gpiolib: use platform GPIO mappings as fallback

For platforms that use device tree or ACPI as the standard way to look
GPIOs up, allow the platform-defined GPIO mappings to be used as a
fallback. This may be useful for platforms that need extra GPIOs mappings
not defined by the firmware.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 13 insertions, 3 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index b73c39f99858..dbddace5df42 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2418,7 +2418,7 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
                                                const char *con_id,
                                                unsigned int idx)
 {
-        struct gpio_desc *desc;
+        struct gpio_desc *desc = NULL;
         int status;
         enum gpio_lookup_flags flags = 0;
 
@@ -2431,9 +2431,19 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
         } else if (IS_ENABLED(CONFIG_ACPI) && dev && ACPI_HANDLE(dev)) {
                 dev_dbg(dev, "using ACPI for GPIO lookup\n");
                 desc = acpi_find_gpio(dev, con_id, idx, &flags);
-        } else {
+        }
+
+        /*
+         * Either we are not using DT or ACPI, or their lookup did not return
+         * a result. In that case, use platform lookup as a fallback.
+         */
+        if (!desc || IS_ERR(desc)) {
+                struct gpio_desc *pdesc;
                 dev_dbg(dev, "using lookup tables for GPIO lookup");
-                desc = gpiod_find(dev, con_id, idx, &flags);
+                pdesc = gpiod_find(dev, con_id, idx, &flags);
+                /* If used as fallback, do not replace the previous error */
+                if (!IS_ERR(pdesc) || !desc)
+                        desc = pdesc;
         }
 
         if (IS_ERR(desc)) {