linux-kernel - Re: [PATCH v2 2/9] input: elants: support old touch report format

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Date:   Fri, 13 Dec 2019 03:06:09 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     linux-input@...r.kernel.org, devicetree@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-kernel@...r.kernel.org, Henrik Rydberg <rydberg@...math.org>,
        James Chen <james.chen@....com.tw>,
        Johnny Chuang <johnny.chuang@....com.tw>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh-dt@...nel.org>,
        Scott Liu <scott.liu@....com.tw>
Subject: Re: [PATCH v2 2/9] input: elants: support old touch report format

12.12.2019 22:45, Michał Mirosław пишет:
> 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);

Okay, I also don't know how to test it properly.

If anyone knows, please let us know :)