linux-kernel - Re: [PATCH 2/2] misc: hx8837: add a HiMax HX8837 display controller driver

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Date:   Tue, 18 Dec 2018 16:28:05 +0100
From:   Lubomir Rintel <lkundrak@...sk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] misc: hx8837: add a HiMax HX8837 display controller
 driver

On Tue, 2018-11-27 at 08:41 +0100, Greg Kroah-Hartman wrote:
> On Mon, Nov 12, 2018 at 03:39:29AM +0100, Lubomir Rintel wrote:
> > HiMax HX8837 is a display controller used on OLPC platforms. It controls
> > backlight and is able to capture and freeze a frame when the LCD controller
> > (and the rest of the plaform) is powered off.
> > 
> > This driver is based on the same code as drivers/staging/olpc_dcon.
> > I modernized it to use managed GPIO, device-tree bindings, sysfs attribtue
> > groups, essentially fixing the staging driver's TODO.
> 
> You are creating custom sysfs files, with no Documentation/ABI/ update
> for us to know what those files are or how they are used :(
> 
> Why do you need custom sysfs files in the first place?  Isn't there
> already an api for this type of device in the kernel?

I am actually not sure. I certainly didn't find anything similar.

I've later discovered that this should perhaps be a DRM encoder driver,
because it sits between the LCDC and the panel; I'm submitting an
updated RFC version to the dri list.

Perhaps the color swizzling and frame freezing functionality that's
exposed via sysfs in this version could be exposed as a DRI property
instead.

> 
> thanks,
> 
> greg k-h

Lubo