[PATCH 3/4] Documentation: gpio: Reconfiguration with unset direction (uAPI v1)

[Kent Gibson <warthog618@gmail.com>]

Update description of reconfiguration rules, adding requirement that a
direction flag be set or the configuration is considered invalid.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
---
 .../userspace-api/gpio/gpio-handle-set-config-ioctl.rst      | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

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 d002a84681ac..a03f30db63ab 100644
--- a/Documentation/userspace-api/gpio/gpio-handle-set-config-ioctl.rst
+++ b/Documentation/userspace-api/gpio/gpio-handle-set-config-ioctl.rst
@@ -43,7 +43,10 @@ The configuration applies to all requested lines.
 
 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.
+lines also apply when updating the line configuration, with the additional
+restriction that a direction flag must be set. Requesting an invalid
+configuration, including without a direction flag set, is an error
+(**EINVAL**).
 
 The motivating use case for this command is changing direction of
 bi-directional lines between input and output, but it may be used more
-- 
2.39.2