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

Nicolas Ferre
2015-10-01T08:01:14Z

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.

Well, as I answered on the linux-pwm mailing-list (I was not in copy) here:
http://article.gmane.org/gmane.linux.pwm/2744
I wonder if it's not easier to fix the platforms and add the pwm tables...

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.

Bye,
--
Nicolas Ferre