Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

On 12.10.2015 18:19, Boris Brezillon wrote:

On Mon, 12 Oct 2015 17:19:35 +0300
Vladimir Zapolskiy [off-list ref] wrote:

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Thierry's patch makes sure that EPROBE_DEFER is not returned when the
PWM device definition is not found using in the PWM lookup tables or
the DT definition,

This is okay, but I'm interested in proper handling of cases other than
EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
and I'm attempting to avoid interfering with it here :)

I keep thinking we should fix all platforms using the ->pwm_id pdata
field to attach a PWM device to a PWM backlight instead of trying to
guess when falling back to the legacy API is acceptable...

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and in this case the pwm_bl code will fallback to
the legacy PWM API, which AFAICT is what you're trying to solve.

Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.

Before EPROBE_DEFER appeared on the scene the condition was
(IS_ERR(pb->pwm) && !pdev->dev.of_node).

So, the question is if my change requires any updates or not from your
point of view.

... but from a functional point of view your patch seems correct.

Sounds good, thank you for review.


Robert,

because you found a regression in the related area of code on a
platform, which uses legacy PWM API, could you please confirm that three
patches applied in a row don't break anything for you, the changes are:

* Nicolas' 68feaca0b1 ("backlight: pwm: Handle EPROBE_DEFER while
requesting the PWM")
* Thierry' https://lkml.org/lkml/2015/10/5/319
* and this one is the last in the series:
http://thread.gmane.org/gmane.linux.pwm/2813

--
With best wishes,
Vladimir