V4L/DVB (7194): cx88-mpeg: Allow concurrent access to cx88-mpeg devices

It currently isn't possible to open the frontend device of cx88-mpeg devices
(DVB or Blackbird) multiple times concurrently. (for instance, to attach a
signal monitoring tool while reading a stream, or to send a frequency change
ioctl) This patch fixes that condition.

Signed-off-by: Roland Stoll <roland@xindex.de>
Signed-off-by: Ricardo Cerqueira <v4l@cerqueira.org>
Reviewed-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 12 insertions, 4 deletions

diff --git a/drivers/media/video/cx88/cx88-mpeg.c b/drivers/media/video/cx88/cx88-mpeg.c
index 0aedbeaf94cd..f12733d6bf72 100644
--- a/drivers/media/video/cx88/cx88-mpeg.c
+++ b/drivers/media/video/cx88/cx88-mpeg.c
@@ -609,13 +609,19 @@ static int cx8802_request_acquire(struct cx8802_driver *drv)
         struct cx88_core *core = drv->core;
 
         /* Fail a request for hardware if the device is busy. */
-        if (core->active_type_id != CX88_BOARD_NONE)
+        if (core->active_type_id != CX88_BOARD_NONE &&
+            core->active_type_id != drv->type_id)
                 return -EBUSY;
 
         if (drv->advise_acquire)
         {
-                core->active_type_id = drv->type_id;
-                drv->advise_acquire(drv);
+                core->active_ref++;
+                mutex_lock(&drv->core->lock);
+                if (core->active_type_id == CX88_BOARD_NONE) {
+                        core->active_type_id = drv->type_id;
+                        drv->advise_acquire(drv);
+                }
+                mutex_unlock(&drv->core->lock);
 
                 mpeg_dbg(1,"%s() Post acquire GPIO=%x\n", __FUNCTION__, cx_read(MO_GP0_IO));
         }
@@ -628,10 +634,12 @@ static int cx8802_request_release(struct cx8802_driver *drv)
 {
         struct cx88_core *core = drv->core;
 
-        if (drv->advise_release)
+        if (drv->advise_release && --core->active_ref == 0)
         {
+                mutex_lock(&drv->core->lock);
                 drv->advise_release(drv);
                 core->active_type_id = CX88_BOARD_NONE;
+                mutex_unlock(&drv->core->lock);
                 mpeg_dbg(1,"%s() Post release GPIO=%x\n", __FUNCTION__, cx_read(MO_GP0_IO));
         }