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From: Jonathan Cameron <jic23@kernel.org>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>,
	linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Nuno Sa <Nuno.Sa@analog.com>
Subject: Re: [PATCH v2 11/16] iio: adc: max1027: Prevent single channel accesses during buffer reads
Date: Sun, 5 Sep 2021 16:38:04 +0100	[thread overview]
Message-ID: <20210905163804.67fca556@jic23-huawei> (raw)
In-Reply-To: <20210902211437.503623-12-miquel.raynal@bootlin.com>

On Thu,  2 Sep 2021 23:14:32 +0200
Miquel Raynal <miquel.raynal@bootlin.com> wrote:

> 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.
> 
> There is already a iio_buffer_enabled() check in *_read_single_value()
> to merely prevent this situation but the check is inconsistent since
> buffers can be enabled after the if clause anyway. Instead, use the core
> mutex by calling iio_device_claim/release_direct_mode().
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> ---
>  drivers/iio/adc/max1027.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
> index f4cb5c75604b..57f62ea2d7aa 100644
> --- a/drivers/iio/adc/max1027.c
> +++ b/drivers/iio/adc/max1027.c
> @@ -296,10 +296,9 @@ static int max1027_read_single_value(struct iio_dev *indio_dev,
>  	int ret;
>  	struct max1027_state *st = iio_priv(indio_dev);
>  
> -	if (iio_buffer_enabled(indio_dev)) {
> -		dev_warn(&indio_dev->dev, "trigger mode already enabled");
> -		return -EBUSY;
> -	}
> +	ret = iio_device_claim_direct_mode(indio_dev);
> +	if (ret)
> +		return ret;

>  
>  	/* Configure conversion register with the requested chan */
>  	st->reg = MAX1027_CONV_REG | MAX1027_CHAN(chan->channel) |
> @@ -325,6 +324,8 @@ static int max1027_read_single_value(struct iio_dev *indio_dev,
>  	if (ret < 0)
>  		return ret;

Must also be released in error paths.  Treat it like a lock (there is one
internally) so to avoid permanent deadlock we must release it even if things
are going wrong

>  
> +	iio_device_release_direct_mode(indio_dev);
> +
>  	*val = be16_to_cpu(st->buffer[0]);
>  
>  	return IIO_VAL_INT;


  reply	other threads:[~2021-09-05 15:34 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-02 21:14 [PATCH v2 00/16] Bring external triggers support to MAX1027-like ADCs Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 01/16] iio: adc: max1027: Fix style Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 02/16] iio: adc: max1027: Drop extra warning message Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 03/16] iio: adc: max1027: Drop useless debug messages Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 04/16] iio: adc: max1027: Avoid device managed allocators for DMA purposes Miquel Raynal
2021-09-05 15:26   ` Jonathan Cameron
2021-09-02 21:14 ` [PATCH v2 05/16] iio: adc: max1027: Minimize the number of converted channels Miquel Raynal
2021-09-05 15:34   ` Jonathan Cameron
2021-09-15  9:46     ` Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 06/16] iio: adc: max1027: Rename a helper Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 07/16] iio: adc: max1027: Create a helper to enable/disable the cnvst trigger Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 08/16] iio: adc: max1027: Simplify the _set_trigger_state() helper Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 09/16] iio: adc: max1027: Ensure a default cnvst trigger configuration Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 10/16] iio: adc: max1027: Create a helper to configure the channels to scan Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 11/16] iio: adc: max1027: Prevent single channel accesses during buffer reads Miquel Raynal
2021-09-05 15:38   ` Jonathan Cameron [this message]
2021-09-02 21:14 ` [PATCH v2 12/16] iio: adc: max1027: Separate the IRQ handler from the read logic Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 13/16] iio: adc: max1027: Introduce an end of conversion helper Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 14/16] iio: adc: max1027: Don't just sleep when the EOC interrupt is available Miquel Raynal
2021-09-06  9:38   ` Sa, Nuno
2021-09-15  9:55     ` Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 15/16] iio: adc: max1027: Add support for external triggers Miquel Raynal
2021-09-05 16:10   ` Jonathan Cameron
2021-09-06  9:53     ` Sa, Nuno
2021-09-15 15:45       ` Miquel Raynal
2021-09-18 17:39         ` Jonathan Cameron
2021-09-20 10:47           ` Miquel Raynal
2021-09-15 10:18     ` Miquel Raynal
2021-09-18 17:13       ` Jonathan Cameron
2021-09-20  8:37         ` Miquel Raynal
2021-09-20 17:43           ` Jonathan Cameron
2021-09-21  8:11             ` Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 16/16] iio: adc: max1027: Don't reject external triggers when there is no IRQ Miquel Raynal

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