Documentation: gpio: describe uAPI behaviour for unsupported config

The existing uAPI documentation does not adequately describe how the kernel
handles the case where the underlying hardware or driver does not support
the requested configuration.

Add a Configuration Support section describing that behaviour to both the
v1 and v2 documentation, and better document the errors returned where the
requested configuration cannot be supported.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/Documentation/userspace-api/gpio/gpio-handle-set-config-ioctl.rst b/Documentation/userspace-api/gpio/gpio-handle-set-config-ioctl.rst
index 8f1e748dccc8..d002a84681ac 100644
--- a/Documentation/userspace-api/gpio/gpio-handle-set-config-ioctl.rst
+++ b/Documentation/userspace-api/gpio/gpio-handle-set-config-ioctl.rst
@@ -41,12 +41,13 @@ line or introducing potential glitches.
 
 The configuration applies to all requested lines.
 
-The same :ref:`gpio-get-linehandle-config-rules` that apply when requesting the
+The same :ref:`gpio-get-linehandle-config-rules` and
+:ref:`gpio-get-linehandle-config-support` that apply when requesting the
 lines also apply when updating the line configuration.
 
 The motivating use case for this command is changing direction of
 bi-directional lines between input and output, but it may be used more
-generally move lines seamlessly from one configuration state to another.
+generally to move lines seamlessly from one configuration state to another.
 
 To only change the value of output lines, use
 gpio-handle-set-line-values-ioctl.rst.