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SubjectRe: [PATCH v2 2/9] input: elants: support old touch report format
On Thu, Dec 12, 2019 at 03:54:13AM +0300, Dmitry Osipenko wrote:
> 11.12.2019 19:03, Michał Mirosław пишет:
> > Support ELAN touchpad sensor with older firmware as found on eg. Asus
> > Transformer Pads.
[...]
> > @@ -814,8 +817,16 @@ static void elants_i2c_mt_event(struct elants_data *ts, u8 *buf)
> > pos = &buf[FW_POS_XY + i * 3];
> > x = (((u16)pos[0] & 0xf0) << 4) | pos[1];
> > y = (((u16)pos[0] & 0x0f) << 8) | pos[2];
> > - p = buf[FW_POS_PRESSURE + i];
> > - w = buf[FW_POS_WIDTH + i];
> > + if (report_len == PACKET_SIZE_OLD) {
> > + w = buf[FW_POS_WIDTH + i / 2];
> > + w >>= 4 * (~i & 1); // little-endian-nibbles
> > + w |= w << 4;
> > + w |= !w;
> > + p = w;
>
> Did you copy this from the downstream driver as-is? I'm looking at the
> Nexus 7 driver and it does the following for older format:
>
> u8 size_idx[] = { 35, 35, 36, 36, 37, 37, 38, 38, 39, 39 };
> unsigned int s;
>
> if (i & 1)
> s = buf[size_idx[i]];
> else
> s = buf[size_idx[i]] / 16;
>
> w = s & 0xf;
> p = s * 16;

This is the same thing modulo (w), which is scaled here to declared axis
range (1-255 from 0-15, assuming 0 means "no touch" so it should not occur).

OTOH, I admit, that I don't have any software that can verify those
settings. It might be that eg. one of MT_PRESSURE or MT_TOUCH_MAJOR axes
should be dropped in this case, but with no docs I can't be sure what
the reported values really are.

This is from the original (GPL) code dump labeled 'Asus 10_6_1_27_5':

| touch_size = ((i & 0x01) ? buf[size_index[i]] : (buf[size_index[i]] >> 4)) & 0x0F;
| if(touch_size == 0) touch_size = 1;
| if (touch_size <= 7)
| touch_size = touch_size << 5;
| else
| touch_size = 255;
|
| input_report_abs(idev, ABS_MT_TOUCH_MAJOR, touch_size);
| input_report_abs(idev, ABS_MT_PRESSURE, touch_size);


Best Regards,
Michał Mirosław

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