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

On Mon, Aug 22, 2016 at 09:03:57PM +0200, Hans de Goede wrote:

Hi,

On 22-08-16 20:30, Maxime Ripard wrote:

quoted

On Mon, Aug 08, 2016 at 09:43:14PM +0200, Hans de Goede wrote:

quoted

The gt90h tablet has a gsl3675 touchscreen, add a dt node describing it.

Signed-off-by: Hans de Goede <redacted>
---
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