[RFC,04/10] DocBook: make the G/S/TRY_FMT specification more strict.

Commit Message

Hans Verkuil Sept. 3, 2012, 1:48 p.m. UTC

From: Hans Verkuil <[e-mail]>

- S/TRY_FMT should always succeed, unless an invalid type field is passed in.
- TRY_FMT should give the same result as S_FMT, all other things being equal.
- ENUMFMT may return different formats for different inputs or outputs.

This was decided during the 2012 Media Workshop.

Signed-off-by: Hans Verkuil <[e-mail]>
---
 Documentation/DocBook/media/v4l/vidioc-enum-fmt.xml |    3 +++
 Documentation/DocBook/media/v4l/vidioc-g-fmt.xml    |    9 ++++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

Patch

diff --git a/Documentation/DocBook/media/v4l/vidioc-enum-fmt.xml b/Documentation/DocBook/media/v4l/vidioc-enum-fmt.xml
index 81ebe48..0bd3324 100644
--- a/Documentation/DocBook/media/v4l/vidioc-enum-fmt.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-enum-fmt.xml
@@ -58,6 +58,9 @@  structure. Drivers fill the rest of the structure or return an
 incrementing by one until <errorcode>EINVAL</errorcode> is
 returned.</para>
 
+    <para>Note that after switching input or output the list of enumerated image
+formats may be different.</para>
+
     <table pgwide="1" frame="none" id="v4l2-fmtdesc">
       <title>struct <structname>v4l2_fmtdesc</structname></title>
       <tgroup cols="3">
diff --git a/Documentation/DocBook/media/v4l/vidioc-g-fmt.xml b/Documentation/DocBook/media/v4l/vidioc-g-fmt.xml
index 52acff1..9ef279a 100644
--- a/Documentation/DocBook/media/v4l/vidioc-g-fmt.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-g-fmt.xml
@@ -81,7 +81,7 @@  the application calls the <constant>VIDIOC_S_FMT</constant> ioctl
 with a pointer to a <structname>v4l2_format</structname> structure
 the driver checks
 and adjusts the parameters against hardware abilities. Drivers
-should not return an error code unless the input is ambiguous, this is
+should not return an error code unless the <structfield>type</structfield> field is invalid, this is
 a mechanism to fathom device capabilities and to approach parameters
 acceptable for both the application and driver. On success the driver
 may program the hardware, allocate resources and generally prepare for
@@ -107,6 +107,10 @@  disabling I/O or possibly time consuming hardware preparations.
 Although strongly recommended drivers are not required to implement
 this ioctl.</para>
 
+    <para>The format as returned by <constant>VIDIOC_TRY_FMT</constant>
+must be identical to what <constant>VIDIOC_S_FMT</constant> returns for
+the same input or output.</para>
+
     <table pgwide="1" frame="none" id="v4l2-format">
       <title>struct <structname>v4l2_format</structname></title>
       <tgroup cols="4">
@@ -187,8 +191,7 @@  capture and output devices.</entry>
 	<term><errorcode>EINVAL</errorcode></term>
 	<listitem>
 	  <para>The &v4l2-format; <structfield>type</structfield>
-field is invalid, the requested buffer type not supported, or the
-format is not supported with this buffer type.</para>
+field is invalia or the requested buffer type not supported.</para>
 	</listitem>
       </varlistentry>
     </variablelist>