Re: [RESEND PATCH 1/2] Input: mt6779-keypad - fix hardware code mapping

From: Mattijs Korpershoek <mkorpershoek@baylibre.com>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno 
	<angelogioacchino.delregno@collabora.com>,
	Kevin Hilman <khilman@baylibre.com>,
	Fabien Parent <fparent@baylibre.com>,
	linux-input@vger.kernel.org, linux-mediatek@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RESEND PATCH 1/2] Input: mt6779-keypad - fix hardware code mapping
Date: Mon, 16 May 2022 09:30:52 +0200	[thread overview]
Message-ID: <874k1qkk7n.fsf@baylibre.com> (raw)
In-Reply-To: <YoHf6Z4HTfh4Y+bn@google.com>

Hi Dmitry,

Thank you for your review,

On dim., mai 15, 2022 at 22:23, Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote:

> On Fri, May 13, 2022 at 05:18:44PM +0200, Mattijs Korpershoek wrote:
>> In mt6779_keypad_irq_handler(), we
>> 1. Read a hardware code from KPD_MEM1 -> KPD_MEM5
>> 2. Use that hardware code to compute columns/rows for the standard
>>    keyboard matrix.
>> 
>> According to the (non-public) datasheet, the
>> map between the hardware code and the cols/rows is:
>> 
>>         |(0)  |(1)  |(2)
>>     ----*-----*-----*-----
>>         |     |     |
>>         |(9)  |(10) |(11)
>>     ----*-----*-----*-----
>>         |     |     |
>>         |(18) |(19) |(20)
>>     ----*-----*-----*-----
>>         |     |     |
>> 
>> This brings us to another formula:
>> -> row = code / 9;
>> -> col = code % 3;
>
> What if there are more than 3 columns?
That's not supported, in hardware, according to the datasheet.

The datasheet I have states that "The interface of MT6763 only supports
3*3 single or 2*2 double, but internal ASIC still detects keys in the
manner of 8*8 single, and 3*3 double. The registers and key codes still
follows the legacy naming".

Should I add another patch in this series to add that limitation in the
probe? There are no checks done in the probe() right now.

>
>> 
>> Implement this mapping in bitnr_to_col_row() to fetch the
>> correct input event from keypad->input_dev->keycode and report that
>> back to userspace.
>> 
>> Fixes: f28af984e771 ("Input: mt6779-keypad - add MediaTek keypad driver")
>> Co-developed-by: Fabien Parent <fparent@baylibre.com>
>> Signed-off-by: Fabien Parent <fparent@baylibre.com>
>> Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
>> ---
>>  drivers/input/keyboard/mt6779-keypad.c | 16 ++++++++++++++--
>>  1 file changed, 14 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/input/keyboard/mt6779-keypad.c b/drivers/input/keyboard/mt6779-keypad.c
>> index 2e7c9187c10f..23360de20da5 100644
>> --- a/drivers/input/keyboard/mt6779-keypad.c
>> +++ b/drivers/input/keyboard/mt6779-keypad.c
>> @@ -36,6 +36,19 @@ static const struct regmap_config mt6779_keypad_regmap_cfg = {
>>  	.max_register = 36,
>>  };
>>  
>> +/*
>> + * | hardware key code | col0 | col1 | col2|
>> + * | ----------------- | -----| ---- | --- |
>> + * | row0              | 0    | 1    | 2   |
>> + * | row1              | 9    | 10   | 11  |
>> + * | row2              | 18   | 19   | 20  |
>> + */
>> +static void bitnr_to_col_row(int bit_nr, int *col, int *row)
>> +{
>> +	*row = bit_nr / 9;
>> +	*col = bit_nr % 3;
>> +}
>> +
>>  static irqreturn_t mt6779_keypad_irq_handler(int irq, void *dev_id)
>>  {
>>  	struct mt6779_keypad *keypad = dev_id;
>> @@ -61,8 +74,7 @@ static irqreturn_t mt6779_keypad_irq_handler(int irq, void *dev_id)
>>  		if (bit_nr % 32 >= 16)
>>  			continue;
>>  
>> -		row = bit_nr / 32;
>> -		col = bit_nr % 32;
>> +		bitnr_to_col_row(bit_nr, &col, &row);
>>  		scancode = MATRIX_SCAN_CODE(row, col, row_shift);
>>  		/* 1: not pressed, 0: pressed */
>>  		pressed = !test_bit(bit_nr, new_state);
>> -- 
>> 2.32.0
>> 
>
> -- 
> Dmitry