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Message-ID: <c927dccb-9915-38dc-a522-f3d4a9755abf@xs4all.nl>
Date:   Thu, 31 Aug 2023 12:22:04 +0200
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Subject: Re: [PATCH v5 02/10] media: videobuf2: Access vb2_queue bufs array
 through helper functions
Content-Language: en-US, nl
To:     Benjamin Gaignard <benjamin.gaignard@collabora.com>,
        mchehab@kernel.org, tfiga@chromium.org, m.szyprowski@samsung.com,
        ming.qian@nxp.com, ezequiel@vanguardiasur.com.ar,
        p.zabel@pengutronix.de, gregkh@linuxfoundation.org,
        nicolas.dufresne@collabora.com
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-arm-msm@vger.kernel.org,
        linux-rockchip@lists.infradead.org, linux-staging@lists.linux.dev,
        kernel@collabora.com
References: <20230824092133.39510-1-benjamin.gaignard@collabora.com>
 <20230824092133.39510-3-benjamin.gaignard@collabora.com>
 <397c6779-6153-5df2-a9f7-708bb7fcf58d@xs4all.nl>
 <73e3e87b-78d6-13b2-8a20-09a75d5f23d0@collabora.com>
 <ac1a0848-8b95-0141-c590-f29d74e8c9da@xs4all.nl>
 <07c2de04-f4a7-71e2-ef41-64e87495ff42@collabora.com>
From:   Hans Verkuil <hverkuil-cisco@xs4all.nl>
In-Reply-To: <07c2de04-f4a7-71e2-ef41-64e87495ff42@collabora.com>
Content-Type: text/plain; charset=UTF-8
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Precedence: bulk

On 31/08/2023 09:54, Benjamin Gaignard wrote:
> 
> Le 30/08/2023 à 18:36, Hans Verkuil a écrit :
>> On 30/08/2023 18:24, Benjamin Gaignard wrote:
>>> Le 30/08/2023 à 15:23, Hans Verkuil a écrit :
>>>> On 24/08/2023 11:21, Benjamin Gaignard wrote:
>>>>> The first step before changing how vb2 buffers are stored into queue
>>>>> is to avoid direct access to bufs arrays.
>>>>>
>>>>> This patch adds 2 helpers functions to add and remove vb2 buffers
>>>>> from a queue. With these 2 and vb2_get_buffer(), bufs field of
>>>>> struct vb2_queue becomes like a private member of the structure.
>>>>>
>>>>> After each call to vb2_get_buffer() we need to be sure that we get
>>>>> a valid pointer so check the return value of all of them.
>>>>>
>>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>>>>>
>>>>> # Conflicts:
>>>>> #    drivers/media/common/videobuf2/videobuf2-core.c
>>>>> ---
>>>>>    .../media/common/videobuf2/videobuf2-core.c   | 203 ++++++++++++++----
>>>>>    .../media/common/videobuf2/videobuf2-v4l2.c   |  28 ++-
>>>>>    drivers/media/platform/amphion/vpu_dbg.c      |  22 +-
>>>>>    .../platform/mediatek/jpeg/mtk_jpeg_core.c    |   6 +-
>>>>>    .../vcodec/decoder/vdec/vdec_vp9_req_lat_if.c |   2 +-
>>>>>    drivers/media/platform/st/sti/hva/hva-v4l2.c  |   4 +
>>>>>    drivers/media/test-drivers/visl/visl-dec.c    |  28 ++-
>>>>>    .../staging/media/atomisp/pci/atomisp_ioctl.c |   2 +-
>>>>>    8 files changed, 230 insertions(+), 65 deletions(-)
>>>>>
>>>>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>>>>> index e06905533ef4..8aa13591b782 100644
>>>>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>>>>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>>>>> @@ -403,6 +403,37 @@ static void init_buffer_cache_hints(struct vb2_queue *q, struct vb2_buffer *vb)
>>>>>            vb->skip_cache_sync_on_finish = 1;
>>>>>    }
>>>>>    +/**
>>>>> + * vb2_queue_add_buffer() - add a buffer to a queue
>>>>> + * @q:    pointer to &struct vb2_queue with videobuf2 queue.
>>>>> + * @vb:    pointer to &struct vb2_buffer to be added to the queue.
