Re: [REVIEWv3 PATCH 09/13] vb2: add vb2_fileio_is_active and check it more often

[Tomasz Stanislawski <t.stanislaws@samsung.com>]

Hi Hans,

On 04/11/2014 10:11 AM, Hans Verkuil wrote:
> From: Hans Verkuil <hans.verkuil@cisco.com>
> 
> Added a vb2_fileio_is_active inline function that returns true if fileio
> is in progress. Check for this too in mmap() (you don't want apps mmap()ing
> buffers used by fileio) and expbuf() (same reason).

Why? I expect that there is no sane use case for using
mmap() and expbuf in read/write mode but why forbidding this.

Could you provide a reason?

Regard,
Tomasz Stanislawski

> 
> In addition drivers should be able to check for this in queue_setup() to
> return an error if an attempt is made to read() or write() with
> V4L2_FIELD_ALTERNATE being configured. This is illegal (there is no way
> to pass the TOP/BOTTOM information around using file I/O).
> 
> However, in order to be able to check for this the init_fileio function
> needs to set q->fileio early on, before the buffers are allocated. So switch
> to using internal functions (__reqbufs, vb2_internal_qbuf and
> vb2_internal_streamon) to skip the fileio check. Well, that's why the internal
> functions were created...
> 
> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> Acked-by: Pawel Osciak <pawel@osciak.com>
> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>