Re: [PATCH 4/8] ARM: dts: sun8i: Add touchscreen node for sun8i-a23-gt90h

[Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

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On Mon, Aug 22, 2016 at 09:03:57PM +0200, Hans de Goede wrote:
> Hi,
> 
> On 22-08-16 20:30, Maxime Ripard wrote:
> >On Mon, Aug 08, 2016 at 09:43:14PM +0200, Hans de Goede wrote:
> >>The gt90h tablet has a gsl3675 touchscreen, add a dt node describing it.
> >>
> >>Signed-off-by: Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> >>---
> >> arch/arm/boot/dts/sun8i-a23-gt90h-v4.dts | 8 ++++++++
> >> 1 file changed, 8 insertions(+)
> >>
> >>diff --git a/arch/arm/boot/dts/sun8i-a23-gt90h-v4.dts b/arch/arm/boot/dts/sun8i-a23-gt90h-v4.dts
> >>index f27ebbb..da55b5a 100644
> >>--- a/arch/arm/boot/dts/sun8i-a23-gt90h-v4.dts
> >>+++ b/arch/arm/boot/dts/sun8i-a23-gt90h-v4.dts
> >>@@ -53,6 +53,14 @@
> >> 	status = "okay";
> >> };
> >>
> >>+&gsl1680 {
> >>+	compatible = "silead,gsl3675";
> >>+	touchscreen-fw-name = "silead/gsl3675-gt90h.fw";
> >
> >That's not documented anywhere, and looks really suspicious.
> 
> Ugh, that should have been in:
> 
> Documentation/devicetree/bindings/input/touchscreen/silead_gsl1680.txt
> 
> But somehow it is not (I believe it was there in earlier revisions of
> the patch), I'll send a patch to fix this.
> 
> About it being suspicious, this is not really firmware it is a bunch
> of configuration data / lookup tables for the controller which tell
> it in which order the touchscreen horizontal / vertical sensor
> lines are connected to its sense pins, and what values to send
> for finger x% between line z and line z+1, which differs per
> tablet model, since not all tablets use the same digitizer.

It's not really the firmware itself that I find suspicious, but more
the encoding of a path to a file in the DT, especially when you can
apparently derive it from other informations already found in the DT
(<vendor>/<compatible>-<board>.fw)

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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