mirror of https://gitee.com/openkylin/linux.git
V4L/DVB (7494): videobuf-dma-sg.c: Avoid NULL dereference and add comment about backwards compatibility
Signed-off-by: Brandon Philips <bphilips@suse.de> Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
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@ -546,6 +546,14 @@ static int __videobuf_mmap_mapper(struct videobuf_queue *q,
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goto done;
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}
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/* This function maintains backwards compatibility with V4L1 and will
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* map more than one buffer if the vma length is equal to the combined
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* size of multiple buffers than it will map them together. See
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* VIDIOCGMBUF in the v4l spec
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*
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* TODO: Allow drivers to specify if they support this mode
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*/
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/* look for first buffer to map */
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for (first = 0; first < VIDEO_MAX_FRAME; first++) {
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if (NULL == q->bufs[first])
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@ -590,10 +598,16 @@ static int __videobuf_mmap_mapper(struct videobuf_queue *q,
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map = kmalloc(sizeof(struct videobuf_mapping),GFP_KERNEL);
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if (NULL == map)
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goto done;
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for (size = 0, i = first; i <= last; size += q->bufs[i++]->bsize) {
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size = 0;
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for (i = first; i <= last; i++) {
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if (NULL == q->bufs[i])
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continue;
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q->bufs[i]->map = map;
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q->bufs[i]->baddr = vma->vm_start + size;
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size += q->bufs[i]->bsize;
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}
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map->count = 1;
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map->start = vma->vm_start;
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map->end = vma->vm_end;
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