V4L/DVB (5038): Pvrusb2: Implement stream claim checking function

Add (and expose) a new function, pvr2_channel_check_stream_no_lock(), in
pvrusb2-context.c. This is hopefully the last V4L2 interface related patch
to change anything outside pvrusb2-v4l2.c.

We need this to implement the open() for the radio device. The reason is
that within the *enter_context() section of open() we need to ensure nobody
is streaming and if we cannot, we should cleanup after ourselves and return
 -EBUSY. We cannot just use claim_stream() because:

   1) That would cause a deadlock trying to re-acquire the context lock
   2) We only need to ensure that nobody is streaming. We don't need to
      actually acquire the stream.

Again, this is a kinda ugly patch. Feel free to improve.

Signed-off-by: Pantelis Koukousoulas <pakt223@freemail.gr>
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

2 files changed, 13 insertions, 0 deletions

diff --git a/drivers/media/video/pvrusb2/pvrusb2-context.c b/drivers/media/video/pvrusb2/pvrusb2-context.c
index cf129746205d..69786cdaa859 100644
--- a/drivers/media/video/pvrusb2/pvrusb2-context.c
+++ b/drivers/media/video/pvrusb2/pvrusb2-context.c
@@ -188,6 +188,17 @@ void pvr2_channel_done(struct pvr2_channel *cp)
 }
 
 
+int pvr2_channel_check_stream_no_lock(struct pvr2_channel *cp,
+                              struct pvr2_context_stream *sp)
+{
+        if (sp == cp->stream) return 0;
+        if (sp->user) {
+                return -EBUSY;
+        }
+        return 0;
+}
+
+
 int pvr2_channel_claim_stream(struct pvr2_channel *cp,
                               struct pvr2_context_stream *sp)
 {
diff --git a/drivers/media/video/pvrusb2/pvrusb2-context.h b/drivers/media/video/pvrusb2/pvrusb2-context.h
index 6327fa1f7e4f..4d0f4ad64122 100644
--- a/drivers/media/video/pvrusb2/pvrusb2-context.h
+++ b/drivers/media/video/pvrusb2/pvrusb2-context.h
@@ -76,6 +76,8 @@ void pvr2_channel_init(struct pvr2_channel *,struct pvr2_context *);
 void pvr2_channel_done(struct pvr2_channel *);
 int pvr2_channel_claim_stream(struct pvr2_channel *,
                               struct pvr2_context_stream *);
+int pvr2_channel_check_stream_no_lock(struct pvr2_channel *,
+                              struct pvr2_context_stream *);
 struct pvr2_ioread *pvr2_channel_create_mpeg_stream(
         struct pvr2_context_stream *);