linux-kernel - [RFC/RFT PATCH] pinctrl: bcm2835: don't -EINVAL on alternate funcs from get

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Message-ID: <20250219102750.38519-1-brgl@bgdev.pl>
Date: Wed, 19 Feb 2025 11:27:50 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Ray Jui <rjui@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Stefan Wahren <wahrenst@....net>,
	Liao Chen <liaochen4@...wei.com>,
	Chen-Yu Tsai <wens@...e.org>,
	Mark Brown <broonie@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>
Cc: linux-gpio@...r.kernel.org,
	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [RFC/RFT PATCH] pinctrl: bcm2835: don't -EINVAL on alternate funcs from get_direction()

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

Since commit 9d846b1aebbe ("gpiolib: check the return value of
gpio_chip::get_direction()") we check the return value of the
get_direction() callback as per its API contract. This driver returns
-EINVAL if the pin in question is set to one of the alternative
(non-GPIO) functions. This isn't really an error that should be
communicated to GPIOLIB so default to returning the "safe" value of
INPUT in this case. The GPIO subsystem does not have the notion of
"unknown" direction.

Fixes: 9d846b1aebbe ("gpiolib: check the return value of gpio_chip::get_direction()")
Reported-by: Mark Brown <broonie@...nel.org>
Closes: https://lore.kernel.org/all/Z7VFB1nST6lbmBIo@finisterre.sirena.org.uk/
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 drivers/pinctrl/bcm/pinctrl-bcm2835.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/pinctrl/bcm/pinctrl-bcm2835.c b/drivers/pinctrl/bcm/pinctrl-bcm2835.c
index cc1fe0555e19..eaeec096bc9a 100644
--- a/drivers/pinctrl/bcm/pinctrl-bcm2835.c
+++ b/drivers/pinctrl/bcm/pinctrl-bcm2835.c
@@ -346,14 +346,14 @@ static int bcm2835_gpio_get_direction(struct gpio_chip *chip, unsigned int offse
 	struct bcm2835_pinctrl *pc = gpiochip_get_data(chip);
 	enum bcm2835_fsel fsel = bcm2835_pinctrl_fsel_get(pc, offset);
 
-	/* Alternative function doesn't clearly provide a direction */
-	if (fsel > BCM2835_FSEL_GPIO_OUT)
-		return -EINVAL;
+	if (fsel == BCM2835_FSEL_GPIO_OUT)
+		return GPIO_LINE_DIRECTION_OUT;
 
-	if (fsel == BCM2835_FSEL_GPIO_IN)
-		return GPIO_LINE_DIRECTION_IN;
-
-	return GPIO_LINE_DIRECTION_OUT;
+	/*
+	 * Alternative function doesn't clearly provide a direction. Default
+	 * to INPUT.
+	 */
+	return GPIO_LINE_DIRECTION_IN;
 }
 
 static void bcm2835_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
-- 
2.45.2