On Sat, Jan 18, 2014 at 12:47 AM, Arnd Bergmann [off-list ref] wrote:

On Friday 17 January 2014, Chen-Yu Tsai wrote:

quoted

diff --git a/Documentation/devicetree/bindings/rfkill/rfkill-gpio.txt b/Documentation/devicetree/bindings/rfkill/rfkill-gpio.txt
new file mode 100644
index 0000000..8a07ea4
--- /dev/null
+++ b/Documentation/devicetree/bindings/rfkill/rfkill-gpio.txt

@@ -0,0 +1,26 @@
+GPIO controlled RFKILL devices
+
+Required properties:
+- compatible   : Must be "rfkill-gpio".
+- rfkill-name  : Name of RFKILL device
+- rfkill-type  : Type of RFKILL device: 1 for WiFi, 2 for BlueTooth
+- NAME_shutdown-gpios  : GPIO phandle to shutdown control
+                         (phandle must be the second)
+- NAME_reset-gpios     : GPIO phandle to reset control
+
+NAME must match the rfkill-name property. NAME_shutdown-gpios or
+NAME_reset-gpios, or both, must be defined.
+

I don't understand this part. Why do you include the name in the
gpios property, rather than just hardcoding the property strings
to "shutdown-gpios" and "reset-gpios"?

This quirk is a result of how gpiod_get_index implements device tree
lookup. You'll also notice that the shutdown GPIO must be the second
phandle, as the driver uses indexed lookup to support ACPI cases.
If con_id is given, it is prepended to "gpios" as the property string.
con_id is also used as the label passed to gpiod_request, which is
then shown in /sys/kernel/debug/gpio.

I can do a seperate lookup for the device tree case, with or without
fallback to platform lookup tables. Then the names can be "reset-gpio"
and "shutdown-gpio". Need to promote gpiod_request to non-static so
we can register usage of the gpio, to match non-dt code path.

Personally I prefer adding a "label" parameter to gpiod_get_index, so
we can use a different name than con_id. con_id isn't used in the ACPI
case, and is optional in platform lookup case. However device tree
lookup is dependent on this. What I see is non-uniform behavior
between the three. In my opinion this is undesirable, but I haven't
come up with a good solution yet.

About the property string, is the plural form required, even though we
only want one?

Thanks!

ChenYu

The description of hte "rfkill-name" property seems to suggest
that you can only have one logical RFKILL device per device node,
so he names would not be ambiguous.

        Arnd