Hi Mauro, On Monday 26 September 2011 15:30:15 Mauro Carvalho Chehab wrote: > Em 26-09-2011 08:21, Marek Szyprowski escreveu: > > On Monday, September 26, 2011 1:14 PM Mauro Carvalho Chehab wrote: > >>> Scott Jiang (1): > >>> vb2: add vb2_get_unmapped_area in vb2 core > >>> > >>> diff --git a/include/media/videobuf2-core.h > >>> b/include/media/videobuf2-core.h index ea55c08..977410b 100644 > >>> --- a/include/media/videobuf2-core.h > >>> +++ b/include/media/videobuf2-core.h > >>> @@ -309,6 +309,13 @@ int vb2_streamon(struct vb2_queue *q, enum > >>> v4l2_buf_type type); > >>> > >>> int vb2_streamoff(struct vb2_queue *q, enum v4l2_buf_type type); > >>> > >>> int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma); > >>> > >>> +#ifndef CONFIG_MMU > >>> +unsigned long vb2_get_unmapped_area(struct vb2_queue *q, > >>> + unsigned long addr, > >>> + unsigned long len, > >>> + unsigned long pgoff, > >>> + unsigned long flags); > >>> +#endif > >>> > >>> unsigned int vb2_poll(struct vb2_queue *q, struct file *file, > >>> poll_table *wait); size_t vb2_read(struct vb2_queue *q, char __user > >>> *data, size_t count, > >>> > >>> loff_t *ppos, int nonblock); > >> > >> This sounds me like a hack, as it is passing the problem of working with > >> a non-mmu capable hardware to the driver, inserting > >> architecture-dependent bits on them. > >> > >> The proper way to do it is to provide a vb2 core support to handle the > >> non-mmu case inside it. > > > > This is exactly what this patch does - it provides generic vb2 > > implementation for fops->get_unmapped_area callback which any vb2 ready > > driver can use. This operation is used only on NON-MMU systems. Please > > check drivers/media/video/v4l2-dev.c file and the implementation of > > get_unmapped_area there. Similar code is used by uvc driver. > > At least there, there is a: > #ifdef CONFIG_MMU > #define v4l2_get_unmapped_area NULL > #else > ... > #endif > > block, so, in thesis, a driver can be written to support both cases without > inserting #ifdefs inside it. > > Ideally, I would prefer if all those iommu-specific calls would be inside > the core. A driver should not need to do anything special in order to > support a different (sub)architecture. Just for the sake of correctness, this is about no-mmu systems, not about iommus. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
