This is a standard ioctl supported by file descriptors, sockets (as
SIOCINQ), and ttys (as TIOCOUTQ) to get the size of the available
read buffer. It provides userspace with a feedback mechanism to
avoid overflow of the kernel ringbuffer, and is used by e.g.
libevent.
Signed-off-by: Dominic Chen <d.c.ddcc@xxxxxxxxx>
---
drivers/media/dvb-core/dmxdev.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/drivers/media/dvb-core/dmxdev.c b/drivers/media/dvb-core/dmxdev.c
index a168cbe..668c8d2 100644
--- a/drivers/media/dvb-core/dmxdev.c
+++ b/drivers/media/dvb-core/dmxdev.c
@@ -28,6 +28,7 @@
#include <linux/poll.h>
#include <linux/ioctl.h>
#include <linux/wait.h>
+#include <asm/ioctls.h>
#include <asm/uaccess.h>
#include "dmxdev.h"
@@ -57,6 +58,22 @@ static int dvb_dmxdev_buffer_write(struct dvb_ringbuffer *buf,
return dvb_ringbuffer_write(buf, src, len);
}
+static int dvb_dmxdev_get_buffer_avail(struct dvb_ringbuffer *src,
+ u32 *len)
+{
+ if (!src->data) {
+ *len = 0;
+ return 0;
+ }
+
+ if (src->error)
+ return src->error;
+
+ *len = dvb_ringbuffer_avail(src);
+
+ return 0;
+}
+
static ssize_t dvb_dmxdev_buffer_read(struct dvb_ringbuffer *src,
int non_blocking, char __user *buf,
size_t count, loff_t *ppos)
@@ -965,6 +982,16 @@ static int dvb_demux_do_ioctl(struct file *file,
return -ERESTARTSYS;
switch (cmd) {
+ case FIONREAD:
+ if (mutex_lock_interruptible(&dmxdevfilter->mutex)) {
+ mutex_unlock(&dmxdev->mutex);
+ return -ERESTARTSYS;
+ }
+ ret = dvb_dmxdev_get_buffer_avail(&dmxdevfilter->buffer, parg);
+ mutex_unlock(&dmxdevfilter->mutex);
+
+ break;
+
case DMX_START:
if (mutex_lock_interruptible(&dmxdevfilter->mutex)) {
mutex_unlock(&dmxdev->mutex);
@@ -1160,6 +1187,10 @@ static int dvb_dvr_do_ioctl(struct file *file,
return -ERESTARTSYS;
switch (cmd) {
+ case FIONREAD:
+ ret = dvb_dmxdev_get_buffer_avail(&dmxdev->dvr_buffer, parg);
+ break;
+
case DMX_SET_BUFFER_SIZE:
ret = dvb_dvr_set_buffer_size(dmxdev, arg);
break;
--
2.7.4
--
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