[PATCH 1/1] gpiolib: allow device numbering using OF alias

[Alexander Stein]

From: Markus Niebel <Markus.Niebel@xxxxxxxxxxxxxxx>

This is useful e.g. for the following cases

- GPIO IP name order is not aligned with SOC addresses
  (i.MX93 from NXP)
- reproducible naming for GPIO expander chips

The implementation is a mix of the one found for MMC and RTC.

Signed-off-by: Markus Niebel <Markus.Niebel@xxxxxxxxxxxxxxx>
Signed-off-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx>
---
imx93 specifies alias for 4 on-chip GPIO controllers. But they are
ignored:
$ ls -o -g /sys/bus/gpio/devices/
total 0
lrwxrwxrwx 1 0 Feb 15 10:03 gpiochip0 -> ../../../devices/platform/soc@0/42000000.bus/42530000.i2c/i2c-2/2-0071/gpiochip0
lrwxrwxrwx 1 0 Feb 15 10:03 gpiochip1 -> ../../../devices/platform/soc@0/42000000.bus/42530000.i2c/i2c-2/2-0072/gpiochip1
lrwxrwxrwx 1 0 Feb 15 10:03 gpiochip2 -> ../../../devices/platform/soc@0/43810080.gpio/gpiochip2
lrwxrwxrwx 1 0 Feb 15 10:03 gpiochip3 -> ../../../devices/platform/soc@0/43820080.gpio/gpiochip3
lrwxrwxrwx 1 0 Feb 15 10:03 gpiochip4 -> ../../../devices/platform/soc@0/43830080.gpio/gpiochip4
lrwxrwxrwx 1 0 Feb 15 10:03 gpiochip5 -> ../../../devices/platform/soc@0/47400080.gpio/gpiochip5
lrwxrwxrwx 1 0 Feb 15 10:03 gpiochip6 -> ../../../devices/platform/soc@0/42000000.bus/42530000.i2c/i2c-2/2-0070/gpiochip6

With this patch this becomes:
$ ls -o -g /sys/bus/gpio/devices/
total 0
lrwxrwxrwx 1 0 Feb 15 10:18 gpiochip0 -> ../../../devices/platform/soc@0/47400080.gpio/gpiochip0
lrwxrwxrwx 1 0 Feb 15 10:18 gpiochip1 -> ../../../devices/platform/soc@0/43810080.gpio/gpiochip1
lrwxrwxrwx 1 0 Feb 15 10:18 gpiochip2 -> ../../../devices/platform/soc@0/43820080.gpio/gpiochip2
lrwxrwxrwx 1 0 Feb 15 10:18 gpiochip3 -> ../../../devices/platform/soc@0/43830080.gpio/gpiochip3
lrwxrwxrwx 1 0 Feb 15 10:18 gpiochip4 -> ../../../devices/platform/soc@0/42000000.bus/42530000.i2c/i2c-2/2-0071/gpiochip4
lrwxrwxrwx 1 0 Feb 15 10:18 gpiochip5 -> ../../../devices/platform/soc@0/42000000.bus/42530000.i2c/i2c-2/2-0072/gpiochip5
lrwxrwxrwx 1 0 Feb 15 10:18 gpiochip6 -> ../../../devices/platform/soc@0/42000000.bus/42530000.i2c/i2c-2/2-0070/gpiochip6

 drivers/gpio/gpiolib.c | 33 +++++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 19bd23044b01..4d606ad522ac 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -663,10 +663,25 @@ static void gpiochip_setup_devs(void)
 	}
 }
 
+/**
+ * gpio_first_nonreserved_index() - get the first index that is not reserved
+ */
+static int gpio_first_nonreserved_index(void)
+{
+	int max;
+
+	max = of_alias_get_highest_id("gpio");
+	if (max < 0)
+		return 0;
+
+	return max + 1;
+}
+
 int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 			       struct lock_class_key *lock_key,
 			       struct lock_class_key *request_key)
 {
+	int index, alias_id, min_idx;
 	struct fwnode_handle *fwnode = NULL;
 	struct gpio_device *gdev;
 	unsigned long flags;
@@ -696,12 +711,22 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 
 	device_set_node(&gdev->dev, gc->fwnode);
 
-	gdev->id = ida_alloc(&gpio_ida, GFP_KERNEL);
-	if (gdev->id < 0) {
-		ret = gdev->id;
-		goto err_free_gdev;
+	alias_id = of_alias_get_id(to_of_node(gc->fwnode), "gpio");
+	if (alias_id >= 0) {
+		index = ida_simple_get(&gpio_ida, alias_id, alias_id + 1,
+				       GFP_KERNEL);
+	} else {
+		min_idx = gpio_first_nonreserved_index();
+		index = ida_simple_get(&gpio_ida, min_idx, 0,
+				       GFP_KERNEL);
+		if (index < 0) {
+			ret = gdev->id;
+			goto err_free_gdev;
+		}
 	}
 
+	gdev->id = index;
+
 	ret = dev_set_name(&gdev->dev, GPIOCHIP_NAME "%d", gdev->id);
 	if (ret)
 		goto err_free_ida;
-- 
2.34.1