[PATCH v3] gpiolib: fix hogs with multiple lines

[Bartosz Golaszewski]

After moving GPIO hog handling into GPIOLIB core, we accidentally stopped
supporting devicetree hog definitions with multiple lines like so:

	hog {
		gpio-hog;
		gpios = <3 0>, <4 GPIO_ACTIVE_LOW>;
		output-high;
		line-name = "foo";
	};

Restore this functionality to fix reported regressions.

Fixes: d1d564ec4992 ("gpio: move hogs into GPIO core")
Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/CAMuHMdX6RuZXAozrF5m625ZepJTVVr4pcyKczSk12MedWvoejw@xxxxxxxxxxxxxx/
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
---
Changes in v3:
- Fix types for some variables
- Make the return value check for "#gpio-cells" property stricter
- Link to v2: https://patch.msgid.link/20260326-gpio-hogs-multiple-v2-1-7c3813460e4f@xxxxxxxxxxxxxxxx

Changes in v2:
- Use a default value of 2 for the number of GPIO cells
- Use kzalloc_objs() instead of kcalloc()
- Propagate the error number from fwnode_property_read_u32()
- Remove special cases forced by the lack of default cells value
- Link to v1: https://patch.msgid.link/20260325-gpio-hogs-multiple-v1-1-7e3a7347f0d6@xxxxxxxxxxxxxxxx
---
 drivers/gpio/gpiolib.c | 92 +++++++++++++++++++++++++++++---------------------
 1 file changed, 54 insertions(+), 38 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 7ee45ccdf1265e94b68fe8fa0d10dbc6adccd93a..96c776ff2669ed2404048360297cf706bfe38251 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -938,12 +938,18 @@ int gpiochip_add_hog(struct gpio_chip *gc, struct fwnode_handle *fwnode)
 	struct fwnode_handle *gc_node = dev_fwnode(&gc->gpiodev->dev);
 	struct fwnode_reference_args gpiospec;
 	enum gpiod_flags dflags;
+	const char *name = NULL;
 	struct gpio_desc *desc;
+	unsigned int num_hogs;
 	unsigned long lflags;
-	const char *name;
 	int ret, argc;
-	u32 gpios[3]; /* We support up to three-cell bindings. */
-	u32 cells;
+	/*
+	 * For devicetree-based systems, this needs to be defined in bindings
+	 * and there's no real default value. For other firmware descriptions
+	 * it makes the most sense to use 2 cells for the GPIO offset and
+	 * request flags.
+	 */
+	u32 cells = 2;
 
 	lflags = GPIO_LOOKUP_FLAGS_DEFAULT;
 	dflags = GPIOD_ASIS;
@@ -952,42 +958,22 @@ int gpiochip_add_hog(struct gpio_chip *gc, struct fwnode_handle *fwnode)
 	argc = fwnode_property_count_u32(fwnode, "gpios");
 	if (argc < 0)
 		return argc;
-	if (argc > 3)
-		return -EINVAL;
 
-	ret = fwnode_property_read_u32_array(fwnode, "gpios", gpios, argc);
-	if (ret < 0)
+	ret = fwnode_property_read_u32(gc_node, "#gpio-cells", &cells);
+	if (ret && is_of_node(fwnode))
 		return ret;
+	if (argc % cells)
+		return -EINVAL;
 
-	if (is_of_node(fwnode)) {
-		/*
-		 * OF-nodes need some additional special handling for
-		 * translating of devicetree flags.
-		 */
-		ret = fwnode_property_read_u32(gc_node, "#gpio-cells", &cells);
-		if (ret)
-			return ret;
-		if (!ret && argc != cells)
-			return -EINVAL;
-
-		memset(&gpiospec, 0, sizeof(gpiospec));
-		gpiospec.fwnode = fwnode;
-		gpiospec.nargs = argc;
+	num_hogs = argc / cells;
 
-		for (int i = 0; i < argc; i++)
-			gpiospec.args[i] = gpios[i];
+	u32 *gpios __free(kfree) = kzalloc_objs(*gpios, argc);
+	if (!gpios)
+		return -ENOMEM;
 
-		ret = of_gpiochip_get_lflags(gc, &gpiospec, &lflags);
-		if (ret)
-			return ret;
-	} else {
-		/*
-		 * GPIO_ACTIVE_LOW is currently the only lookup flag
-		 * supported for non-OF firmware nodes.
-		 */
-		if (gpios[1])
-			lflags |= GPIO_ACTIVE_LOW;
-	}
+	ret = fwnode_property_read_u32_array(fwnode, "gpios", gpios, argc);
+	if (ret < 0)
+		return ret;
 
 	if (fwnode_property_present(fwnode, "input"))
 		dflags |= GPIOD_IN;
@@ -1000,11 +986,41 @@ int gpiochip_add_hog(struct gpio_chip *gc, struct fwnode_handle *fwnode)
 
 	fwnode_property_read_string(fwnode, "line-name", &name);
 
-	desc = gpiochip_get_desc(gc, gpios[0]);
-	if (IS_ERR(desc))
-		return PTR_ERR(desc);
+	for (unsigned int i = 0; i < num_hogs; i++) {
+		if (is_of_node(fwnode)) {
+			/*
+			 * OF-nodes need some additional special handling for
+			 * translating of devicetree flags.
+			 */
+			memset(&gpiospec, 0, sizeof(gpiospec));
+			gpiospec.fwnode = fwnode;
+			gpiospec.nargs = cells;
+
+			for (unsigned int j = 0; j < cells; j++)
+				gpiospec.args[j] = gpios[i * cells + j];
+
+			ret = of_gpiochip_get_lflags(gc, &gpiospec, &lflags);
+			if (ret)
+				return ret;
+		} else {
+			/*
+			 * GPIO_ACTIVE_LOW is currently the only lookup flag
+			 * supported for non-OF firmware nodes.
+			 */
+			if (gpios[i * cells + 1])
+				lflags |= GPIO_ACTIVE_LOW;
+		}
+
+		desc = gpiochip_get_desc(gc, gpios[i * cells]);
+		if (IS_ERR(desc))
+			return PTR_ERR(desc);
 
-	return gpiod_hog(desc, name, lflags, dflags);
+		ret = gpiod_hog(desc, name, lflags, dflags);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
 }
 
 static int gpiochip_hog_lines(struct gpio_chip *gc)

---
base-commit: b99f90909bdc937914fd6017d67b66d445273650
change-id: 20260325-gpio-hogs-multiple-1718d38c1f5b

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>