Re: [PATCH RFC] media: radio: handle timeouts

From: Hans Verkuil
Date: Mon Feb 16 2015 - 06:19:40 EST


Hi Nicholas,

On 02/05/2015 09:56 AM, Nicholas Mc Guire wrote:
> Add handling for timeout case.
>
> Signed-off-by: Nicholas Mc Guire <hofrat@xxxxxxxxx>
> ---
> Some error state/error information seems be get lost int the current code.
> (line-numbers are from 3.19.0-rc7.
>
> Assume that on line 827 core->write succeeds but the following
> wait_for_completion_timeout times out and the radio->irq_received condition
> is not satisfied resulting in goto out;
>
> 827 r = core->write(core, WL1273_TUNER_MODE_SET, TUNER_MODE_AUTO_SEEK);
> 828 if (r)
> 829 goto out;
> 830
> 831 wait_for_completion_timeout(&radio->busy, msecs_to_jiffies(1000));
> 832 if (!(radio->irq_received & WL1273_BL_EVENT))
> 833 goto out;
>
>
> A similar situation is at line 955 - 859 where a tiemout could occure
> and the reported value would be the success value from core->write.
>
> 852 reinit_completion(&radio->busy);
> 853 dev_dbg(radio->dev, "%s: BUSY\n", __func__);
> 854
> 855 r = core->write(core, WL1273_TUNER_MODE_SET, TUNER_MODE_AUTO_SEEK);
> 856 if (r)
> 857 goto out;
> 858
> 859 wait_for_completion_timeout(&radio->busy, msecs_to_jiffies(1000)
>
> the problem is that the value of r now is the "success" value from core->write
> and any timeout and/or failure to detect the expected interrupt is not
> reported in
>
> 860 out:
> 861 dev_dbg(radio->dev, "%s: Err: %d\n", __func__, r);
> 862 return r;
>
> Should the wait_for_completion_timeout not report the timeout event by setting
> r to -ETIMEOUT ? respectively use if (!(radio->irq_received & WL1273_BL_EVENT))
> to check and set -ETIMEOUT there ?
>
> Comparing this with wl1273_fm_set_tx_freq - the below patch might be suitable
> way to handle timeout - but this needs a review by someone who knows the
> details of the driver - so this is really just a guess.

While I am certainly not an expert, I agree that the current situation is bad.

I'm taking your patch as-is, since returning a proper error here seems to make
much more sense.

Regards,

Hans

>
> Patch was only compile tested with x86_64_defconfig + CONFIG_MEDIA_SUPPORT=m
> CONFIG_MEDIA_CAMERA_SUPPORT=y, CONFIG_V4L_PLATFORM_DRIVERS=y,
> CONFIG_MEDIA_RADIO_SUPPORT=y, RADIO_ADAPTER=y, CONFIG_RADIO_WL1273=m
>
> Patch is against 3.19.0-rc7 (localversion-next is -next-20150204)
>
> drivers/media/radio/radio-wl1273.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/radio/radio-wl1273.c b/drivers/media/radio/radio-wl1273.c
> index 571c7f6..6830523 100644
> --- a/drivers/media/radio/radio-wl1273.c
> +++ b/drivers/media/radio/radio-wl1273.c
> @@ -828,9 +828,12 @@ static int wl1273_fm_set_seek(struct wl1273_device *radio,
> if (r)
> goto out;
>
> + /* wait for the FR IRQ */
> wait_for_completion_timeout(&radio->busy, msecs_to_jiffies(1000));
> - if (!(radio->irq_received & WL1273_BL_EVENT))
> + if (!(radio->irq_received & WL1273_BL_EVENT)) {
> + r = -ETIMEDOUT;
> goto out;
> + }
>
> radio->irq_received &= ~WL1273_BL_EVENT;
>
> @@ -856,7 +859,9 @@ static int wl1273_fm_set_seek(struct wl1273_device *radio,
> if (r)
> goto out;
>
> - wait_for_completion_timeout(&radio->busy, msecs_to_jiffies(1000));
> + /* wait for the FR IRQ */
> + if (!wait_for_completion_timeout(&radio->busy, msecs_to_jiffies(1000)))
> + r = -ETIMEDOUT;
> out:
> dev_dbg(radio->dev, "%s: Err: %d\n", __func__, r);
> return r;
>

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