direct_mode()' would be a better option
here? There's nothing preventing this check to pass and then, concurrently
someone enables the buffer...

- Nuno Sá
>  		ret = max1027_read_single_value(indio_dev, chan,
> val);
>  		break;
>  	case IIO_CHAN_INFO_SCALE:
> --
> 2.27.0