[PATCH v3 2/3] gpio: search gpio-line-names property in dm_gpio_lookup_name

[Rasmus Villemoes <ravi@prevas.dk>]

In scripts as well as interactively, it's much nicer to be able to
refer to GPIOs via their names defined in the device tree property
"gpio-line-names", instead of the rather opaque names derived from the
bank name with a _xx suffix. E.g.

  gpio read factory_reset FACTORY_RESET
  if test $factory_reset = 1 ; then ...

versus

  gpio read factory_reset gpio@481ac000_16
  if test $factory_reset = 1 ; then ...

This is also consistent with the move on the linux/userspace side towards
using line names instead of legacy chip+offset or the even more legacy
global gpio numbering in sysfs.

As dev_read_stringlist_search() depends on both OF_CONTROL and
OF_LIBFDT (which matters for the SPL case), we need some .config
conditional. However, it only adds about ~50 bytes of code to U-Boot
proper, and dm_gpio_lookup_name() most often ends up being GC'ed for
SPL, thus adds no overhead there, so for now make it a hidden symbol
which is merely a convenient shorthand for
CONFIG_IS_ENABLED(OF_CONTROL) && CONFIG_IS_ENABLED(OF_LIBFDT).

Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
---
 drivers/gpio/Kconfig       | 16 ++++++++++++++++
 drivers/gpio/gpio-uclass.c | 11 ++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index db077e472a8..a47c127d98c 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -97,6 +97,22 @@ config SPL_DM_GPIO_LOOKUP_LABEL
 	  different gpios on different hardware versions
 	  for the same functionality in board code.
 
+config DM_GPIO_LOOKUP_LINE_NAME
+	def_bool y
+	depends on OF_CONTROL && OF_LIBFDT
+	help
+	  This option enables specifying a GPIO by referring to its
+	  name as defined by the "gpio-line-names" property in the
+	  gpio controller's devicetree node.
+
+config SPL_DM_GPIO_LOOKUP_LINE_NAME
+	def_bool y
+	depends on SPL_OF_CONTROL && SPL_OF_LIBFDT
+	help
+	  This option enables specifying a GPIO by referring to its
+	  name as defined by the "gpio-line-names" property in the
+	  gpio controller's devicetree node.
+
 config ADI_GPIO
 	bool "ADI GPIO driver"
 	depends on DM_GPIO && ARCH_SC5XX
diff --git a/drivers/gpio/gpio-uclass.c b/drivers/gpio/gpio-uclass.c
index 3d9f8b32b8d..6f52fdf4ef4 100644
--- a/drivers/gpio/gpio-uclass.c
+++ b/drivers/gpio/gpio-uclass.c
@@ -164,7 +164,7 @@ int dm_gpio_lookup_name(const char *name, struct gpio_desc *desc)
 	for (uclass_first_device(UCLASS_GPIO, &dev);
 	     dev;
 	     uclass_next_device(&dev)) {
-		int len;
+		int len, ret;
 
 		uc_priv = dev_get_uclass_priv(dev);
 		if (numeric != -1) {
@@ -188,6 +188,15 @@ int dm_gpio_lookup_name(const char *name, struct gpio_desc *desc)
 		 */
 		if (!dm_gpio_lookup_label(name, uc_priv, &offset))
 			break;
+
+		/* Also search the "gpio-line-names" property in DT for a match. */
+		if (CONFIG_IS_ENABLED(DM_GPIO_LOOKUP_LINE_NAME)) {
+			ret = dev_read_stringlist_search(dev, "gpio-line-names", name);
+			if (ret >= 0) {
+				offset = ret;
+				break;
+			}
+		}
 	}
 
 	if (!dev)
-- 
2.51.0