>>>>> + * @index: index where add vb2_buffer in the queue
>>>>> + */
>>>>> +static bool vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, int index)
>>>>> +{
>>>>> +    if (index < VB2_MAX_FRAME && !q->bufs[index]) {
>>>>> +        q->bufs[index] = vb;
>>>>> +        vb->index = index;
>>>>> +        vb->vb2_queue = q;
>>>>> +        return true;
>>>>> +    }
>>>>> +
>>>>> +    return false;
>>>>> +}
>>>>> +
>>>>> +/**
>>>>> + * vb2_queue_remove_buffer() - remove a buffer from a queue
>>>>> + * @q:    pointer to &struct vb2_queue with videobuf2 queue.
>>>>> + * @vb:    pointer to &struct vb2_buffer to be removed from the queue.
>>>>> + */
>>>>> +static void vb2_queue_remove_buffer(struct vb2_queue *q, struct vb2_buffer *vb)
>>>>> +{
>>>>> +    if (vb->index < VB2_MAX_FRAME) {
>>>>> +        q->bufs[vb->index] = NULL;
>>>>> +        vb->vb2_queue = NULL;
>>>>> +    }
>>>>> +}
>>>>> +
>>>>>    /*
>>>>>     * __vb2_queue_alloc() - allocate vb2 buffer structures and (for MMAP type)
>>>>>     * video buffer memory for all buffers/planes on the queue and initializes the
>>>>> @@ -431,9 +462,7 @@ 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->type = q->type;
>>>>>            vb->memory = memory;
>>>>>            init_buffer_cache_hints(q, vb);
>>>>> @@ -443,7 +472,11 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>>>>>            }
>>>>>            call_void_bufop(q, init_buffer, vb);
>>>>>    -        q->bufs[vb->index] = vb;
>>>>> +        if (!vb2_queue_add_buffer(q, vb, q->num_buffers + buffer)) {
>>>>> +            dprintk(q, 1, "failed adding buffer %d to queue\n", buffer);
>>>>> +            kfree(vb);
>>>>> +            break;
>>>>> +        }
>>>>>              /* Allocate video buffer memory for the MMAP type */
>>>>>            if (memory == VB2_MEMORY_MMAP) {
>>>>> @@ -451,7 +484,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>>>>>                if (ret) {
>>>>>                    dprintk(q, 1, "failed allocating memory for buffer %d\n",
>>>>>                        buffer);
>>>>> -                q->bufs[vb->index] = NULL;
>>>>> +                vb2_queue_remove_buffer(q, vb);
>>>>>                    kfree(vb);
>>>>>                    break;
>>>>>                }
>>>>> @@ -466,7 +499,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>>>>>                    dprintk(q, 1, "buffer %d %p initialization failed\n",
>>>>>                        buffer, vb);
>>>>>                    __vb2_buf_mem_free(vb);
>>>>> -                q->bufs[vb->index] = NULL;
>>>>> +                vb2_queue_remove_buffer(q, vb);
>>>>>                    kfree(vb);
>>>>>                    break;
>>>>>                }
>>>>> @@ -489,7 +522,7 @@ static void __vb2_free_mem(struct vb2_queue *q, unsigned int buffers)
>>>>>          for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
>>>>>             ++buffer) {
>>>>> -        vb = q->bufs[buffer];
>>>>> +        vb = vb2_get_buffer(q, buffer);
>>>>>            if (!vb)
>>>>>                continue;
>>>>>    @@ -517,7 +550,7 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>>>>>        /* Call driver-provided cleanup function for each buffer, if provided */
>>>>>        for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
>>>>>             ++buffer) {
>>>>> -        struct vb2_buffer *vb = q->bufs[buffer];
>>>>> +        struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>>>>>              if (vb && vb->planes[0].mem_priv)
>>>>>                call_void_vb_qop(vb, buf_cleanup, vb);
>>>>> @@ -557,15 +590,20 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>>>>>            q->cnt_unprepare_streaming = 0;
>>>>>        }
>>>>>        for (buffer = 0; buffer < q->num_buffers; ++buffer) {
>>>>> -        struct vb2_buffer *vb = q->bufs[buffer];
