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

Hi,

On 08/23/2016 05:17 PM, Maxime Ripard wrote:

On Tue, Aug 23, 2016 at 11:39:06AM +0200, Hans de Goede wrote:

quoted

Hi,

On 23-08-16 11:26, Maxime Ripard wrote:

quoted

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

quoted

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,

It is not a path it is a filename. We could drop the "silead/" prefix
and put that in the driver instead to really make it a filename.

quoted

especially when you can
apparently derive it from other informations already found in the DT
(<vendor>/<compatible>-<board>.fw)

That will not work, sometimes different boards use the same digitizer
and thus the same firmware. Also in case of the q8 tablets, we need
different firmware for different variants (this is to be dealt with
by the q8-hardware-manager I'm working on), since although they
all use the same digitizer they do not wire it up to the controllers
pins the same in all models, so we need different firmware files
corresponding to different wirings.

TL;DR: There is no 1:1 mapping between board and the firmware filename.

The point still holds. It's exactly the same case than the broadcom
nvram filename discussion, and it raised the same issues.

No it is not, in this case we also want to be able to specify
different fw names on devices using the same base dts, here
is a tablet for all the q8 tablets with gsl1680 I've:

a13-94v-0:		a082 a23-tj-a23-q88-v4.0_20140815/GSL1680E_700_FW.fw	1024x600 inverted-x
a13-tzx-713b-v2.1:	a082 a23-tj-a23-q88-v4.0_20140815/GSL1680E_700_FW.fw	1024x600
a23-q8h-v3:		a082 a23-tj-a23-q88-v4.0_20140815/GSL1688_A70_FW.fw	 800x480 swapped-x-y
a23-tj-a23-q88-v4.0:	a082 a23-tj-a23-q88-v4.0_20140815/GSL1680E_700_FW.fw	1024x600
a23-tw-ao721-v41:	a082 a23-tj-a23-q88-v4.0_20140815/GSL1680E_700_FW.fw	1024x600 inverted-x
a23-ippo-q8h-v1.2:	a082 a23-tj-a23-q88-v4.0_20140815/GSL1688_A70_FW.fw	 800x480 swapped-x-y
a33-ippo-q8h-v1.2:	a082 a23-tj-a23-q88-v4.0_20140815/GSL1688_A70_FW.fw	 800x480 swapped-x-y
a33-tzx-723q4:		b482 a33-Q8_V2.4_1118/GSL1680_FW_D702.fw		 960x640 inverted-x
a33-q8-v2.4-1118:	b482 a33-Q8_V2.4_1118/GSL1680_FW_D702.fw		 960x640
a33-q8h-v1.5:		b482 a33-q8h-v1.5/GSL1688_A70_FW.fw			 960x640

I'm working on a q8hardware-mgr (inspired by the beagle bone cape mgr)
to automatically detect the touchscreen controller as well as the controller id
(the 2nd column above), and it will need to set a filename for the firmware
file based on this, deriving this from the machine compatible will
simply not work here.

Regards,

Hans