* [PATCH] input: s6sy761: fix coordinate read bit shift
@ 2021-03-05 2:03 Caleb Connolly
2021-03-05 11:55 ` Andi Shyti
0 siblings, 1 reply; 3+ messages in thread
From: Caleb Connolly @ 2021-03-05 2:03 UTC (permalink / raw)
To: caleb, andi, Dmitry Torokhov
Cc: ~postmarketos/upstreaming, phone-devel, linux-input, linux-kernel
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
The touch coordinates are read by shifting a value left by 3,
this is incorrect and effectively causes the coordinates to
be half of the correct value.
Shift by 4 bits instead to report the correct value.
This matches downstream examples, and has been confirmed on my
device (OnePlus 7 Pro).
Signed-off-by: Caleb Connolly <caleb@connolly.tech>
---
drivers/input/touchscreen/s6sy761.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/input/touchscreen/s6sy761.c b/drivers/input/touchscreen/s6sy761.c
index b63d7fdf0cd2..85a1f465c097 100644
--- a/drivers/input/touchscreen/s6sy761.c
+++ b/drivers/input/touchscreen/s6sy761.c
@@ -145,8 +145,8 @@ static void s6sy761_report_coordinates(struct s6sy761_data *sdata,
u8 major = event[4];
u8 minor = event[5];
u8 z = event[6] & S6SY761_MASK_Z;
- u16 x = (event[1] << 3) | ((event[3] & S6SY761_MASK_X) >> 4);
- u16 y = (event[2] << 3) | (event[3] & S6SY761_MASK_Y);
+ u16 x = (event[1] << 4) | ((event[3] & S6SY761_MASK_X) >> 4);
+ u16 y = (event[2] << 4) | (event[3] & S6SY761_MASK_Y);
input_mt_slot(sdata->input, tid);
--
2.29.2
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] input: s6sy761: fix coordinate read bit shift
2021-03-05 2:03 [PATCH] input: s6sy761: fix coordinate read bit shift Caleb Connolly
@ 2021-03-05 11:55 ` Andi Shyti
2021-03-05 17:54 ` Caleb Connolly
0 siblings, 1 reply; 3+ messages in thread
From: Andi Shyti @ 2021-03-05 11:55 UTC (permalink / raw)
To: Caleb Connolly
Cc: Andi Shyti, Dmitry Torokhov, ~postmarketos/upstreaming,
phone-devel, linux-input, linux-kernel
Hi Caleb,
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
Please clean up the commit message.
> The touch coordinates are read by shifting a value left by 3,
> this is incorrect and effectively causes the coordinates to
> be half of the correct value.
>
> Shift by 4 bits instead to report the correct value.
>
> This matches downstream examples, and has been confirmed on my
> device (OnePlus 7 Pro).
The real reason is that from the register we get:
byte 3 byte 2 byte 1
+--------+--------+ +-----------------+ +-----------------+
| | | | | | |
| X[3:0] | Y[3:0] | | Y[11:4] | | X[11:4] |
| | | | | | |
+--------+--------+ +-----------------+ +-----------------+
and the 12 bit values have to fit in a 16bit variable.
The upper 8 bits (in event[2] and event[1] need to be shifted
left by '4' and not by '3' in order to leave space to the lower
4 bits (in event[3]).
>
> Signed-off-by: Caleb Connolly <caleb@connolly.tech>
> ---
> drivers/input/touchscreen/s6sy761.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/input/touchscreen/s6sy761.c b/drivers/input/touchscreen/s6sy761.c
> index b63d7fdf0cd2..85a1f465c097 100644
> --- a/drivers/input/touchscreen/s6sy761.c
> +++ b/drivers/input/touchscreen/s6sy761.c
> @@ -145,8 +145,8 @@ static void s6sy761_report_coordinates(struct s6sy761_data *sdata,
> u8 major = event[4];
> u8 minor = event[5];
> u8 z = event[6] & S6SY761_MASK_Z;
> - u16 x = (event[1] << 3) | ((event[3] & S6SY761_MASK_X) >> 4);
> - u16 y = (event[2] << 3) | (event[3] & S6SY761_MASK_Y);
> + u16 x = (event[1] << 4) | ((event[3] & S6SY761_MASK_X) >> 4);
> + u16 y = (event[2] << 4) | (event[3] & S6SY761_MASK_Y);
the devil knows how that '3' has ended up there :)
Thanks for catching it!
Reviewed-by: Andi Shyti <andi@etezian.org>
Andi
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] input: s6sy761: fix coordinate read bit shift
2021-03-05 11:55 ` Andi Shyti
@ 2021-03-05 17:54 ` Caleb Connolly
0 siblings, 0 replies; 3+ messages in thread
From: Caleb Connolly @ 2021-03-05 17:54 UTC (permalink / raw)
To: Andi Shyti
Cc: Dmitry Torokhov, ~postmarketos/upstreaming, phone-devel,
linux-input, linux-kernel
Hi Andi,
On 05/03/2021 11:55 am, Andi Shyti wrote:
> Hi Caleb,
>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA256
> Please clean up the commit message.
oops! Sorry
>
>> The touch coordinates are read by shifting a value left by 3,
>> this is incorrect and effectively causes the coordinates to
>> be half of the correct value.
>>
>> Shift by 4 bits instead to report the correct value.
>>
>> This matches downstream examples, and has been confirmed on my
>> device (OnePlus 7 Pro).
> The real reason is that from the register we get:
>
> byte 3 byte 2 byte 1
> +--------+--------+ +-----------------+ +-----------------+
> | | | | | | |
> | X[3:0] | Y[3:0] | | Y[11:4] | | X[11:4] |
> | | | | | | |
> +--------+--------+ +-----------------+ +-----------------+
>
> and the 12 bit values have to fit in a 16bit variable.
>
> The upper 8 bits (in event[2] and event[1] need to be shifted
> left by '4' and not by '3' in order to leave space to the lower
> 4 bits (in event[3]).
Thanks for clarifying, sorry for my rather naive commit message.
>> Signed-off-by: Caleb Connolly <caleb@connolly.tech>
>> ---
>> drivers/input/touchscreen/s6sy761.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/input/touchscreen/s6sy761.c b/drivers/input/touchscreen/s6sy761.c
>> index b63d7fdf0cd2..85a1f465c097 100644
>> --- a/drivers/input/touchscreen/s6sy761.c
>> +++ b/drivers/input/touchscreen/s6sy761.c
>> @@ -145,8 +145,8 @@ static void s6sy761_report_coordinates(struct s6sy761_data *sdata,
>> u8 major = event[4];
>> u8 minor = event[5];
>> u8 z = event[6] & S6SY761_MASK_Z;
>> - u16 x = (event[1] << 3) | ((event[3] & S6SY761_MASK_X) >> 4);
>> - u16 y = (event[2] << 3) | (event[3] & S6SY761_MASK_Y);
>> + u16 x = (event[1] << 4) | ((event[3] & S6SY761_MASK_X) >> 4);
>> + u16 y = (event[2] << 4) | (event[3] & S6SY761_MASK_Y);
> the devil knows how that '3' has ended up there :)
>
> Thanks for catching it!
>
> Reviewed-by: Andi Shyti <andi@etezian.org>
Regards,
Caleb
>
> Andi
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-03-05 2:03 [PATCH] input: s6sy761: fix coordinate read bit shift Caleb Connolly
2021-03-05 11:55 ` Andi Shyti
2021-03-05 17:54 ` Caleb Connolly
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