On Sun, 7 Oct 2007, Mauro Carvalho Chehab wrote:
> I took a look at cx23885 code. It seems that there's a serious error on
> the way you're using cx23885_buffer there:
>
> cx23885-dvb.c: return cx23885_buf_prepare(q, port, (struct
> cx23885_buffer*)vb, field);
> cx23885-dvb.c: cx23885_buf_queue(port, (struct cx23885_buffer*)vb);
> cx23885-dvb.c: cx23885_free_buffer(q, (struct cx23885_buffer*)vb);
>
> It seems that you are forcing videobuf_buffer to be cx23885_buffer. This
> is not right!
>
> This is what is defined on cx23885.h:
>
> struct cx23885_buffer {
> /* common v4l buffer stuff -- must be first */
> struct videobuf_buffer vb;
I'm not sure that it is competely wrong. Say one has a cx23885_buffer that
contains a videobuf_buffer. Now suppose you have a pointer to the
videobuf_buffer, and you want to get a pointer to the cx23885_buffer that
contains it. What you should write is:
struct videobuf_buffer *vb = ...;
struct cx23885_buffer *buf = container_of(vb, struct cx23885_buffer, vb);
But since vb is the first field of the cx23885_buffer struct, the container_of
will turn into just '(struct cx23885_buffer *)(vb)'
This code in videobuf-dma-sg.c looks odd to me:
/* Allocated area consists on 3 parts:
struct video_buffer
struct <driver>_buffer (cx88_buffer, saa7134_buf, ...)
struct videobuf_pci_sg_memory
static void *__videobuf_alloc(size_t size)
{
struct videbuf_pci_sg_memory *mem;
struct videobuf_buffer *vb;
vb = kzalloc(size+sizeof(*mem),GFP_KERNEL);
mem = vb->priv = ((char *)vb)+size;
What is 'size', is that the size of the driver buffer? Shouldn't you be
allocating size + sizeof(*vb) + sizeof(*mem)?
Is there documentation for videobuf anywhere? It doesn't look like any of
the videobuf functions have descriptions of that they do or what the
parameters are.
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