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Subject: Re: [PATCH v5 07/10] input: elants: support 0x66 reply opcode for
 reporting touches
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <mirq-linux@rere.qmqm.pl>,
        Johnny Chuang <johnny.chuang@emc.com.tw>
Cc:     David Heidelberg <david@ixit.cz>,
        Henrik Rydberg <rydberg@bitmath.org>,
        James Chen <james.chen@emc.com.tw>,
        Rob Herring <robh+dt@kernel.org>,
        Scott Liu <scott.liu@emc.com.tw>, linux-input@vger.kernel.org,
        linux-kernel@vger.kernel.org
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 <20200518040532.GP89269@dtor-ws>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <268f009f-7bf7-28ce-ff2c-00d033a7bf5f@gmail.com>
Date:   Mon, 18 May 2020 12:10:42 +0300
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18.05.2020 07:05, Dmitry Torokhov пишет:
> On Sun, Apr 26, 2020 at 07:47:52PM +0200, Michał Mirosław wrote:
>> From: Dmitry Osipenko <digetx@gmail.com>
>>
>> eKTF3624 touchscreen firmware uses two variants of the reply opcodes for
>> reporting touch events: one is 0x63 (used by older firmware) and other is
>> 0x66 (used by newer firmware). The 0x66 variant is equal to 0x63 of
>> eKTH3500, while 0x63 needs small adjustment of the touch pressure value.
>>
>> Nexus 7 tablet device has eKTF3624 touchscreen and it uses 0x66 opcode for
>> reporting touch events, let's support it now. Other devices, eg. ASUS TF300T,
>> use 0x63.
>>
>> Note: CMD_HEADER_REK is used for replying to calibration requests, it has
>> the same 0x66 opcode number which eKTF3624 uses for reporting touches.
>> The calibration replies are handled separately from the the rest of the
>> commands in the driver by entering into ELAN_WAIT_RECALIBRATION state
>> and thus this change shouldn't change the old behavior.
> 
> Is it possible to know what format a device will use by querying it at
> probe time?

I guess only somebody from Elan could answer this question. AFAIK,
neither touchscreen firmware sources nor technical documentation aren't
publicly available.

Downstream kernel driver is the only source of information in our case
and it does the same thing as we do in this patch.