gpio: of: make it possible to name GPIO lines
Make it possible to name the producer side of a GPIO line using
a "gpio-line-names" property array, modeled on the
"clock-output-names" property from the clock bindings.
This naming is especially useful for:
- Debugging: lines are named after function, not just opaque
offset numbers.
- Exploration: systems where some or all GPIO lines are available
to end users, such as prototyping, one-off's "makerspace usecases"
users are helped by the names of the GPIO lines when tinkering.
This usecase has been surfacing recently.
The gpio-line-names attribute is completely optional.
Example output from lsgpio on a patched Snowball tree:
GPIO chip: gpiochip6, "8000e180.gpio", 32 GPIO lines
line 0: unnamed unused
line 1: "AP_GPIO161" "extkb3" [kernel]
line 2: "AP_GPIO162" "extkb4" [kernel]
line 3: "ACCELEROMETER_INT1_RDY" unused [kernel]
line 4: "ACCELEROMETER_INT2" unused
line 5: "MAG_DRDY" unused [kernel]
line 6: "GYRO_DRDY" unused [kernel]
line 7: "RSTn_MLC" unused
line 8: "RSTn_SLC" unused
line 9: "GYRO_INT" unused
line 10: "UART_WAKE" unused
line 11: "GBF_RESET" unused
line 12: unnamed unused
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: David Mandala <david.mandala@linaro.org>
Cc: Lee Campbell <leecam@google.com>
Cc: devicetree@vger.kernel.org
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Michael Welling <mwelling@ieee.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index d81dbd8..d22dcc3 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -196,6 +196,51 @@
}
/**
+ * of_gpiochip_set_names() - set up the names of the lines
+ * @chip: GPIO chip whose lines should be named, if possible
+ */
+static void of_gpiochip_set_names(struct gpio_chip *gc)
+{
+ struct gpio_device *gdev = gc->gpiodev;
+ struct device_node *np = gc->of_node;
+ int i;
+ int nstrings;
+
+ nstrings = of_property_count_strings(np, "gpio-line-names");
+ if (nstrings <= 0)
+ /* Lines names not present */
+ return;
+
+ /* This is normally not what you want */
+ if (gdev->ngpio != nstrings)
+ dev_info(&gdev->dev, "gpio-line-names specifies %d line "
+ "names but there are %d lines on the chip\n",
+ nstrings, gdev->ngpio);
+
+ /*
+ * Make sure to not index beyond the end of the number of descriptors
+ * of the GPIO device.
+ */
+ for (i = 0; i < gdev->ngpio; i++) {
+ const char *name;
+ int ret;
+
+ ret = of_property_read_string_index(np,
+ "gpio-line-names",
+ i,
+ &name);
+ if (ret) {
+ if (ret != -ENODATA)
+ dev_err(&gdev->dev,
+ "unable to name line %d: %d\n",
+ i, ret);
+ break;
+ }
+ gdev->descs[i].name = name;
+ }
+}
+
+/**
* of_gpiochip_scan_gpios - Scan gpio-controller for gpio definitions
* @chip: gpio chip to act on
*
@@ -445,6 +490,10 @@
if (status)
return status;
+ /* If the chip defines names itself, these take precedence */
+ if (!chip->names)
+ of_gpiochip_set_names(chip);
+
of_node_get(chip->of_node);
return of_gpiochip_scan_gpios(chip);