| Message ID | 20231003080704.43911-2-benjamin.gaignard@collabora.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Add DELETE_BUF ioctl | expand |
Hi Benjamin, On 03/10/2023 10:06, Benjamin Gaignard wrote: > Change how offset 'cookie' field value is computed to make possible > to use more buffers. > The maximum number of buffers depends of PAGE_SHIFT value and can > go up to 0x7fff when PAGE_SHIFT = 12. > With this encoding pattern we know the maximum number that a queue > could store so we can check it at queue init time. > It also make easier and faster to find buffer and plane from using > the offset field. > Change __find_plane_by_offset() prototype to return the video buffer > itself rather than it index. > > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com> > --- > changes in version 10: > - Make BUFFER_INDEX_MASK definition more readable. > - Correct typo. > > .../media/common/videobuf2/videobuf2-core.c | 72 +++++++++---------- > 1 file changed, 33 insertions(+), 39 deletions(-) > > diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c > index 27aee92f3eea..5591ac830668 100644 > --- a/drivers/media/common/videobuf2/videobuf2-core.c > +++ b/drivers/media/common/videobuf2/videobuf2-core.c > @@ -31,6 +31,11 @@ > > #include <trace/events/vb2.h> > > +#define PLANE_INDEX_SHIFT (PAGE_SHIFT + 3) > +#define PLANE_INDEX_MASK 0x7 > +#define MAX_BUFFER_INDEX BIT_MASK(30 - PLANE_INDEX_SHIFT) > +#define BUFFER_INDEX_MASK (MAX_BUFFER_INDEX - 1) > + > static int debug; > module_param(debug, int, 0644); > > @@ -358,21 +363,24 @@ static void __setup_offsets(struct vb2_buffer *vb) > unsigned int plane; > unsigned long off = 0; This is a rather ugly name. I suggest renaming this to "offset" to avoid confusion with "on"/"off". See additional comments on this below. > > - if (vb->index) { > - struct vb2_buffer *prev = q->bufs[vb->index - 1]; > - struct vb2_plane *p = &prev->planes[prev->num_planes - 1]; > - > - off = PAGE_ALIGN(p->m.offset + p->length); > - } > + /* > + * Offsets cookies value have the following constraints: I'd rephrase this a little bit: * The offset "cookie" value has the following constraints: > + * - a buffer can have up to 8 planes. > + * - v4l2 mem2mem uses bit 30 to distinguish between source and destination buffers. Related to Sakari's comments: the mem2mem framework uses source and destination a lot, but vb2 is mostly OUTPUT/CAPTURE. So it is best to mention both: source -> OUTPUT (aka "source", bit 30 is 0) destination -> CAPTURE (aka "destination", bit 30 is 1) > + * - must be page aligned > + * That led to this bit mapping when PAGE_SHIFT = 12: > + * |30 |29 15|14 12|11 0| > + * |DST_QUEUE_OFF_BASE|buffer index|plane index| 0 | > + * where there are 15 bits to store the buffer index. > + * Depending on PAGE_SHIFT value we can have fewer bits to store the buffer index. > + */ > + off = vb->index << PLANE_INDEX_SHIFT; > > for (plane = 0; plane < vb->num_planes; ++plane) { > - vb->planes[plane].m.offset = off; > + vb->planes[plane].m.offset = off + (plane << PAGE_SHIFT); > > dprintk(q, 3, "buffer %d, plane %d offset 0x%08lx\n", > vb->index, plane, off); > - > - off += vb->planes[plane].length; > - off = PAGE_ALIGN(off); > } > } > > @@ -2185,13 +2193,12 @@ int vb2_core_streamoff(struct vb2_queue *q, unsigned int type) > EXPORT_SYMBOL_GPL(vb2_core_streamoff); > > /* > - * __find_plane_by_offset() - find plane associated with the given offset off > + * __find_plane_by_offset() - find video buffer and plane associated with the given offset off > */ > static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off, Same here: rename "off" to "offset", that also simplifies the comment above: "with the given offset off" can now just be "with the given offset". The same change can be done in vb2_mmap and vb2_get_unmapped_area. I think it would be best if the off -> offset rename is done in a separate initial patch. I know that this isn't really DELETE_BUFS related, but I think it makes the code a bit easier to follow. > - unsigned int *_buffer, unsigned int *_plane) > + struct vb2_buffer **vb, unsigned int *plane) > { > - struct vb2_buffer *vb; > - unsigned int buffer, plane; > + unsigned int buffer; > > /* > * Sanity