linux-kernel - Re: [PATCH 14/22 v4] Input: atmel_mxt_ts - don't re-read matrix after applying pdata

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Message-ID: <4FE053BD.2090605@itdev.co.uk>
Date:	Tue, 19 Jun 2012 11:26:05 +0100
From:	Nick Dyer <nick.dyer@...ev.co.uk>
To:	Yufeng Shen <miletus@...gle.com>
CC:	Daniel Kurtz <djkurtz@...omium.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	linux-input@...r.kernel.org,
	Iiro Valkonen <iiro.valkonen@...el.com>,
	Benson Leung <bleung@...omium.org>,
	Olof Johansson <olofj@...omium.org>,
	linux-kernel@...r.kernel.org,
	"Bowens, Alan" <Alan.Bowens@...el.com>
Subject: Re: [PATCH 14/22 v4] Input: atmel_mxt_ts - don't re-read matrix after
 applying pdata

Yufeng Shen wrote:
> On Mon, Jun 18, 2012 at 11:03 AM, Nick Dyer <nick.dyer@...ev.co.uk> wrote:
>> Daniel Kurtz wrote:
>>> The matrix x/y size in the Info ID Block represents the number of x/y
>>> trace lines on the device.  There is no need to re-read them after
>>> applying pdata config, since pdata only configures the object table
>>> etnries.  The matrix size read from the ID can only be updated by a
>>> firmware update.
>>
>> This isn't correct. For example, mXT224 can be configured as 16x14, 17x13,
>> 18x12, etc. This only takes effect when the chip is reset, which is why it
>> is necessary to re-read them after applying the config.
> 
> so look at structure mxt_info
> 
>  struct mxt_info {
>           u8 family_id;
>           u8 variant_id;
>           u8 version;
>           u8 build;
>           u8 matrix_xsize;
>           u8 matrix_ysize;
>           u8 object_num;
> };
> 
> I think it is meant to be corresponding to Information Block of the
> device, of which
> the matrix_xsize and matrix_ysize mean "The size of the matrix the
> device supports",
> which should be fixed for a certain chip.

As I said, it's not fixed, there is a mode setting (T28 byte 2) which
alters the matrix size. This is documented in the protocol guide, if you
have it.

You can also verify this if you want: change mode setting, backup, reset,
and read the information block, you'll see the matrix size changes. I've
just checked that myself on an mXT224.

I also asked the guys at Atmel that I work with, and they confirm that this
behaviour is as designed.

> The configurable matrix size is in T9 XSIZE/YSIZE, which, if ever
> needed to be read back,
> probably read back into something other than mxt_info struct.

The position of the touchscreen within the matrix is a separate
configurable setting, you're confusing the two.

cheers

-- 
Nick Dyer
Software Engineer, ITDev Ltd
Hardware and Software Development Consultancy
Website: http://www.itdev.co.uk
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