[PATCH] gpio: Add gpio_request_by_line_name()

[Andrew Jeffery]

Add support for the upstream gpio-line-names property already described
in the common GPIO binding document[1]. The ability to search for a line
name allows boards to lift the implementation of common GPIO behaviours
away from specific line indexes on a GPIO controller.

[1] https://github.com/devicetree-org/dt-schema/blob/3c35bfee83c2e38e2ae7af5f83eb89ca94a521e8/dtschema/schemas/gpio/gpio.yaml#L17

Signed-off-by: Andrew Jeffery <andrew at aj.id.au>
---
Hi,

This patch is extracted from and motivated by a series adding run-time
control of FIT signature verification to u-boot in OpenBMC:

https://lore.kernel.org/openbmc/20220131012538.73021-1-andrew@aj.id.au/

Unfortunately the OpenBMC u-boot tree is quite a way behind on tracking
upstream and contains a bunch of out-of-tree work as well. As such I'm
looking to upstream the couple of changes that make sense against
master.

Please take a look!

Andrew

 drivers/gpio/gpio-uclass.c | 26 ++++++++++++++++++++++++++
 include/asm-generic/gpio.h | 19 +++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/drivers/gpio/gpio-uclass.c b/drivers/gpio/gpio-uclass.c
index 125ae53d612f..be00a1f7d871 100644
--- a/drivers/gpio/gpio-uclass.c
+++ b/drivers/gpio/gpio-uclass.c
@@ -1187,6 +1187,32 @@ int gpio_request_by_name(struct udevice *dev, const char *list_name, int index,
 				 index, desc, flags, index > 0, NULL);
 }
 
+int gpio_request_by_line_name(struct udevice *dev, const char *line_name,
+			      struct gpio_desc *desc, int flags)
+{
+	int ret;
+
+	ret = dev_read_stringlist_search(dev, "gpio-line-names", line_name);
+	if (ret < 0)
+		return ret;
+
+	desc->dev = dev;
+	desc->offset = ret;
+	desc->flags = 0;
+
+	ret = dm_gpio_request(desc, line_name);
+	if (ret) {
+		debug("%s: dm_gpio_requestf failed\n", __func__);
+		return ret;
+	}
+
+	ret = dm_gpio_set_dir_flags(desc, flags | desc->flags);
+	if (ret)
+		debug("%s: dm_gpio_set_dir failed\n", __func__);
+
+	return ret;
+}
+
 int gpio_request_list_by_name_nodev(ofnode node, const char *list_name,
 				    struct gpio_desc *desc, int max_count,
 				    int flags)
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index adc19e9765d7..81f63f06f15e 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -579,6 +579,25 @@ int gpio_claim_vector(const int *gpio_num_array, const char *fmt);
 int gpio_request_by_name(struct udevice *dev, const char *list_name,
 			 int index, struct gpio_desc *desc, int flags);
 
+/* gpio_request_by_line_name - Locate and request a GPIO by line name
+ *
+ * Request a GPIO using the offset of the provided line name in the
+ * gpio-line-names property found in the OF node of the GPIO udevice.
+ *
+ * This allows boards to implement common behaviours using GPIOs while not
+ * requiring specific GPIO offsets be used.
+ *
+ * @dev:	An instance of a GPIO controller udevice
+ * @line_name:	The name of the GPIO (e.g. "bmc-secure-boot")
+ * @desc:	A GPIO descriptor that is populated with the requested GPIO
+ *              upon return
+ * @flags:	The GPIO settings apply to the request
+ * @return 0 if the named line was found and requested successfully, or a
+ * negative error code if the GPIO cannot be found or the request failed.
+ */
+int gpio_request_by_line_name(struct udevice *dev, const char *line_name,
+			      struct gpio_desc *desc, int flags);
+
 /**
  * gpio_request_list_by_name() - Request a list of GPIOs
  *
-- 
2.32.0