>>>>> -        bool unbalanced = vb->cnt_mem_alloc != vb->cnt_mem_put ||
>>>>> -                  vb->cnt_mem_prepare != vb->cnt_mem_finish ||
>>>>> -                  vb->cnt_mem_get_userptr != vb->cnt_mem_put_userptr ||
>>>>> -                  vb->cnt_mem_attach_dmabuf != vb->cnt_mem_detach_dmabuf ||
>>>>> -                  vb->cnt_mem_map_dmabuf != vb->cnt_mem_unmap_dmabuf ||
>>>>> -                  vb->cnt_buf_queue != vb->cnt_buf_done ||
>>>>> -                  vb->cnt_buf_prepare != vb->cnt_buf_finish ||
>>>>> -                  vb->cnt_buf_init != vb->cnt_buf_cleanup;
>>>>> +        struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>>>>> +        bool unbalanced;
>>>>> +
>>>>> +        if (!vb)
>>>>> +            continue;
>>>>> +
>>>>> +        unbalanced = vb->cnt_mem_alloc != vb->cnt_mem_put ||
>>>>> +                 vb->cnt_mem_prepare != vb->cnt_mem_finish ||
>>>>> +                 vb->cnt_mem_get_userptr != vb->cnt_mem_put_userptr ||
>>>>> +                 vb->cnt_mem_attach_dmabuf != vb->cnt_mem_detach_dmabuf ||
>>>>> +                 vb->cnt_mem_map_dmabuf != vb->cnt_mem_unmap_dmabuf ||
>>>>> +                 vb->cnt_buf_queue != vb->cnt_buf_done ||
>>>>> +                 vb->cnt_buf_prepare != vb->cnt_buf_finish ||
>>>>> +                 vb->cnt_buf_init != vb->cnt_buf_cleanup;
>>>>>              if (unbalanced || debug) {
>>>> I think we should drop the '|| debug' part. It is already annoying today to see these
>>>> messages when the debug parameter is > 0, and now the number of buffers is still
>>>> fairly small. But if we allow a lot more buffers, then this will really spam the
>>>> kernel log.
>>>>
>>>> I think this should be dropped, and we only report unbalanced buffers.
>>>>
>>>> And another optimization is to only report the unbalanced counters. Right now
>>>> it reports all counters, but it is again too much spamming of the kernel log.
>>>>
>>>> I think this change can be done as a separate patch before this patch.
>>>> That way it can be picked up separately from the other changes in this series.
>>>>
>>>>>                pr_info("   counters for queue %p, buffer %d:%s\n",
>>>>> @@ -597,8 +635,13 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>>>>>        /* Free vb2 buffers */
>>>>>        for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
>>>>>             ++buffer) {
>>>>> -        kfree(q->bufs[buffer]);
>>>>> -        q->bufs[buffer] = NULL;
>>>>> +        struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>>>>> +
>>>>> +        if (!vb)
>>>>> +            continue;
>>>>> +
>>>>> +        vb2_queue_remove_buffer(q, vb);
>>>>> +        kfree(vb);
>>>>>        }
>>>>>          q->num_buffers -= buffers;
>>>>> @@ -634,7 +677,12 @@ static bool __buffers_in_use(struct vb2_queue *q)
>>>>>    {
>>>>>        unsigned int buffer;
>>>>>        for (buffer = 0; buffer < q->num_buffers; ++buffer) {
>>>>> -        if (vb2_buffer_in_use(q, q->bufs[buffer]))
>>>>> +        struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>>>>> +
>>>>> +        if (!vb)
>>>>> +            continue;
>>>>> +
>>>>> +        if (vb2_buffer_in_use(q, vb))
>>>>>                return true;
>>>>>        }
>>>>>        return false;
>>>>> @@ -642,7 +690,10 @@ static bool __buffers_in_use(struct vb2_queue *q)
>>>>>      void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb)
>>>>>    {
>>>>> -    call_void_bufop(q, fill_user_buffer, q->bufs[index], pb);
>>>>> +    struct vb2_buffer *vb = vb2_get_buffer(q, index);
>>>>> +
>>>>> +    if (vb)
>>>>> +        call_void_bufop(q, fill_user_buffer, vb, pb);
>>>> I think that rather than passing the index (that then has to be verified)
>>>> it is better to pass the vb2_buffer pointer directly and leave it up to
>>>> the caller to do the index verification.
