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>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index b73c39f998588388ed58bb10c5d376406572acc5..dbddace5df42d0a0ed60c043d2cf113d0f70d3ef 100644 (file)
--- 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)) {