linux-kernel - Re: [RESEND PATCH v2 2/5] backlight: pwm_bl: Add device link for pwm

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Date:   Tue, 17 Oct 2017 16:13:55 +0800
From:   jeffy <jeffy.chen@...k-chips.com>
To:     Brian Norris <briannorris@...omium.org>
CC:     linux-kernel@...r.kernel.org, dmitry.torokhov@...il.com,
        heiko@...ech.de, rjw@...ysocki.net, dianders@...omium.org,
        tfiga@...omium.org, broonie@...nel.org, seanpaul@...omium.org,
        linux-pwm@...r.kernel.org, linux-fbdev@...r.kernel.org,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        dri-devel@...ts.freedesktop.org, Jingoo Han <jingoohan1@...il.com>,
        Lee Jones <lee.jones@...aro.org>
Subject: Re: [RESEND PATCH v2 2/5] backlight: pwm_bl: Add device link for
 pwm_bl and pwm

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