>>>>
>>>> Another option is to drop this function altogether and let the called
>>>> call the fill_user_buffer function. Either works for me.
>>>>
>>>>>    }
>>>>>    EXPORT_SYMBOL_GPL(vb2_core_querybuf);
>>>>>    @@ -1553,7 +1604,13 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
>>>> Here too it is better to pass the vb2_buffer pointer instead of an index.
>>>>
>>>> This function assumes that the index is valid, so the called actually does the
>>>> validation. Passing the vb pointer instead of the index makes more sense
>>>> in this new situation.
>>>>
>>>> This is also true for two other core functions: vb2_core_qbuf and vb2_core_expbuf.
>>>>
>>>>>        struct vb2_buffer *vb;
>>>>>        int ret;
>>>>>    -    vb = q->bufs[index];
>>>>> +    vb = vb2_get_buffer(q, index);
>>>>> +
>>>>> +    if (!vb) {
>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>> +        return -EINVAL;
>>>>> +    }
>>>> Changing that avoids having to add this check, so it simplifies the code.
>>>>
>>>> I think that this change can be done in a separate patch before this one.
>>>>
>>>> It makes sense to apply that regardless of the remainder of this series.
>>>>
>>>>> +
>>>>>        if (vb->state != VB2_BUF_STATE_DEQUEUED) {
>>>>>            dprintk(q, 1, "invalid buffer state %s\n",
>>>>>                vb2_state_name(vb->state));
>>>>> @@ -1624,7 +1681,11 @@ static int vb2_start_streaming(struct vb2_queue *q)
>>>>>             * correctly return them to vb2.
>>>>>             */
>>>>>            for (i = 0; i < q->num_buffers; ++i) {
>>>>> -            vb = q->bufs[i];
>>>>> +            vb = vb2_get_buffer(q, i);
>>>>> +
>>>>> +            if (!vb)
>>>>> +                continue;
>>>>> +
>>>>>                if (vb->state == VB2_BUF_STATE_ACTIVE)
>>>>>                    vb2_buffer_done(vb, VB2_BUF_STATE_QUEUED);
>>>>>            }
>>>>> @@ -1652,7 +1713,12 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
>>>>>            return -EIO;
>>>>>        }
>>>>>    -    vb = q->bufs[index];
>>>>> +    vb = vb2_get_buffer(q, index);
>>>>> +
>>>>> +    if (!vb) {
>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>> +        return -EINVAL;
>>>>> +    }
>>>>>          if (!req && vb->state != VB2_BUF_STATE_IN_REQUEST &&
>>>>>            q->requires_requests) {
>>>>> @@ -2028,12 +2094,18 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
>>>>>         * to vb2 in stop_streaming().
>>>>>         */
>>>>>        if (WARN_ON(atomic_read(&q->owned_by_drv_count))) {
>>>>> -        for (i = 0; i < q->num_buffers; ++i)
>>>>> -            if (q->bufs[i]->state == VB2_BUF_STATE_ACTIVE) {
>>>>> +        for (i = 0; i < q->num_buffers; ++i) {
>>>>> +            struct vb2_buffer *vb = vb2_get_buffer(q, i);
>>>>> +
>>>>> +            if (!vb)
>>>>> +                continue;
>>>>> +
>>>>> +            if (vb->state == VB2_BUF_STATE_ACTIVE) {
>>>>>                    pr_warn("driver bug: stop_streaming operation is leaving buf %p in active state\n",
>>>>> -                    q->bufs[i]);
>>>>> -                vb2_buffer_done(q->bufs[i], VB2_BUF_STATE_ERROR);
>>>>> +                    vb);
>>>>> +                vb2_buffer_done(vb, VB2_BUF_STATE_ERROR);
>>>>>                }
>>>>> +        }
>>>>>            /* Must be zero now */
>>>>>            WARN_ON(atomic_read(&q->owned_by_drv_count));
>>>>>        }
>>>>> @@ -2067,9 +2139,14 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
>>>>>         * be changed, so we can't move the buf_finish() to __vb2_dqbuf().
