[media] vb2: add vb2_fileio_is_active and check it more often

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).

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>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index af4621109726..b1859f6953b2 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -472,6 +472,23 @@ static inline bool vb2_is_streaming(struct vb2_queue *q)
 }
 
 /**
+ * vb2_fileio_is_active() - return true if fileio is active.
+ * @q:          videobuf queue
+ *
+ * This returns true if read() or write() is used to stream the data
+ * as opposed to stream I/O. This is almost never an important distinction,
+ * except in rare cases. One such case is that using read() or write() to
+ * stream a format using V4L2_FIELD_ALTERNATE is not allowed since there
+ * is no way you can pass the field information of each buffer to/from
+ * userspace. A driver that supports this field format should check for
+ * this in the queue_setup op and reject it if this function returns true.
+ */
+static inline bool vb2_fileio_is_active(struct vb2_queue *q)
+{
+        return q->fileio;
+}
+
+/**
  * vb2_is_busy() - return busy status of the queue
  * @q:          videobuf queue
  *