media: dmx-get-pes-pids.rst: document the ioctl

This ioctl is supported by the DVB core, but was never
documented.

Add a documentation for it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

diff --git a/Documentation/media/uapi/dvb/dmx-get-pes-pids.rst b/Documentation/media/uapi/dvb/dmx-get-pes-pids.rst
index 20288c11d2793ac2645046681e47d79a71a91fbd..fbdbc12869d1c7b88433e1226403df58944a510b 100644 (file)
--- a/Documentation/media/uapi/dvb/dmx-get-pes-pids.rst
+++ b/Documentation/media/uapi/dvb/dmx-get-pes-pids.rst
@@ -25,13 +25,31 @@ Arguments
     File descriptor returned by :c:func:`open() <dvb-dmx-open>`.
 
 ``pids``
-    Undocumented.
+    Array used to store 5 Program IDs.
 
 
 Description
 -----------
 
-.. note:: This ioctl is undocumented. Documentation is welcome.
+This ioctl allows to query a DVB device to return the first PID used
+by audio, video, textext, subtitle and PCR programs on a given service.
+They're stored as:
+
+=======================        ========        =======================================
+PID  element           position        content
+=======================        ========        =======================================
+pids[DMX_PES_AUDIO]    0               first audio PID
+pids[DMX_PES_VIDEO]    1               first video PID
+pids[DMX_PES_TELETEXT] 2               first teletext PID
+pids[DMX_PES_SUBTITLE] 3               first subtitle PID
+pids[DMX_PES_PCR]      4               first Program Clock Reference PID
+=======================        ========        =======================================
+
+
+.. note::
+
+       A value equal to 0xffff means that the PID was not filled by the
+       Kernel.
 
 
 Return Value