From mboxrd@z Thu Jan  1 00:00:00 1970
From: jeffy <jeffy.chen@rock-chips.com>
Date: Tue, 17 Oct 2017 08:13:55 +0000
Subject: Re: [RESEND PATCH v2 2/5] backlight: pwm_bl: Add device link for pwm_bl and pwm
Message-Id: <59E5BBC3.2020504@rock-chips.com>
List-Id: <linux-fbdev.vger.kernel.org>
References: <20171016100640.26575-1-jeffy.chen@rock-chips.com>
 <20171016100640.26575-3-jeffy.chen@rock-chips.com>
 <20171016235710.GA12188@google.com>
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To: Brian Norris <briannorris@chromium.org>
Cc: linux-pwm@vger.kernel.org, linux-fbdev@vger.kernel.org, Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>, linux-kernel@vger.kernel.org, dmitry.torokhov@gmail.com, rjw@rjwysocki.net, dianders@chromium.org, dri-devel@lists.freedesktop.org, tfiga@chromium.org, broonie@kernel.org, Jingoo Han <jingoohan1@gmail.com>, Thierry Reding <thierry.reding@gmail.com>, Daniel Thompson <daniel.thompson@linaro.org>, Lee Jones <lee.jones@linaro.org>

Hi Brian,

On 10/17/2017 07:57 AM, Brian Norris wrote:
> This is going to be a*lot*  of churn throughout the tree, if we expect
> all resource consumers to do this. I think we'd want some kind of
> agreement from the PM maintainers and (larger) subsystem owners before
> going down this route...
>
> And in the PWM case, pwm_get() already has the device pointer. Why can't
> we just instrument it instead?

according to pwm_bl driver, we may need to take care of pwm_request() too:

         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && 
!node) {
                 dev_err(&pdev->dev, "unable to request PWM, trying 
legacy API\n");
                 pb->legacy = true;
                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
         }

and maybe also *of_pwm_get...

maybe we can add a dummy pwm chip for those orphan pwms?
>
> Brian