>>>>>         */
>>>>>        for (i = 0; i < q->num_buffers; ++i) {
>>>>> -        struct vb2_buffer *vb = q->bufs[i];
>>>>> -        struct media_request *req = vb->req_obj.req;
>>>>> +        struct vb2_buffer *vb;
>>>>> +        struct media_request *req;
>>>>> +
>>>>> +        vb = vb2_get_buffer(q, i);
>>>>> +        if (!vb)
>>>>> +            continue;
>>>>>    +        req = vb->req_obj.req;
>>>>>            /*
>>>>>             * If a request is associated with this buffer, then
>>>>>             * call buf_request_cancel() to give the driver to complete()
>>>>> @@ -2219,7 +2296,10 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off,
>>>>>        buffer = (off >> (PLANE_INDEX_SHIFT + PAGE_SHIFT)) & MAX_BUFFERS;
>>>>>        plane = (off >> PAGE_SHIFT) & PLANE_INDEX_MASK;
>>>>>    -    vb = q->bufs[buffer];
>>>>> +    vb = vb2_get_buffer(q, buffer);
>>>>> +    if (!vb)
>>>>> +        return -EINVAL;
>>>>> +
>>>>>        if (vb->planes[plane].m.offset == off) {
>>>>>            *_buffer = buffer;
>>>>>            *_plane = plane;
>>>>> @@ -2262,7 +2342,12 @@ int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
>>>>>            return -EINVAL;
>>>>>        }
>>>>>    -    vb = q->bufs[index];
>>>>> +    vb = vb2_get_buffer(q, index);
>>>>> +
>>>>> +    if (!vb) {
>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>> +        return -EINVAL;
>>>>> +    }
>>>>>          if (plane >= vb->num_planes) {
>>>>>            dprintk(q, 1, "buffer plane out of range\n");
>>>>> @@ -2339,7 +2424,13 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
>>>>>        if (ret)
>>>>>            goto unlock;
>>>>>    -    vb = q->bufs[buffer];
>>>>> +    vb = vb2_get_buffer(q, buffer);
>>>>> +
>>>>> +    if (!vb) {
>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>> +        ret = -EINVAL;
>>>>> +        goto unlock;
>>>>> +    }
>>>>>          /*
>>>>>         * MMAP requires page_aligned buffers.
>>>>> @@ -2396,7 +2487,12 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
>>>>>        if (ret)
>>>>>            goto unlock;
>>>>>    -    vb = q->bufs[buffer];
>>>>> +    vb = vb2_get_buffer(q, buffer);
>>>>> +    if (!vb) {
>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>> +        ret = -EINVAL;
>>>>> +        goto unlock;
>>>>> +    }
>>>>>          vaddr = vb2_plane_vaddr(vb, plane);
>>>>>        mutex_unlock(&q->mmap_lock);
>>>>> @@ -2625,6 +2721,7 @@ struct vb2_fileio_data {
>>>>>    static int __vb2_init_fileio(struct vb2_queue *q, int read)
>>>>>    {
>>>>>        struct vb2_fileio_data *fileio;
>>>>> +    struct vb2_buffer *vb;
>>>>>        int i, ret;
>>>>>        unsigned int count = 0;
>>>>>    @@ -2679,7 +2776,13 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>>>>>         * Check if plane_count is correct
>>>>>         * (multiplane buffers are not supported).
>>>>>         */
>>>>> -    if (q->bufs[0]->num_planes != 1) {
>>>>> +    vb = vb2_get_buffer(q, 0);
>>>>> +    if (!vb) {
>>>>> +        ret = -EBUSY;
>>>>> +        goto err_reqbufs;
>>>>> +    }
>>>> This cannot happen. These fileio helper functions implement the read() support
>>>> and all the buffer allocation happens here. Userspace can never add or delete
>>>> buffers later, so there will never be holes. It is safe to assume that
>>>> vb2_get_buffer(q, i) will always return a valid vb pointer for i in the range
>>>> of 0 - q->num_buffers-1.
>>>>
>>>> Perhaps add a comment to that effect, but otherwise you can drop the checks.
>>>>
>>>>> +
>>>>> +    if (vb->num_planes != 1) {
>>>>>            ret = -EBUSY;
>>>>>            goto err_reqbufs;
>>>>>        }
>>>>> @@ -2688,12 +2791,17 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>>>>>         * Get kernel address of each buffer.
