Re: how to mmap in videobuf-dma-sg.c

["Figo.zhang" <figo1802@gmail.com>]

On Thu, 2009-05-21 at 07:35 -0300, Mauro Carvalho Chehab wrote:
> Em Thu, 21 May 2009 12:46:04 +0800
> "Figo.zhang" <figo1802@gmail.com> escreveu:
> 
> > hi,all,
> >  I am puzzle that how to mmap ( V4L2_MEMORY_MMAP) in videobuf-dma-sg.c?
> > 
> > In this file, it alloc the momery using vmalloc_32() , and put this
> > momery into sglist table,and then use dma_map_sg() to create sg dma at
> > __videobuf_iolock() function. but in __videobuf_mmap_mapper(), i canot
> > understand how it do the mmap? 
> > why it not use the remap_vmalloc_range() to do the mmap?
> 
> The answer is simple: remap_vmalloc_range() is newer than videobuf code. This
> part of the code was written back to kernel 2.4, and nobody cared to update it
> to use those newer functions, and simplify its code.
> 
> If you want, feel free to propose some cleanups on it
thanks, in __videobuf_mmap_mapper(), it define a videobuf_vm_ops->fault,
it
will alloc a new page for mmaping when it  encounter page fault
(do_page_fault),
so how the mmap() can mmap the vmalloc memory which had allocted before
using __videobuf_iolock()/vmalloc_
32() ?

Thanks,
Figo.zhang

> 
> 
> 
> Cheers,
> Mauro