Hi Laurent,
On 08/02/2013 03:03 AM, Laurent Pinchart wrote:
The VIDIOC_CREATE_BUFS ioctl takes a format argument that must contain a
valid format supported by the driver. Clarify the documentation.
Signed-off-by: Laurent Pinchart laurent.pinchart+rene...@ideasonboard.com
---
Documentation/DocBook/media/v4l/vidioc-create-bufs.xml | 15 ---
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml
b/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml
index cd99436..407937a 100644
--- a/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml
@@ -69,10 +69,11 @@ the structnamev4l2_create_buffers/structname
structure. They set the
structure, to the respective stream or buffer type.
structfieldcount/structfield must be set to the number of required
buffers.
structfieldmemory/structfield specifies the required I/O method. The
-structfieldformat/structfield field shall typically be filled in using
-either the constantVIDIOC_TRY_FMT/constant or
-constantVIDIOC_G_FMT/constant ioctl(). Additionally, applications can
adjust
-structfieldsizeimage/structfield fields to fit their specific needs. The
+structfieldformat/structfield field must be a valid format supported by
the
+driver. Applications shall typically fill it using either the
+constantVIDIOC_TRY_FMT/constant or constantVIDIOC_G_FMT/constant
+ioctl(). Any format that would be modified by the
+constantVIDIOC_TRY_FMT/constant ioctl() will be rejected with an error.
The
I'm a bit unhappy with this formulation. How about: The format must be a valid
format,
otherwise an error will be returned.
The main reason for this is that changes made to the 'field' and 'colorspace'
format
fields by TRY_FMT do not affect CREATE_BUFS. Does a wrong colorspace mean that
CREATE_BUFS should return an error? I'm not sure we want to do that, frankly.
You also removed the bit about the sizeimage field. That should be kept,
although admittedly
it needs some improvement. The reason for that is that applications cannot set
sizeimage
when calling S_FMT: that field is set by the driver. Only through CREATE_BUFS
can apps
select a different (larger) sizeimage.
I think it would be useful if there was a link to CREATE_BUFS was added to the
'sizeimage'
description of struct v4l2_pix_format in DocBook. It is not exactly obvious
that CREATE_BUFS
can be used for that purpose. It's really a workaround for a limitation in the
spec, of
course.
Regards,
Hans
structfieldreserved/structfield array must be zeroed./para
paraWhen the ioctl is called with a pointer to this structure the
driver
@@ -144,9 +145,9 @@ mapped/link I/O./para
varlistentry
termerrorcodeEINVAL/errorcode/term
listitem
- paraThe buffer type (structfieldtype/structfield field) or the
-requested I/O method (structfieldmemory/structfield) is not
-supported./para
+ paraThe buffer type (structfieldtype/structfield field),
+requested I/O method (structfieldmemory/structfield) or format
+(structfieldformat/structfield field) is not valid./para
/listitem
/varlistentry
/variablelist
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