>>>>>         */
>>>>>        for (i = 0; i < q->num_buffers; i++) {
>>>>> -        fileio->bufs[i].vaddr = vb2_plane_vaddr(q->bufs[i], 0);
>>>>> +        vb = vb2_get_buffer(q, i);
>>>>> +
>>>>> +        if (!vb)
>>>>> +            continue;
>>>>> +
>>>>> +        fileio->bufs[i].vaddr = vb2_plane_vaddr(vb, 0);
>>>>>            if (fileio->bufs[i].vaddr == NULL) {
>>>>>                ret = -EINVAL;
>>>>>                goto err_reqbufs;
>>>>>            }
>>>>> -        fileio->bufs[i].size = vb2_plane_size(q->bufs[i], 0);
>>>>> +        fileio->bufs[i].size = vb2_plane_size(vb, 0);
>>>>>        }
>>>>>          /*
>>>>> @@ -2821,15 +2929,18 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
>>>>>              fileio->cur_index = index;
>>>>>            buf = &fileio->bufs[index];
>>>>> -        b = q->bufs[index];
>>>>> +        b = vb2_get_buffer(q, index);
>>>>> +
>>>>> +        if (!b)
>>>>> +            return -EINVAL;
>>>>>              /*
>>>>>             * Get number of bytes filled by the driver
>>>>>             */
>>>>>            buf->pos = 0;
>>>>>            buf->queued = 0;
>>>>> -        buf->size = read ? vb2_get_plane_payload(q->bufs[index], 0)
>>>>> -                 : vb2_plane_size(q->bufs[index], 0);
>>>>> +        buf->size = read ? vb2_get_plane_payload(b, 0)
>>>>> +                 : vb2_plane_size(b, 0);
>>>>>            /* Compensate for data_offset on read in the multiplanar case. */
>>>>>            if (is_multiplanar && read &&
>>>>>                    b->planes[0].data_offset < buf->size) {
>>>>> @@ -2872,8 +2983,12 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
>>>>>         * Queue next buffer if required.
>>>>>         */
>>>>>        if (buf->pos == buf->size || (!read && fileio->write_immediately)) {
>>>>> -        struct vb2_buffer *b = q->bufs[index];
>>>>> +        struct vb2_buffer *b = vb2_get_buffer(q, index);
>>>>>    +        if (!b) {
>>>>> +            dprintk(q, 1, "can't find the requested buffer\n");
>>>>> +            return -EINVAL;
>>>>> +        }
>>>>>            /*
>>>>>             * Check if this is the last buffer to read.
>>>>>             */
>>>>> @@ -2899,7 +3014,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
>>>>>             */
>>>>>            buf->pos = 0;
>>>>>            buf->queued = 1;
>>>>> -        buf->size = vb2_plane_size(q->bufs[index], 0);
>>>>> +        buf->size = vb2_plane_size(b, 0);
>>>>>            fileio->q_count += 1;
>>>>>            /*
>>>>>             * If we are queuing up buffers for the first time, then
>>>>> @@ -2970,7 +3085,9 @@ static int vb2_thread(void *data)
>>>>>             * Call vb2_dqbuf to get buffer back.
>>>>>             */
>>>>>            if (prequeue) {
>>>>> -            vb = q->bufs[index++];
>>>>> +            vb = vb2_get_buffer(q, index++);
>>>>> +            if (!vb)
>>>>> +                continue;
>>>>>                prequeue--;
>>>>>            } else {
>>>>>                call_void_qop(q, wait_finish, q);
>>>>> @@ -2979,7 +3096,7 @@ static int vb2_thread(void *data)
>>>>>                call_void_qop(q, wait_prepare, q);
>>>>>                dprintk(q, 5, "file io: vb2_dqbuf result: %d\n", ret);
>>>>>                if (!ret)
>>>>> -                vb = q->bufs[index];
>>>>> +                vb = vb2_get_buffer(q, index);
>>>>>            }
>>>>>            if (ret || threadio->stop)
>>>>>                break;
>>>>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>>> index c7a54d82a55e..724135d41f7f 100644
>>>>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>>> @@ -383,8 +383,7 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
>>>>>            return -EINVAL;
>>>>>        }
>>>>>    -    if (q->bufs[b->index] == NULL) {
>>>>> -        /* Should never happen */
>>>>> +    if (!vb2_get_buffer(q, b->index)) {
>>>>>            dprintk(q, 1, "%s: buffer is NULL\n", opname);
>>>> How about:
>>>>
>>>>             dprintk(q, 1, "%s: buffer %u was deleted\n", opname, b->index);
>>>>
>>>> although perhaps that change is more appropriate in patch 09/10?
