linux-kernel - Re: [PATCH v2 7/7] Input: matrix_keypad

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Message-ID: <ZypvrAYCX8lYUltX@google.com>
Date: Tue, 5 Nov 2024 11:19:08 -0800
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Markus Burri <markus.burri@...com>
Cc: linux-kernel@...r.kernel.org, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Marek Vasut <marek.vasut@...il.com>, linux-input@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 7/7] Input: matrix_keypad - detect change during scan

On Tue, Nov 05, 2024 at 02:03:22PM +0100, Markus Burri wrote:
> For a setup where the matrix keypad is connected over a slow interface
> (e.g. a gpio-expansion over i2c), the scan can take a longer time to read.
> 
> Interrupts need to be disabled during scan. And therefore changes in this
> period are not detected.
> To improve this situation, scan the matrix again if the row state changed
> during interrupts disabled.

And what if the state changes yet again during the 2nd scan attempt?

> 
> Signed-off-by: Markus Burri <markus.burri@...com>
> ---
>  drivers/input/keyboard/matrix_keypad.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/input/keyboard/matrix_keypad.c b/drivers/input/keyboard/matrix_keypad.c
> index 46873b8..93c8404 100644
> --- a/drivers/input/keyboard/matrix_keypad.c
> +++ b/drivers/input/keyboard/matrix_keypad.c
> @@ -126,6 +126,10 @@ static void matrix_keypad_scan(struct work_struct *work)
>  	const unsigned short *keycodes = input_dev->keycode;
>  	uint32_t new_state[MATRIX_MAX_COLS];
>  	int row, col, code;
> +	u32 init_row_state, new_row_state;
> +
> +	/* read initial row state to detect changes between scan */
> +	init_row_state = read_row_state(keypad);
>  
>  	/* de-activate all columns for scanning */
>  	activate_all_cols(keypad, false);
> @@ -174,6 +178,19 @@ static void matrix_keypad_scan(struct work_struct *work)
>  	keypad->scan_pending = false;
>  	enable_row_irqs(keypad);
>  	spin_unlock_irq(&keypad->lock);
> +
> +	/* read new row state and detect if value has changed */
> +	new_row_state = read_row_state(keypad);
> +	if (init_row_state != new_row_state) {
> +		spin_lock_irq(&keypad->lock);
> +		if (likely(!keypad->scan_pending && !keypad->stopped)) {
> +			disable_row_irqs(keypad);
> +			keypad->scan_pending = true;
> +			schedule_delayed_work(&keypad->work,
> +					      msecs_to_jiffies(keypad->debounce_ms));
> +		}
> +		spin_unlock_irq(&keypad->lock);
> +	}
>  }
>  
>  static irqreturn_t matrix_keypad_interrupt(int irq, void *id)
> -- 
> 2.39.5
> 

-- 
Dmitry