V4L/DVB (4090): Fix cinergyt2_poll() to allow non-blocking IO on frontend

cinergyt2_poll()" shouldn't return (POLLIN | POLLRDNORM | POLLPRI) when
there are no pending events. User space programs that do non-bocking IO
using "select()" and/or "poll()" would otherwise produce high system load.
Acked-by: Andreas Oberritter <obi@linuxtv.org>
Signed-off-by: Axel Dyks <xl@xlsigned.net>
Acked-by: Andreas Oberritter <obi@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

diff --git a/drivers/media/dvb/cinergyT2/cinergyT2.c b/drivers/media/dvb/cinergyT2/cinergyT2.c
index c7e4134..8cfdad6 100644 (file)
--- a/drivers/media/dvb/cinergyT2/cinergyT2.c
+++ b/drivers/media/dvb/cinergyT2/cinergyT2.c
@@ -544,15 +544,19 @@ static unsigned int cinergyt2_poll (struct file *file, struct poll_table_struct
 {
        struct dvb_device *dvbdev = file->private_data;
        struct cinergyt2 *cinergyt2 = dvbdev->priv;
+       unsigned int mask = 0;
 
        if (cinergyt2->disconnect_pending || mutex_lock_interruptible(&cinergyt2->sem))
                return -ERESTARTSYS;
 
        poll_wait(file, &cinergyt2->poll_wq, wait);
 
+       if (cinergyt2->pending_fe_events != 0)
+              mask |= (POLLIN | POLLRDNORM | POLLPRI);
+
        mutex_unlock(&cinergyt2->sem);
 
-       return (POLLIN | POLLRDNORM | POLLPRI);
+       return mask;
 }