[PATCH v3 3/7] gpiolib: Add support for GPIO line table lookup

[Geert Uytterhoeven <geert+renesas@glider.be>]

Currently GPIOs can only be referred to by GPIO controller and offset in
GPIO lookup tables.

Add support for looking them up by line name.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
If this is rejected, the GPIO Aggregator documentation and code must be
updated.

v3:
  - New.
---
 drivers/gpio/gpiolib.c       | 12 ++++++++++++
 include/linux/gpio/machine.h |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index d24a3d79dcfe69ad..cb608512ad6bbded 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -4475,6 +4475,18 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
 		if (p->con_id && (!con_id || strcmp(p->con_id, con_id)))
 			continue;
 
+		if (p->chip_hwnum == (u16)-1) {
+			desc = gpio_name_to_desc(p->chip_label);
+			if (desc) {
+				*flags = p->flags;
+				return desc;
+			}
+
+			dev_warn(dev, "cannot find GPIO line %s, deferring\n",
+				 p->chip_label);
+			return ERR_PTR(-EPROBE_DEFER);
+		}
+
 		chip = find_chip_by_name(p->chip_label);
 
 		if (!chip) {
diff --git a/include/linux/gpio/machine.h b/include/linux/gpio/machine.h
index 1ebe5be05d5f81fa..84c1c097e55eefaf 100644
--- a/include/linux/gpio/machine.h
+++ b/include/linux/gpio/machine.h
@@ -31,7 +31,7 @@ enum gpio_lookup_flags {
  */
 struct gpiod_lookup {
 	const char *chip_label;
-	u16 chip_hwnum;
+	u16 chip_hwnum;			/* if -1, chip_label is named line */
 	const char *con_id;
 	unsigned int idx;
 	unsigned long flags;
-- 
2.17.1