On 25.07.2015 09:11, Dirk Behme wrote:
The con_id parameter has to match the GPIO description and is automatically
extended by the GPIO suffix if not NULL. I had to look into the code to
understand this and properly find the GPIO I've been looking for, so document
this.
Signed-off-by: Dirk Behme <[email protected]>
---
Documentation/gpio/board.txt | 36 ++++++++++++++++++++++++++++++++++++
Documentation/gpio/consumer.txt | 3 +++
2 files changed, 39 insertions(+)
diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt
index 7605773..eac78fc 100644
--- a/Documentation/gpio/board.txt
+++ b/Documentation/gpio/board.txt
@@ -48,6 +48,42 @@ This property will make GPIOs 15, 16 and 17 available to the
driver under the
The led GPIOs will be active-high, while the power GPIO will be active-low
(i.e.
gpiod_is_active_low(power) will be true).
+If in the consumer device's node the property doesn't have a <function>-
prefix,
+the second parameter (con_id) of the gpiod_get*() functions has to be NULL:
+
+E.g. if in the above device tree example the GPIO array is just called 'gpios'
+
+ foo_device {
+ compatible = "acme,foo";
+ ...
+ gpios = <&gpio 15 GPIO_ACTIVE_HIGH>, /* red */
+ <&gpio 16 GPIO_ACTIVE_HIGH>, /* green */
+ <&gpio 17 GPIO_ACTIVE_HIGH>; /* blue */
+ };
+
+the gpiod_get*() calls will be:
+
+ struct gpio_desc *red, *green, *blue, *power;
+
+ red = gpiod_get_index(dev, NULL, 0, GPIOD_OUT_HIGH);
+ green = gpiod_get_index(dev, NULL, 1, GPIOD_OUT_HIGH);
+ blue = gpiod_get_index(dev, NULL, 2, GPIOD_OUT_HIGH);
+
+To summarize:
+
+The con_id string parameter has to be either NULL or the <function>-prefix
+of the GPIO suffixes ("gpios" or "gpio", automatically looked up by the
+gpiod functions internally):
+
+* If the GPIO description is just named with one of the GPIO suffixes
+ ("gpios" or "gpio"), use NULL.
+* If the GPIO description is prefixed with anything, e.g. "led-gpios", use the
+ prefix without the "-" as con_id parameter (in this example "led").
+
+In case con_id is not NULL, the GPIO subsystem prefixes the GPIO suffix
+("gpios" or "gpio") with the string passed in con_id to get the resulting
string
+(snprintf(... "%s-%s", con_id, gpio_suffixes[]).
+
ACPI
----
ACPI also supports function names for GPIOs in a similar fashion to DT.
diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt
index 75542b9..47ce4fd 100644
--- a/Documentation/gpio/consumer.txt
+++ b/Documentation/gpio/consumer.txt
@@ -39,6 +39,9 @@ device that displays digits), an additional index argument
can be specified:
const char *con_id, unsigned int idx,
enum gpiod_flags flags)
+For a more detailed description of the con_id parameter in the DeviceTree case
+see Documentation/gpio/board.txt
+
The flags parameter is used to optionally specify a direction and initial
value
for the GPIO. Values can be:
Any further comments on this? Or could this be applied?
Best regards
Dirk
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