Messages in this thread | | | Date | Wed, 8 Nov 2023 11:14:32 +0100 | Subject | Re: [PATCH v14 02/56] media: videobuf2: Rework offset 'cookie' encoding pattern | From | Benjamin Gaignard <> |
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Le 08/11/2023 à 07:23, Tomasz Figa a écrit : > Hi Benjamin, > > On Tue, Oct 31, 2023 at 05:30:10PM +0100, 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> >> --- >> .../media/common/videobuf2/videobuf2-core.c | 73 +++++++++---------- >> 1 file changed, 35 insertions(+), 38 deletions(-) >> > Thanks a lot for working on this series. Just one comment inline. > >> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c >> index a5e57affeb30..09be8e026044 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 > Could we somehow ensure that it indeed matches VIDEO_MAX_PLANES? > > One thing that comes to my mind would be > > #define PLANE_INDEX_BITS 3 > #define PLANE_INDEX_SHIFT (PAGE_SHIFT + PLANE_INDEX_BITS) > #define PLANE_INDEX_MASK BIT_MASK(PLANE_INDEX_BITS) > > BUILD_BUG_ON(BIT(PLANE_INDEX_BITS) != VIDEO_MAX_PLANES); > > Alternatively we could change the videodev2.h, so that we have > > #define VIDEO_MAX_PLANES_BITS 3 > #define VIDEO_MAX_PLANES (1U < VIDEO_MAX_PLANES_BITS) > > and then we can just VIDEO_MAX_PLANES_BITS in our definitions in this file > and no checks would be necessary.
I would prefer this solution. Hans should I do that in an other patch ?
Regards, Benjamin
> > Best regards, > Tomasz > >> +#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 +363,27 @@ static void __setup_offsets(struct vb2_buffer *vb) >> unsigned int plane; >> unsigned long offset = 0; >> >> - if (vb->index) { >> - struct vb2_buffer *prev = q->bufs[vb->index - 1]; >> - struct vb2_plane *p = &prev->planes[prev->num_planes - 1]; >> - >> - offset = PAGE_ALIGN(p->m.offset + p->length); >> - } >> + /* >> + * The offset "cookie" value has the following constraints: >> + * - a buffer can have up to 8 planes. >> + * - v4l2 mem2mem uses bit 30 to distinguish between >> + * OUTPUT (aka "source", bit 30 is 0) and >> + * CAPTURE (aka "destination", bit 30 is 1) 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. >> + */ >> + offset = vb->index << PLANE_INDEX_SHIFT; >> >> for (plane = 0; plane < vb->num_planes; ++plane) { >> - vb->planes[plane].m.offset = offset; >> + vb->planes[plane].m.offset = offset + (plane << PAGE_SHIFT); >> >> dprintk(q, 3, "buffer %d, plane %d offset 0x%08lx\n", >> vb->index, plane, offset); >> - >> - offset += vb->planes[plane].length; >> - offset = PAGE_ALIGN(offset); >> } >> } >> >> @@ -2188,10 +2199,9 @@ EXPORT_SYMBOL_GPL(vb2_core_streamoff); >> * __find_plane_by_offset() - find plane associated with the given offset >> */ >> static int __find_plane_by_offset(struct vb2_queue *q, unsigned long offset, >> - 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 +2219,15 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long offset, >> 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 = (offset >> PLANE_INDEX_SHIFT) & BUFFER_INDEX_MASK; >> + *plane = (offset >> PAGE_SHIFT) & PLANE_INDEX_MASK; >> >> - for (plane = 0; plane < vb->num_planes; ++plane) { >> - if (vb->planes[plane].m.offset == offset) { >> - *_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 +2307,7 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) >> { >> unsigned long offset = 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 +2336,10 @@ 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, offset, &buffer, &plane); >> + ret = __find_plane_by_offset(q, offset, &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 +2367,7 @@ 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 +2381,7 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q, >> { >> unsigned long offset = pgoff << PAGE_SHIFT; >> struct vb2_buffer *vb; >> - unsigned int buffer, plane; >> + unsigned int plane; >> void *vaddr; >> int ret; >> >> @@ -2392,12 +2391,10 @@ 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, offset, &buffer, &plane); >> + ret = __find_plane_by_offset(q, offset, &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; >> -- >> 2.39.2 >>
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