checks to ensure the lock is held, MEMORY_MMAP is > @@ -2209,24 +2216,15 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off, > return -EBUSY; > } > > - /* > - * Go over all buffers and their planes, comparing the given offset > - * with an offset assigned to each plane. If a match is found, > - * return its buffer and plane numbers. > - */ > - for (buffer = 0; buffer < q->num_buffers; ++buffer) { > - vb = q->bufs[buffer]; > + /* Get buffer and plane from the offset */ > + buffer = (off >> PLANE_INDEX_SHIFT) & BUFFER_INDEX_MASK; > + *plane = (off >> PAGE_SHIFT) & PLANE_INDEX_MASK; > > - for (plane = 0; plane < vb->num_planes; ++plane) { > - if (vb->planes[plane].m.offset == off) { > - *_buffer = buffer; > - *_plane = plane; > - return 0; > - } > - } > - } > + if (buffer >= q->num_buffers || *plane >= q->bufs[buffer]->num_planes) > + return -EINVAL; > > - return -EINVAL; > + *vb = q->bufs[buffer]; > + return 0; > } > > int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type, > @@ -2306,7 +2304,7 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) > { > unsigned long off = vma->vm_pgoff << PAGE_SHIFT; > struct vb2_buffer *vb; > - unsigned int buffer = 0, plane = 0; > + unsigned int plane = 0; > int ret; > unsigned long length; > > @@ -2335,12 +2333,10 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) > * Find the plane corresponding to the offset passed by userspace. This > * will return an error if not MEMORY_MMAP or file I/O is in progress. > */ > - ret = __find_plane_by_offset(q, off, &buffer, &plane); > + ret = __find_plane_by_offset(q, off, &vb, &plane); > if (ret) > goto unlock; > > - vb = q->bufs[buffer]; > - > /* > * MMAP requires page_aligned buffers. > * The buffer length was page_aligned at __vb2_buf_mem_alloc(), > @@ -2368,7 +2364,7 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) > if (ret) > return ret; > > - dprintk(q, 3, "buffer %d, plane %d successfully mapped\n", buffer, plane); > + dprintk(q, 3, "buffer %u, plane %d successfully mapped\n", vb->index, plane); > return 0; > } > EXPORT_SYMBOL_GPL(vb2_mmap); > @@ -2382,7 +2378,7 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q, > { > unsigned long off = pgoff << PAGE_SHIFT; > struct vb2_buffer *vb; > - unsigned int buffer, plane; > + unsigned int plane; > void *vaddr; > int ret; > > @@ -2392,12 +2388,10 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q, > * Find the plane corresponding to the offset passed by userspace. This > * will return an error if not MEMORY_MMAP or file I/O is in progress. > */ > - ret = __find_plane_by_offset(q, off, &buffer, &plane); > + ret = __find_plane_by_offset(q, off, &vb, &plane); > if (ret) > goto unlock; > > - vb = q->bufs[buffer]; > - > vaddr = vb2_plane_vaddr(vb, plane); > mutex_unlock(&q->mmap_lock); > return vaddr ? (unsigned long)vaddr : -EINVAL; Regards, Hans
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c index 27aee92f3eea..5591ac830668 100644 --- a/drivers/media/common/videobuf2/videobuf2-core.c +++ b/drivers/media/common/videobuf2/videobuf2-core.c @@ -31,6 +31,11 @@ #include <trace/events/vb2.h> +#define PLANE_INDEX_SHIFT (PAGE_SHIFT + 3) +#define PLANE_INDEX_MASK 0x7 +#define MAX_BUFFER_INDEX BIT_MASK(30 - PLANE_INDEX_SHIFT) +#define BUFFER_INDEX_MASK (MAX_BUFFER_INDEX - 1) + static int debug; module_param(debug, int, 0644); @@ -358,21 +363,24 @@ static void __setup_offsets(struct vb2_buffer *vb) unsigned int plane; unsigned long off = 0; - if (vb->index) { - struct vb2_buffer *prev = q->bufs[vb->index - 1]; - struct vb2_plane *p = &prev->planes[prev->num_planes - 1]; - - off = PAGE_ALIGN(p->m.offset + p->length); - } + /* + * Offsets cookies value have the following constraints: + * - a buffer can have up to 8 planes. + * - v4l2 mem2mem uses bit 30 to distinguish between source and destination buffers. + * - must be page aligned + * That led to this bit mapping when PAGE_SHIFT = 12: + * |30 |29 15|14 12|11 0| + * |DST_QUEUE_OFF_BASE|buffer index|plane index| 0 | + * where there are 15 bits to store the buffer index. + * Depending on PAGE_SHIFT value we can have fewer bits to store the buffer index. + */ + off = vb->index << PLANE_INDEX_SHIFT; for (plane = 0; plane < vb->num_planes; ++plane) { - vb->planes[plane].m.offset = off; + vb->planes[plane].m.offset = off + (plane << PAGE_SHIFT); dprintk(q, 3, "buffer %d, plane %d offset 0x%08lx\n", vb->index, plane, off); - - off += vb->planes[plane].length; - off = PAGE_ALIGN(off); } } @@ -2185,13 +2193,12 @@ int vb2_core_streamoff(struct vb2_queue *q, unsigned int type) EXPORT_SYMBOL_GPL(vb2_core_streamoff); /* - * __find_plane_by_offset() - find plane associated with the given offset off + * __find_plane_by_offset() - find video buffer and plane associated with the given offset off */ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off, - unsigned int *_buffer, unsigned int *_plane) + struct vb2_buffer **vb, unsigned int *plane) { - struct vb2_buffer *vb; - unsigned int buffer, plane; + unsigned int buffer; /* * Sanity checks to ensure the lock is held, MEMORY_MMAP is @@ -2209,24 +2216,15 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off, return -EBUSY; } - /* - * Go over all buffers and their planes, comparing the given offset - * with an offset assigned to each plane. If a match is found, - * return its buffer and plane numbers. - */ - for (buffer = 0; buffer < q->num_buffers; ++buffer) { - vb = q->bufs[buffer]; + /* Get buffer and plane from the offset */ + buffer = (off >> PLANE_INDEX_SHIFT) & BUFFER_INDEX_MASK; + *plane = (off >> PAGE_SHIFT) & PLANE_INDEX_MASK; - for (plane = 0; plane < vb->num_planes; ++plane) { - if (vb->planes[plane].m.offset == off) { - *_buffer = buffer; - *_plane = plane; - return 0; - } - } - } + if (buffer >= q->num_buffers || *plane >= q->bufs[buffer]->num_planes) + return -EINVAL; - return -EINVAL; + *vb = q->bufs[buffer]; + return 0; } int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type, @@ -2306,7 +2304,7 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) { unsigned long off = vma->vm_pgoff << PAGE_SHIFT; struct vb2_buffer *vb; - unsigned int buffer = 0, plane = 0; + unsigned int plane = 0; int ret; unsigned long length; @@ -2335,12 +2333,10 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) * Find the plane corresponding to the offset passed by userspace. This * will return an error if not MEMORY_MMAP or file I/O is in progress. */ - ret = __find_plane_by_offset(q, off, &buffer, &plane); + ret = __find_plane_by_offset(q, off, &vb, &plane); if (ret) goto unlock; - vb = q->bufs[buffer]; - /* * MMAP requires page_aligned buffers. * The buffer length was page_aligned at __vb2_buf_mem_alloc(), @@ -2368,7 +2364,7 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) if (ret) return ret; - dprintk(q, 3, "buffer %d, plane %d successfully mapped\n", buffer, plane); + dprintk(q, 3, "buffer %u, plane %d successfully mapped\n", vb->index, plane); return 0; } EXPORT_SYMBOL_GPL(vb2_mmap); @@ -2382,7 +2378,7 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q, { unsigned long off = pgoff << PAGE_SHIFT; struct vb2_buffer *vb; - unsigned int buffer, plane; + unsigned int plane; void *vaddr; int ret; @@ -2392,12 +2388,10 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q, * Find the plane corresponding to the offset passed by userspace. This * will return an error if not MEMORY_MMAP or file I/O is in progress. */ - ret = __find_plane_by_offset(q, off, &buffer, &plane); + ret = __find_plane_by_offset(q, off, &vb, &plane); if (ret) goto unlock; - vb = q->bufs[buffer]; - vaddr = vb2_plane_vaddr(vb, plane); mutex_unlock(&q->mmap_lock); return vaddr ? (unsigned long)vaddr : -EINVAL;
Change how offset 'cookie' field value is computed to make possible to use more buffers. The maximum number of buffers depends of PAGE_SHIFT value and can go up to 0x7fff when PAGE_SHIFT = 12. With this encoding pattern we know the maximum number that a queue could store so we can check it at queue init time. It also make easier and faster to find buffer and plane from using the offset field. Change __find_plane_by_offset() prototype to return the video buffer itself rather than it index. Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com> --- changes in version 10: - Make BUFFER_INDEX_MASK definition more readable. - Correct typo. .../media/common/videobuf2/videobuf2-core.c | 72 +++++++++---------- 1 file changed, 33 insertions(+), 39 deletions(-)