linux-kernel - Re: [PATCH] input: goodix: Check the 'data ready' bit before reading data

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Message-ID: <df24297181d7b061f4c31f7fe118bdf6@mail.crapouillou.net>
Date:	Mon, 27 Apr 2015 11:00:26 +0200
From:	paul <paul@...pouillou.net>
To:	Bastien Nocera <hadess@...ess.net>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] input: goodix: Check the 'data ready' bit before
 reading data

Hi Bastien,

Ok, I will send a V2 with a better commit message then.

-Paul

Le 2015-04-25 14:54, Bastien Nocera a écrit :
> On Sat, 2015-04-25 at 12:48 +0200, Paul Cercueil wrote:
>> The MSB of the first byte read via I2C seems to indicate whether the
>> data is valid (or ready) when an interrupt is raised. Previously,
>> this
>> bit was ignored, which resulted in a lot of incorrect detections of
>> "finger removed" events.
> 
> This seems correct, but the wording doesn't match the language used in
> the Goodix docs that were posted here some time ago[1].
> 
> I would have written:
> The MSB of the first byte read via I2C at the coordinates address
> indicate whether the data is valid or ready (called "buffer status" in
> the datasheets) when an interrupt is raised. Previously, this bit was
> ignored, which resulted in a lot of incorrect detections of "finger
> removed" events.
> 
> And for the commit subject:
> input: goodix: Check the 'buffer status' bit before reading data
> 
> This seems correct otherwise.
> 
> Signed-off-by: Bastien Nocera <hadess@...ess.net>
> 
> with the fixed commit message/subject
> 
> [1]: Linked from the device tree support patch:
> https://patchwork.ozlabs.org/patch/446838/
> Page 16, table c, 0x814E is what we read for coordinates
> 
>> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>> ---
>>  drivers/input/touchscreen/goodix.c | 3 +++
>>  1 file changed, 3 insertions(+)
>> 
>> diff --git a/drivers/input/touchscreen/goodix.c
>> b/drivers/input/touchscreen/goodix.c
>> index ca19668..9fa6c5f 100644
>> --- a/drivers/input/touchscreen/goodix.c
>> +++ b/drivers/input/touchscreen/goodix.c
>> @@ -98,6 +98,9 @@ static int goodix_ts_read_input_report(struct
>> goodix_ts_data *ts, u8 *data)
>>               return error;
>>       }
>> 
>> +     if (!(data[0] & 0x80))
>> +             return -EAGAIN;
>> +
>>       touch_num = data[0] & 0x0f;
>>       if (touch_num > GOODIX_MAX_CONTACTS)
>>               return -EPROTO;
--
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