linux-kernel - [PATCH v2] gpiolib: allow line names from device props to override driver names

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Date:   Tue, 14 Dec 2021 22:59:56 +0100
From:   Peter Rosin <peda@...ntia.se>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Alexander Dahl <ada@...rsis.com>
Subject: [PATCH v2] gpiolib: allow line names from device props to override
 driver names

Some GPIO providers set names for GPIO lines that match the names of
the pins on the SoC, or variations on that theme. These names are
generic more often that not, such as pioC12 in the at91 case. These
generic names block the possibility to set more useful GPIO line
names with device properties (i.e. gpio-line-names).

Allow overriding a generic name given by the GPIO driver if there is
a name given to the GPIO line using device properties, but leave the
generic name alone if no better name is available.

However, there is a risk. If user space is depending on the above
mentioned fixed GPIO names, AND there are device properties that
previously did not reach the surface, the name change might cause
regressions. But hopefully this stays below the radar...

Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Tested-by: Alexander Dahl <ada@...rsis.com>
Signed-off-by: Peter Rosin <peda@...ntia.se>
---
 drivers/gpio/gpiolib.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

Changes since v1: language fixes and gpio->GPIO as suggested by Andy.
(However, I disagree that "generally generic" is invalid or a tautology,
as it is exactly what I meany to say. But I changed it anyway...)

The tested-by tag is from a backport, zap it if that's not good
enough.

Cheers,
Peter

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index abfbf546d159..817342ef26d0 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -422,8 +422,16 @@ static int devprop_gpiochip_set_names(struct gpio_chip *chip)
 	if (count > chip->ngpio)
 		count = chip->ngpio;

-	for (i = 0; i < count; i++)
-		gdev->descs[i].name = names[chip->offset + i];
+	for (i = 0; i < count; i++) {
+		/*
+		 * Allow overriding "fixed" names provided by the GPIO
+		 * provider. The "fixed" names are more often than not
+		 * generic and less informative than the names given in
+		 * device properties.
+		 */
+		if (names[chip->offset + i] && names[chip->offset + i][0])
+			gdev->descs[i].name = names[chip->offset + i];
+	}

 	kfree(names);

@@ -708,10 +716,12 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	INIT_LIST_HEAD(&gdev->pin_ranges);
 #endif

-	if (gc->names)
+	if (gc->names) {
 		ret = gpiochip_set_desc_names(gc);
-	else
-		ret = devprop_gpiochip_set_names(gc);
+		if (ret)
+			goto err_remove_from_list;
+	}
+	ret = devprop_gpiochip_set_names(gc);
 	if (ret)
 		goto err_remove_from_list;

-- 
2.20.1