Oliver Endriss wrote:
- With your code the demux becomes unusable if the memory allocation
failes for some reason. This should be avoided. It is better have a
working demux with a smaller buffer than to have an defunct demux.
- If there is not enough memory for both buffers, your machine has a problem
anyway, and you should not increase buffer size.
> ....
I'm sorry, spin_lock_irqsave/spin_unlock_irqrestore was a typo.
We have to use spin_[un]lock_irq because buffer writing _might_ occur
in interrupt context. So the '_irq' is very important!
Ok.
I've changed the second patch to
1) allocate the new buffer before releasing the old one
2) use spin_[un]lock_irq
3) On top of that, I have rearranged the code of DMX_SET_BUFFER_SIZE for the demux so that it does
the same as the dvr (i.e. allocate the new buffer before releasing the old one). I think it is a
good idea that 2 very similar functions are implemented in the same way. (if you don't agree, or if
you think a 3rd separate patch for this point is a better idea, let me know.)
PS: Both patches 1/3 and 2/3 are against a clean v4l-dvb tree. I do not know how to generate
incremental patch for 2/3.
Let me know what you think about that.
Andrea
diff -r 54cdcd915a6b linux/drivers/media/dvb/dvb-core/dmxdev.c
--- a/linux/drivers/media/dvb/dvb-core/dmxdev.c Fri Apr 11 08:29:44 2008 -0300
+++ b/linux/drivers/media/dvb/dvb-core/dmxdev.c Sun Apr 13 10:14:54 2008 +0100
@@ -259,6 +259,39 @@ static ssize_t dvb_dvr_read(struct file
return ret;
}
+static int dvb_dvr_set_buffer_size(struct dmxdev *dmxdev,
+ unsigned long size)
+{
+ struct dvb_ringbuffer *buf = &dmxdev->dvr_buffer;
+ void *newmem;
+ void *oldmem;
+
+ dprintk("function : %s\n", __FUNCTION__);
+
+ if (buf->size == size)
+ return 0;
+ if (!size)
+ return -EINVAL;
+
+ newmem = vmalloc(size);
+ if (!newmem)
+ return -ENOMEM;
+
+ oldmem = buf->data;
+
+ spin_lock_irq(&dmxdev->lock);
+ buf->data = newmem;
+ buf->size = size;
+
+ // reset and not flush in case the buffer shrinks
+ dvb_ringbuffer_reset(buf);
+ spin_unlock_irq(&dmxdev->lock);
+
+ vfree(oldmem);
+
+ return 0;
+}
+
static inline void dvb_dmxdev_filter_state_set(struct dmxdev_filter
*dmxdevfilter, int state)
{
@@ -271,28 +304,32 @@ static int dvb_dmxdev_set_buffer_size(st
unsigned long size)
{
struct dvb_ringbuffer *buf = &dmxdevfilter->buffer;
- void *mem;
+ void *newmem;
+ void *oldmem;
if (buf->size == size)
return 0;
+ if (!size)
+ return -EINVAL;
if (dmxdevfilter->state >= DMXDEV_STATE_GO)
return -EBUSY;
+
+ newmem = vmalloc(size);
+ if (!newmem)
+ return -ENOMEM;
+
+ oldmem = buf->data;
+
spin_lock_irq(&dmxdevfilter->dev->lock);
- mem = buf->data;
- buf->data = NULL;
+ buf->data = newmem;
buf->size = size;
- dvb_ringbuffer_flush(buf);
+
+ // reset and not flush, in case the new buffer is smaller
+ dvb_ringbuffer_reset(buf);
spin_unlock_irq(&dmxdevfilter->dev->lock);
- vfree(mem);
-
- if (buf->size) {
- mem = vmalloc(dmxdevfilter->buffer.size);
- if (!mem)
- return -ENOMEM;
- spin_lock_irq(&dmxdevfilter->dev->lock);
- buf->data = mem;
- spin_unlock_irq(&dmxdevfilter->dev->lock);
- }
+
+ vfree(oldmem);
+
return 0;
}
@@ -1009,6 +1046,7 @@ static int dvb_dvr_do_ioctl(struct inode
{
struct dvb_device *dvbdev = file->private_data;
struct dmxdev *dmxdev = dvbdev->priv;
+ unsigned long arg = (unsigned long)parg;
int ret;
if (mutex_lock_interruptible(&dmxdev->mutex))
@@ -1016,8 +1054,7 @@ static int dvb_dvr_do_ioctl(struct inode
switch (cmd) {
case DMX_SET_BUFFER_SIZE:
- // FIXME: implement
- ret = 0;
+ ret = dvb_dvr_set_buffer_size(dmxdev, arg);
break;
default:
diff -r 54cdcd915a6b linux/drivers/media/dvb/dvb-core/dvb_ringbuffer.c
--- a/linux/drivers/media/dvb/dvb-core/dvb_ringbuffer.c Fri Apr 11 08:29:44 2008 -0300
+++ b/linux/drivers/media/dvb/dvb-core/dvb_ringbuffer.c Sun Apr 13 10:14:54 2008 +0100
@@ -90,6 +90,11 @@ void dvb_ringbuffer_flush(struct dvb_rin
rbuf->error = 0;
}
+void dvb_ringbuffer_reset(struct dvb_ringbuffer *rbuf)
+{
+ rbuf->pread = rbuf->pwrite = 0;
+ rbuf->error = 0;
+}
void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer *rbuf)
diff -r 54cdcd915a6b linux/drivers/media/dvb/dvb-core/dvb_ringbuffer.h
--- a/linux/drivers/media/dvb/dvb-core/dvb_ringbuffer.h Fri Apr 11 08:29:44 2008 -0300
+++ b/linux/drivers/media/dvb/dvb-core/dvb_ringbuffer.h Sun Apr 13 10:14:54 2008 +0100
@@ -84,6 +84,12 @@ extern ssize_t dvb_ringbuffer_free(struc
/* return the number of bytes waiting in the buffer */
extern ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf);
+/*
+** Reset the read and write pointers to zero and flush the buffer
+** This counts as a read and write operation
+*/
+
+extern void dvb_ringbuffer_reset(struct dvb_ringbuffer *rbuf);
/* read routines & macros */
/* ---------------------- */
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