Hi,
I see that in current videobuf library, for DMA SG code, these functions fail when
Detecting a page in Highmem region:
- videobuf_pages_to_sg
- videobuf_vmalloc_to_sg
Now, what's the real reason to not allow handling of Highmem pages?
Is it an assumption that _always_ HighMem is not reachable by DMA?
I guess my point is, OMAP platform (and maybe other platforms) can handle
Highmem pages without any problem. I commented these validations:
65 static struct scatterlist *videobuf_vmalloc_to_sg(unsigned char *virt,
66 int nr_pages)
67 {
...
77 for (i = 0; i < nr_pages; i++, virt += PAGE_SIZE) {
78 pg = vmalloc_to_page(virt);
79 if (NULL == pg)
80 goto err;
81 /* BUG_ON(PageHighMem(pg)); */
...
96 static struct scatterlist *videobuf_pages_to_sg(struct page **pages,
97 int nr_pages, int offset)
98 {
...
109 /* if (PageHighMem(pages[0])) */
110 /* DMA to highmem pages might not work */
111 /* goto highmem; */
112 sg_set_page(&sglist[0], pages[0], PAGE_SIZE - offset, offset);
113 for (i = 1; i < nr_pages; i++) {
114 if (NULL == pages[i])
115 goto nopage;
116 /* if (PageHighMem(pages[i]))
117 goto highmem; */
118 sg_set_page(&sglist[i], pages[i], PAGE_SIZE, 0);
119 }
Can somebody shed any light on this?
Regards,
Sergio
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