pvrusb2: Implement stream claim checking function

From: Pantelis Koukousoulas <pakt223@freemail.gr>

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>

2 files changed, 13 insertions, 0 deletions

diff --git a/linux/drivers/media/video/pvrusb2/pvrusb2-context.c b/linux/drivers/media/video/pvrusb2/pvrusb2-context.c
index 19787dc81..6ad1ce7dc 100644
--- a/linux/drivers/media/video/pvrusb2/pvrusb2-context.c
+++ b/linux/drivers/media/video/pvrusb2/pvrusb2-context.c
@@ -205,6 +205,17 @@ 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/linux/drivers/media/video/pvrusb2/pvrusb2-context.h b/linux/drivers/media/video/pvrusb2/pvrusb2-context.h
index 69c1f3a92..5e960ae51 100644
--- a/linux/drivers/media/video/pvrusb2/pvrusb2-context.h
+++ b/linux/drivers/media/video/pvrusb2/pvrusb2-context.h
@@ -85,6 +85,8 @@ 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 *);