Re: [Linaro-mm-sig] [RFCv2 PATCH 4/9] v4l: add buffer exporting via dmabuf

On Thu, Mar 22, 2012 at 03:07:18PM +0100, Laurent Pinchart wrote:

...

...

...

• • Contains data used for exporting a video buffer as DMABUF file
• • descriptor. Uses the same 'cookie' as mmap() syscall. All reserved

fields

• • must be set to zero.
• */

+struct v4l2_exportbuffer {

• __u32 fd;
• __u32 reserved0;

Why is there a reserved field here ?

+1 to Laurent. Any particular need for reserved0 and reserved[13] below? I think one void user pointer is sufficient even for future need.

I'd rather have more than one void user pointer, just in case. A couple of bytes won't be expensive, and they will save lots of hassle in the future if we need to add a couple of fields. I was just wondering why there was a reserved field between fd and mem_offset.

Quick comment from a random bystander: __u32 is not big enough for a void* pointer from userspace ... -Daniel