linux-kernel - Re: [PATCH v7 09/11] input: keyboard: Add support for MAX7360 keypad

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Message-Id: <D9LPB49CQJDW.3VMFI0TFGV7K2@bootlin.com>
Date: Fri, 02 May 2025 15:15:34 +0200
From: "Mathieu Dubois-Briand" <mathieu.dubois-briand@...tlin.com>
To: "Andy Shevchenko" <andriy.shevchenko@...el.com>
Cc: "Lee Jones" <lee@...nel.org>, "Rob Herring" <robh@...nel.org>,
 "Krzysztof Kozlowski" <krzk+dt@...nel.org>, "Conor Dooley"
 <conor+dt@...nel.org>, "Kamel Bouhara" <kamel.bouhara@...tlin.com>, "Linus
 Walleij" <linus.walleij@...aro.org>, "Bartosz Golaszewski" <brgl@...ev.pl>,
 "Dmitry Torokhov" <dmitry.torokhov@...il.com>,
 Uwe Kleine-König <ukleinek@...nel.org>, "Michael Walle"
 <mwalle@...nel.org>, "Mark Brown" <broonie@...nel.org>, "Greg
 Kroah-Hartman" <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, "Danilo Krummrich" <dakr@...nel.org>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
 <linux-gpio@...r.kernel.org>, <linux-input@...r.kernel.org>,
 <linux-pwm@...r.kernel.org>, Grégory Clement
 <gregory.clement@...tlin.com>, "Thomas Petazzoni"
 <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v7 09/11] input: keyboard: Add support for MAX7360
 keypad

On Fri May 2, 2025 at 12:46 PM CEST, Andy Shevchenko wrote:
> On Mon, Apr 28, 2025 at 01:57:27PM +0200, Mathieu Dubois-Briand wrote:
>> Add driver for Maxim Integrated MAX7360 keypad controller, providing
>> support for up to 64 keys, with a matrix of 8 columns and 8 rows.
>
> ...
>
>> +static irqreturn_t max7360_keypad_irq(int irq, void *data)
>> +{
>> +	struct max7360_keypad *max7360_keypad = data;
>> +	struct device *dev = max7360_keypad->input->dev.parent;
>> +	unsigned int val;
>> +	unsigned int row, col;
>> +	unsigned int release;
>> +	unsigned int code;
>> +	int error;
>> +
>> +	do {
>> +		error = regmap_read(max7360_keypad->regmap, MAX7360_REG_KEYFIFO, &val);
>> +		if (error) {
>> +			dev_err(dev, "Failed to read max7360 FIFO");
>> +			return IRQ_NONE;
>> +		}
>> +
>> +		/* FIFO overflow: ignore it and get next event. */
>> +		if (val == MAX7360_FIFO_OVERFLOW)
>> +			dev_warn(dev, "max7360 FIFO overflow");
>
> If many events are missing this will flood the logs, perhaps _ratelimited() ?
>
>> +	} while (val == MAX7360_FIFO_OVERFLOW);
>
> regmap_read_poll_timeout() ?
>

OK, I can try something like:

+       error = regmap_read(max7360_keypad->regmap, MAX7360_REG_KEYFIFO, &val);
+
+       /* FIFO overflow: ignore it and get next event. */
+       if (!error && (val == MAX7360_FIFO_OVERFLOW)) {
+               dev_warn(dev, "max7360 FIFO overflow");
+               error = regmap_read_poll_timeout(max7360_keypad->regmap, MAX7360_REG_KEYFIFO,
+                                                val, val != MAX7360_FIFO_OVERFLOW, 0, 0);
+       }
+
+       if (error) {
+               dev_err(dev, "Failed to read max7360 FIFO");
+               return IRQ_NONE;
+       }
+

Sleep_us is 0 as we are in the IRQ handler, but I'm not sure about
timeout_us. We could set one to make sure we are not stuck in the IRQ
handler, but the IRQ would fire again right after we return. I will stay
with 0 for now.

Also, the "max7360 FIFO overflow" message would be shown at most once
per IRQ, so probably no need for dev_warn_ratelimited().

>> +	if (val == MAX7360_FIFO_EMPTY) {
>> +		dev_dbg(dev, "Got a spurious interrupt");
>> +
>> +		return IRQ_NONE;
>> +	}
>> +
>> +	row = FIELD_GET(MAX7360_FIFO_ROW, val);
>> +	col = FIELD_GET(MAX7360_FIFO_COL, val);
>> +	release = val & MAX7360_FIFO_RELEASE;
>> +
>> +	code = MATRIX_SCAN_CODE(row, col, MAX7360_ROW_SHIFT);
>> +
>> +	dev_dbg(dev, "key[%d:%d] %s\n", row, col, release ? "release" : "press");
>> +
>> +	input_event(max7360_keypad->input, EV_MSC, MSC_SCAN, code);
>> +	input_report_key(max7360_keypad->input, max7360_keypad->keycodes[code], !release);
>> +	input_sync(max7360_keypad->input);
>> +
>> +	return IRQ_HANDLED;
>> +}
>
> ...
>

OK with other comments.

Thanks for your review.
Mathieu

-- 
Mathieu Dubois-Briand, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com