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Message-ID: <AM6PR04MB634195FDE919FA9462187045E7BE9@AM6PR04MB6341.eurprd04.prod.outlook.com>
Date: Tue, 14 Mar 2023 02:10:55 +0000
From: Ming Qian <ming.qian@....com>
To: Benjamin Gaignard <benjamin.gaignard@...labora.com>,
"tfiga@...omium.org" <tfiga@...omium.org>,
"m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
"mchehab@...nel.org" <mchehab@...nel.org>,
"shijie.qin@....com" <shijie.qin@....com>,
Eagle Zhou <eagle.zhou@....com>,
"bin.liu@...iatek.com" <bin.liu@...iatek.com>,
"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
"angelogioacchino.delregno@...labora.com"
<angelogioacchino.delregno@...labora.com>,
"tiffany.lin@...iatek.com" <tiffany.lin@...iatek.com>,
"andrew-ct.chen@...iatek.com" <andrew-ct.chen@...iatek.com>,
"yunfei.dong@...iatek.com" <yunfei.dong@...iatek.com>,
"stanimir.k.varbanov@...il.com" <stanimir.k.varbanov@...il.com>,
"quic_vgarodia@...cinc.com" <quic_vgarodia@...cinc.com>,
"agross@...nel.org" <agross@...nel.org>,
"andersson@...nel.org" <andersson@...nel.org>,
"konrad.dybcio@...aro.org" <konrad.dybcio@...aro.org>,
"ezequiel@...guardiasur.com.ar" <ezequiel@...guardiasur.com.ar>,
"p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
"daniel.almeida@...labora.com" <daniel.almeida@...labora.com>,
"hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>,
"laurent.pinchart@...asonboard.com"
<laurent.pinchart@...asonboard.com>,
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CC: "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-mediatek@...ts.infradead.org"
<linux-mediatek@...ts.infradead.org>,
"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
"linux-rockchip@...ts.infradead.org"
<linux-rockchip@...ts.infradead.org>,
"kernel@...labora.com" <kernel@...labora.com>
Subject: RE: [EXT] [RFC 3/4] media: videobuf2: Use bitmap to manage vb2 index
>Using a bitmap to get vb2 index will allow to avoid holes in the indexes when
>introducing DELETE_BUF ioctl.
>
>Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
>---
> .../media/common/videobuf2/videobuf2-core.c | 22 ++++++++++++++++++-
> include/media/videobuf2-core.h | 6 +++++
> 2 files changed, 27 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
>b/drivers/media/common/videobuf2/videobuf2-core.c
>index 96597d339a07..3554811ec06a 100644
>--- a/drivers/media/common/videobuf2/videobuf2-core.c
>+++ b/drivers/media/common/videobuf2/videobuf2-core.c
>@@ -397,6 +397,22 @@ static void init_buffer_cache_hints(struct vb2_queue
>*q, struct vb2_buffer *vb)
> vb->skip_cache_sync_on_finish = 1; }
>
>+/*
>+ * __vb2_get_index() - find a free index in the queue for vb2 buffer.
>+ *
>+ * Returns an index for vb2 buffer.
>+ */
>+static int __vb2_get_index(struct vb2_queue *q) {
>+ unsigned long index;
>+
>+ index = bitmap_find_next_zero_area(q->bmap, q->idx_max, 0, 1, 0);
>+ if (index > q->idx_max)
>+ dprintk(q, 1, "no index available for buffer\n");
>+
>+ return index;
>+}
>+
> /*
> * __vb2_queue_alloc() - allocate vb2 buffer structures and (for MMAP type)
> * video buffer memory for all buffers/planes on the queue and initializes the
>@@ -423,7 +439,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q,
>enum vb2_memory memory,
> vb->state = VB2_BUF_STATE_DEQUEUED;
> vb->vb2_queue = q;
> vb->num_planes = num_planes;
>- vb->index = q->num_buffers + buffer;
>+ vb->index = __vb2_get_index(q);
> vb->type = q->type;
> vb->memory = memory;
> init_buffer_cache_hints(q, vb); @@ -2438,6 +2454,9 @@ int
>vb2_core_queue_init(struct vb2_queue *q)
> mutex_init(&q->mmap_lock);
> init_waitqueue_head(&q->done_wq);
>
>+ q->idx_max = ALIGN(256, BITS_PER_LONG);
>+ q->bmap = bitmap_zalloc(q->idx_max, GFP_KERNEL);
>+
Hi Benjamin,
Does it mean the maximum vb2 buffer count is enlarged to 256?
What will happen if user create the 257th buffer?
Ming
> q->memory = VB2_MEMORY_UNKNOWN;
>
> if (q->buf_struct_size == 0)
>@@ -2465,6 +2484,7 @@ void vb2_core_queue_release(struct vb2_queue *q)
> mutex_lock(&q->mmap_lock);
> __vb2_queue_free(q, q->num_buffers);
> mutex_unlock(&q->mmap_lock);
>+ bitmap_free(q->bmap);
> }
> EXPORT_SYMBOL_GPL(vb2_core_queue_release);
>
>diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-
>core.h index 47f1f35eb9cb..4fddc6ae9f20 100644
>--- a/include/media/videobuf2-core.h
>+++ b/include/media/videobuf2-core.h
>@@ -561,6 +561,8 @@ struct vb2_buf_ops {
> * @dma_dir: DMA mapping direction.
> * @allocated_bufs: list of buffer allocated for the queue.
> * @num_buffers: number of allocated/used buffers
>+ * @bmap: Bitmap of buffers index
>+ * @idx_max: number of bits in bmap
> * @queued_list: list of buffers currently queued from userspace
> * @queued_count: number of buffers queued and ready for streaming.
> * @owned_by_drv_count: number of buffers owned by the driver @@ -
>624,6 +626,8 @@ struct vb2_queue {
> enum dma_data_direction dma_dir;
> struct list_head allocated_bufs;
> unsigned int num_buffers;
>+ unsigned long *bmap;
>+ int idx_max;
>
> struct list_head queued_list;
> unsigned int queued_count;
>@@ -1259,6 +1263,7 @@ static inline struct vb2_buffer
>*vb2_get_buffer(struct vb2_queue *q, static inline void vb2_set_buffer(struct
>vb2_queue *q, struct vb2_buffer *vb) {
> list_add_tail(&vb->allocated_entry, &q->allocated_bufs);
>+ __set_bit(vb->index, q->bmap);
> }
>
> /**
>@@ -1268,6 +1273,7 @@ static inline void vb2_set_buffer(struct vb2_queue
>*q, struct vb2_buffer *vb)
> */
> static inline void vb2_del_buffer(struct vb2_queue *q, struct vb2_buffer *vb)
>{
>+ __clear_bit(vb->index, q->bmap);
> list_del(&vb->allocated_entry);
> }
>
>--
>2.34.1
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