linux-kernel - Re: [PATCH 4/4] leds: lm3532: Introduce the lm3532 LED driver

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Date:   Thu, 28 Mar 2019 22:04:37 +0100
From:   Sebastian Reichel <sre@...nel.org>
To:     Dan Murphy <dmurphy@...com>
Cc:     Tony Lindgren <tony@...mide.com>, robh+dt@...nel.org,
        jacek.anaszewski@...il.com, pavel@....cz, lee.jones@...aro.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-leds@...r.kernel.org
Subject: Re: [PATCH 4/4] leds: lm3532: Introduce the lm3532 LED driver

Hi,

On Mon, Mar 25, 2019 at 11:01:18AM -0500, Dan Murphy wrote:
> On 3/25/19 9:54 AM, Tony Lindgren wrote:
> > * Dan Murphy <dmurphy@...com> [190325 12:36]:
> >> On 3/22/19 5:16 PM, Tony Lindgren wrote:
> >>> I can control the backlight brightness just fine via /sys, and
> >>> backlight shows up as the trigger in /sys/class/leds/lm3532:backlight,
> >>> but /sys/class/backlight is empty and looks like drm can't find it.
> >>>
> >>> Do I need to enable some additional driver(s) to get this to work
> >>> with the drm driver?
> >>>
> >>
> >> Can you dump or point to the defconfig?
> > 
> > This is just with the omap2plus_defconfig as in the droid4-pending-v5.0
> > test branch below [0]. That branch has Sebastian's drm patches. The
> > branch also has the older ti-lmu patches that I reverted for testing
> > before applying your new series and enabling it in .config.
> > 
> > The drm driver (drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c) just
> > does:
> > 
> > backlight = of_parse_phandle(node, "backlight", 0);
> > ...
> > 
> > That should still work the same, right?
> 
> Yes it should still work the same.
> I did not change the node name.
> So the DRM driver should find the node.

This will not work, since the next line tries to get it as a
backlight device, but it's an LED device instead:

of_find_backlight_by_node(backlight);

I suppose the backlight device could be instantiated on top
of the LED device somehow.

(sorry for slow responses; I'm quite busy right now)

-- Sebastian

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