[PATCH v2] gpio: of: Support SPI nonstandard GPIO properties

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

Before it was clearly established that all GPIO properties in the
device tree shall be named "foo-gpios" (with the deprecated variant
"foo-gpio" for single lines) we unfortunately merged a few bindings
which named the lines "gpio-foo" instead.

This is most prominent in the GPIO SPI driver in Linux which names
the lines "gpio-sck", "gpio-mosi" and "gpio-miso".

As we want to switch the GPIO SPI driver to using descriptors, we
need devm_gpiod_get() to return something reasonable when looking
up these in the device tree.

Put in a special #ifdef:ed kludge to do this special lookup only
for the SPI case and gets compiled out if we're not enabling SPI.
If we have more oddly defined legacy GPIOs like this, they can be
handled in a similar manner.

Cc: Rob Herring <robh@xxxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
I will merge this into the GPIO tree as a preparation for the next
(v4.17) kernel cycle so that we avoid cross-tree dependencies.
I estimate that it is too late to merge the bulk of the patches
for v4.16, but this can go in.

ChangeLog v1->v2:
- Us if IS_ENABLED(CONFIG_SPI_MASTER) instead of
  #ifdef CONFIG_SPI_MASTER
---
 drivers/gpio/gpiolib-of.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index e0d59e61b52f..3ae9876e8c44 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -117,6 +117,37 @@ int of_get_named_gpio_flags(struct device_node *np, const char *list_name,
 }
 EXPORT_SYMBOL(of_get_named_gpio_flags);
 
+/*
+ * The SPI GPIO bindings happened before we managed to establish that GPIO
+ * properties should be named "foo-gpios" so we have this special kludge for
+ * them.
+ */
+#if IS_ENABLED(CONFIG_SPI_MASTER)
+static struct gpio_desc *of_find_spi_gpio(struct device *dev, const char *con_id,
+					  enum of_gpio_flags *of_flags)
+{
+	char prop_name[32]; /* 32 is max size of property name */
+	struct device_node *np = dev->of_node;
+	struct gpio_desc *desc;
+
+	/* Allow this specifically for "spi-gpio" devices */
+	if (!of_device_is_compatible(np, "spi-gpio") || !con_id)
+		return ERR_PTR(-ENOENT);
+
+	/* Will be "gpio-sck", "gpio-mosi" or "gpio-miso" */
+	snprintf(prop_name, sizeof(prop_name), "%s-%s", "gpio", con_id);
+
+	desc = of_get_named_gpiod_flags(np, prop_name, 0, of_flags);
+	return desc;
+}
+#else
+static struct gpio_desc *of_find_spi_gpio(struct device *dev, const char *con_id,
+					  enum of_gpio_flags *of_flags)
+{
+	return ERR_PTR(-ENOENT);
+}
+#endif
+
 struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
 			       unsigned int idx,
 			       enum gpio_lookup_flags *flags)
@@ -126,6 +157,7 @@ struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
 	struct gpio_desc *desc;
 	unsigned int i;
 
+	/* Try GPIO property "foo-gpios" and "foo-gpio" */
 	for (i = 0; i < ARRAY_SIZE(gpio_suffixes); i++) {
 		if (con_id)
 			snprintf(prop_name, sizeof(prop_name), "%s-%s", con_id,
@@ -140,6 +172,10 @@ struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
 			break;
 	}
 
+	/* Special handling for SPI GPIOs if used */
+	if (IS_ERR(desc))
+		desc = of_find_spi_gpio(dev, con_id, &of_flags);
+
 	if (IS_ERR(desc))
 		return desc;
 
-- 
2.14.3

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