linux-kernel - Re: [PATCH 2/6] Input: elantech - use firmware provided x, y ranges

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Message-ID: <4E4E54BE.5000108@tudelft.nl>
Date:	Fri, 19 Aug 2011 14:19:10 +0200
From:	Éric Piel <E.A.B.Piel@...elft.nl>
To:	JJ Ding <jj_ding@....com.tw>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Seth Forshee <seth.forshee@...onical.com>,
	Aaron Huang <aaron_huang@....com.tw>,
	Tom Lin <tom_lin@....com.tw>,
	Daniel Kurtz <djkurtz@...omium.org>,
	Chase Douglas <chase.douglas@...onical.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	Alessandro Rubini <rubini@...l.unipv.it>
Subject: Re: [PATCH 2/6] Input: elantech - use firmware provided x, y ranges

Op 19-08-11 11:47, JJ Ding schreef:
> Hi Dmitry,
>
> Sorry for late reply. I missed this one somehow.
>
> On Thu, 18 Aug 2011 00:47:56 -0700, Dmitry Torokhov<dmitry.torokhov@...il.com>  wrote:
>> On Thu, Aug 18, 2011 at 09:57:05AM +0800, JJ Ding wrote:
>>> +
>>> +		i = (etd->fw_version>  0x020800&&
>>> +		     etd->fw_version<  0x020900) ? 1 : 2;
>>> +		*x_max = (etd->capabilities[1] - i) * 64;
>>> +		*y_max = (etd->capabilities[2] - i) * 64;
>>> +		*y_2ft_max = (*y_max - i) * 64 / 4;
>>
>> Hmm, we should have the same range for ST and MT data and scale MT data
>> if it has lower resolution to match ST.
> So I should just remove y_2ft_max and those ETP_2FT_XXXX in elantech.h,
> and do the scale in elantech_report_absolute_v2?
Humm, yes, I think what Dmitry wants is that both ABS_MT_POSITION_Y and 
ABS_Y have the same min and max, and the scaling is done when reading 
the data. However, it seems this already what is being tried to be done, 
excepted that I mess it up in the latest patch set I sent. I just 
noticed it now, sorry :-S

You can see in elantech_report_absolute_v2() in case of 2 fingers:
The part for updating ABS_X, ABS_Y is correct:
  input_report_abs(dev, ABS_X, x1 << 2);
  input_report_abs(dev, ABS_Y, y1 << 2);

But I forgot to do the same for MT:
  elantech_report_semi_mt_data(dev, fingers, x1, y1, x2, y2);
That should be:
  elantech_report_semi_mt_data(dev, fingers, x1 << 2, y1 << 2, x2 << 2, 
y2 << 2);

Or, even more clean, just move the shift directly into the computation, 
like:
  y1 = etd->y_max - ((((packet[0] & 0x20) << 3) | packet[2]) << 2);

In such case you can drop completely y_2ft_max, and move the 
input_report_abs() outside of the switch.


In addition, I have a couple of more remarks on this patch:
> +		*x_max = (etd->capabilities[1] - i) * 64;
> +		*y_max = (etd->capabilities[2] - i) * 64;
> +		*y_2ft_max = (*y_max - i) * 64 / 4;
This last line is probably wrong as I think it should be:
  *y_2ft_max = *y_max / 4;

But if you drop y_2ft_max, that shouldn't matter anymore!
> +	case 1:
> +		*x_min = ETP_XMIN_V1;
> +		*y_min = ETP_YMIN_V1;
> +		*x_max = ETP_XMAX_V1;
> +		*y_max = ETP_YMAX_V1;
> +		break;
> +
> +	case 2:
> +		if (etd->fw_version == 0x020800 ||
> +		    etd->fw_version == 0x020b00 ||
> +		    etd->fw_version == 0x020030) {
> +			*x_min = ETP_XMIN_V2;
> +			*y_min = ETP_YMIN_V2;
> +			*x_max = ETP_XMAX_V2;
> +			*y_max = ETP_YMAX_V2;
> +			*y_2ft_max = ETP_2FT_YMAX;
> +			break;
> +		}

Actually these variables are defined as:
#define ETP_YMAX_V2	( 768 - ETP_EDGE_FUZZ_V2)

I'd suggest to remove trying being too clever and remove the 
ETP_EDGE_FUZZ_V2. They should be just the raw resolution of the device. 
Otherwise, they can cause underflow on the Y axis.

Finally, a minor style suggestion, in "case 2:" above, only use one 
single "break;" and put the two part in a complete "if-else" statement, 
with xmin, y_min all explicit. E.g.:
case 2:
	if (etd->fw_version == 0x020800 ||
	    etd->fw_version == 0x020b00 ||
	    etd->fw_version == 0x020030) {
		*x_min = ETP_XMIN_V2;
		*y_min = ETP_YMIN_V2;
		*x_max = ETP_XMAX_V2;
		*y_max = ETP_YMAX_V2;
	} else {
		i = (etd->fw_version > 0x020800 &&
		     etd->fw_version < 0x020900) ? 1 : 2;
		*x_min = 0;
		*y_min = 0;
		*x_max = (etd->capabilities[1] - i) * 64;
		*y_max = (etd->capabilities[2] - i) * 64;
	}
	break;

> If so, I will create another patch for this change.
>
If you could send a new version of this patch with these changes, it'd 
be great :-)

Cheers,
Éric
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