Re: [PATCH] Revert "backlight: pwm: Handle EPROBE_DEFER while requesting the PWM"

Robert Jarzmik
2015-10-01T17:45:01Z

Nicolas Ferre <nicolas.ferre@atmel.com> writes:

> Le 30/09/2015 21:29, Robert Jarzmik a écrit :
>> Robert Jarzmik <robert.jarzmik@free.fr> writes:
>>
>>> This reverts commit 68feaca0b13e453aa14ee064c1736202b48b342f.
>>> This commit breaks legacy platforms, for which :
>>> (a) no pwm table is added (legacy platforms)
>>> (b) in this case, in pwm_get(), pmw_lookup_list is empty, and therefore
>>> chosen == NULL, and therefore pwm_get() returns NULL, and pwm_get()
>>> returns -EPROBE_DEFER
>>> (c) as a consequence, this code is unreachable in pwm_bl.c :
>>> if (IS_ERR(pb->pwm)) {
>>> ret = PTR_ERR(pb->pwm);
>>> dev_info(&pdev->dev, "%s:%d(): %d\n", __func__, __LINE__, ret);
>>> if (ret == -EPROBE_DEFER)
>>> goto err_alloc;
>>>
>>> dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>>> pb->legacy = true;
>>> pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
>>>
>>> As this code is unreachable, all legacy platforms relying on pwm_id are
>>> broken, amongst which pxa have been tested as broken.
>>>
>>> Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
>> Thierry, would you have a look please ?
>> As I said before, all legacy platform relying on pwm_id are broken. I'd like to
>> be sure this lands in the next -rc series.
>
> Otherwise, Boris proposed this fix:
> 8<-----------------------------------------------------------
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index eff379b..00483d4 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -273,15 +273,15 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> if (IS_ERR(pb->pwm)) {
> ret = PTR_ERR(pb->pwm);
> - if (ret == -EPROBE_DEFER)
> - goto err_alloc;
>
> dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
> pb->legacy = true;
> pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
> if (IS_ERR(pb->pwm)) {
> dev_err(&pdev->dev, "unable to request legacy PWM\n");
> - ret = PTR_ERR(pb->pwm);
> + if (ret != -EPROBE_DEFER)
> + ret = PTR_ERR(pb->pwm);
> +
> goto err_alloc;
> }
> }
>
> which is not tested and may add an extra non-valid error log.
Now it is tested, and it works correctly AFAICS.

So could you or Borris post this patch, with :
Fixes: 68feaca0b13e ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>

That would be a good replacement for the revert. Maybe stable tree should be
joined too ...

Cheers.

--
Robert