[PATCH] gpiolib: have gpioinfo show line name if no label was set

[Ahmad Fatoum]

The upstream Linux bindings support an optional gpio-line-names for GPIO
controllers that can assign names to each GPIO of the controller.

In Linux userspace, utilities like gpiofind can be used to reference these
line-names. For barebox development purposes it can be nice to have the
line names printed when running gpioinfo to make finding the GPIO number
needed easier. populate a line_name gpio_desc member and print it when
using gpioinfo.

Signed-off-by: Ahmad Fatoum <a.fat...@pengutronix.de>
---
 drivers/gpio/gpiolib.c | 47 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f96009896a41..3c75c560b411 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -16,6 +16,7 @@ struct gpio_info {
        bool requested;
        bool active_low;
        char *label;
+       const char *line_name;
 };
 
 static struct gpio_info *gpio_desc;
@@ -434,6 +435,42 @@ static int of_gpiochip_scan_hogs(struct gpio_chip *chip)
        return 0;
 }
 
+/**
+ * of_gpiochip_set_names - Set GPIO line names using device properties
+ * @chip: GPIO chip whose lines should be named, if possible
+ * @np: device_node containing the gpio-line-names property
+ *
+ * Looks for device property "gpio-line-names" and if it exists assigns
+ * GPIO line names for the chip. The memory allocated for the assigned
+ * names belong to the underlying device tree node and should not be released
+ * by the caller.
+ */
+static void of_gpiochip_set_names(struct gpio_chip *chip,
+                                 struct device_node *np)
+{
+       int ret, i;
+       const char *name;
+       int count;
+
+       count = of_property_count_strings(np, "gpio-line-names");
+       if (count < 0)
+               return;
+
+       if (count > chip->ngpio)
+               count = chip->ngpio;
+
+       for (i = 0; i < count; i++) {
+               ret = of_property_read_string_index(np, "gpio-line-names",
+                                                   i, &name);
+               if (ret < 0) {
+                       dev_warn(chip->dev, "failed to read GPIO line names\n");
+                       return;
+               }
+
+               gpio_desc[chip->base + i].line_name = name;
+       }
+}
+
 int gpiochip_add(struct gpio_chip *chip)
 {
        int base, i;
@@ -452,6 +489,8 @@ int gpiochip_add(struct gpio_chip *chip)
        for (i = chip->base; i < chip->base + chip->ngpio; i++)
                gpio_desc[i].chip = chip;
 
+       of_gpiochip_set_names(chip, chip->dev->device_node);
+
        return of_gpiochip_scan_hogs(chip);
 }
 
@@ -490,6 +529,7 @@ static int do_gpiolib(int argc, char *argv[])
        for (i = 0; i < ARCH_NR_GPIOS; i++) {
                struct gpio_info *gi = &gpio_desc[i];
                int val = -1, dir = -1;
+               const char *name = "";
 
                if (!gi->chip)
                        continue;
@@ -510,11 +550,16 @@ static int do_gpiolib(int argc, char *argv[])
                        val = gi->chip->ops->get(gi->chip,
                                                i - gi->chip->base);
 
+               if (gi->requested && gi->label)
+                       name = gi->label;
+               else if (gi->line_name)
+                       name = gi->line_name;
+
                printf("  GPIO %*d: %*s %*s %*s  %s\n", 4, i,
                        3, (dir < 0) ? "unk" : ((dir == GPIOF_DIR_IN) ? "in" : 
"out"),
                        3, (val < 0) ? "unk" : ((val == 0) ? "lo" : "hi"),
                        12, gi->requested ? (gi->active_low ? "active low" : 
"true") : "false",
-                       (gi->requested && gi->label) ? gi->label : "");
+                       name);
        }
 
        return 0;
-- 
2.24.0


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