linux-kernel - Re: [PATCH 2/2] iio: inkern: add error case in iio_channel

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Message-ID: <504DAFF7.1070902@jic23.retrosnub.co.uk>
Date:	Mon, 10 Sep 2012 10:16:39 +0100
From:	Jonathan Cameron <jic23@...23.retrosnub.co.uk>
To:	"Kim, Milo" <Milo.Kim@...com>
CC:	Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] iio: inkern: add error case in iio_channel_get()

On 10/09/12 09:02, Kim, Milo wrote:
>   The datasheet name is defined in the IIO driver.
>   On the other hand, the adc_channel_label is configured in
>   the platform machine side.
>   If the datasheet name is not matched with any adc_channel_label,
>   the iio_channel_get() should be returned as error for preventing
>   using invalid IIO channel data.
>
>   Moreover, this patch detects NULL pointer dereference problem at early time.
>   In general, the IIO driver just accesses to any member of the iio_chan_spec
>   in own xxx_read_raw() function.
>   If the iio_chan_spec is invalid pointer, NULL dereference problem may occur
>   such like 'iio_chan_spec->channel' or 'iio_chan_spec->type'.
>   If the iio_channel_get() gets failed in the IIO consumer,
>   then no read_raw() operation proceeds.
I guess this is marginally cleaner, but either way it is up to the 
calling driver to check whether the call succeeded.
>
> Signed-off-by: Milo(Woogyom) Kim <milo.kim@...com>
> ---
>   drivers/iio/inkern.c |    6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index 1faa240..a5caf6b 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -136,11 +136,15 @@ struct iio_channel *iio_channel_get(const char *name, const char *channel_name)
>
>   	channel->indio_dev = c->indio_dev;
>
> -	if (c->map->adc_channel_label)
> +	if (c->map->adc_channel_label) {
>   		channel->channel =
>   			iio_chan_spec_from_name(channel->indio_dev,
>   						c->map->adc_channel_label);
>
> +		if (channel->channel == NULL)
> +			return ERR_PTR(-ENODEV);
> +	}
> +
>   	return channel;
>   }
>   EXPORT_SYMBOL_GPL(iio_channel_get);
>

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