>>>>
>>>> Regardless, once it is possible to delete buffers, then this message should be
>>>> adjusted accordingly.
>>>>
>>>>>            return -EINVAL;
>>>>>        }
>>>>> @@ -394,7 +393,7 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
>>>>>            return -EINVAL;
>>>>>        }
>>>>>    -    vb = q->bufs[b->index];
>>>>> +    vb = vb2_get_buffer(q, b->index);
>>>> This can be moved up to the 'if (!vb2_get_buffer(q, b->index)) {' check above.
>>>> That avoids calling vb2_get_buffer twice.
>>>>
>>>>>        vbuf = to_vb2_v4l2_buffer(vb);
>>>>>        ret = __verify_planes_array(vb, b);
>>>>>        if (ret)
>>>>> @@ -628,11 +627,18 @@ static const struct vb2_buf_ops v4l2_buf_ops = {
>>>>>    struct vb2_buffer *vb2_find_buffer(struct vb2_queue *q, u64 timestamp)
>>>>>    {
>>>>>        unsigned int i;
>>>>> +    struct vb2_buffer *vb2;
>>>>>    -    for (i = 0; i < q->num_buffers; i++)
>>>>> -        if (q->bufs[i]->copied_timestamp &&
>>>>> -            q->bufs[i]->timestamp == timestamp)
>>>>> -            return vb2_get_buffer(q, i);
>>>> Perhaps add a comment here that this loop doesn't scale if there
>>>> is a really large number of buffers and something more efficient
>>>> will have to be found in that case.
>>>>
>>>>> +    for (i = 0; i < q->num_buffers; i++) {
>>>>> +        vb2 = vb2_get_buffer(q, i);
>>>>> +
>>>>> +        if (!vb2)
>>>>> +            continue;
>>>>> +
>>>>> +        if (vb2->copied_timestamp &&
>>>>> +            vb2->timestamp == timestamp)
>>>>> +            return vb2;
>>>>> +    }
>>>>>        return NULL;
>>>>>    }
>>>>>    EXPORT_SYMBOL_GPL(vb2_find_buffer);
>>>>> @@ -664,7 +670,13 @@ int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b)
>>>>>            dprintk(q, 1, "buffer index out of range\n");
>>>>>            return -EINVAL;
>>>>>        }
>>>>> -    vb = q->bufs[b->index];
>>>>> +    vb = vb2_get_buffer(q, b->index);
>>>>> +
>>>>> +    if (!vb) {
>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>> +        return -EINVAL;
>>>>> +    }
>>>>> +
>>>>>        ret = __verify_planes_array(vb, b);
>>>>>        if (!ret)
>>>>>            vb2_core_querybuf(q, b->index, b);
>>>>> diff --git a/drivers/media/platform/amphion/vpu_dbg.c b/drivers/media/platform/amphion/vpu_dbg.c
>>>>> index 982c2c777484..a462d6fe4ea9 100644
>>>>> --- a/drivers/media/platform/amphion/vpu_dbg.c
>>>>> +++ b/drivers/media/platform/amphion/vpu_dbg.c
>>>>> @@ -140,11 +140,18 @@ static int vpu_dbg_instance(struct seq_file *s, void *data)
>>>>>          vq = v4l2_m2m_get_src_vq(inst->fh.m2m_ctx);
>>>>>        for (i = 0; i < vq->num_buffers; i++) {
>>>>> -        struct vb2_buffer *vb = vq->bufs[i];
>>>>> -        struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
>>>>> +        struct vb2_buffer *vb;
>>>>> +        struct vb2_v4l2_buffer *vbuf;
>>>>> +
>>>>> +        vb = vb2_get_buffer(vq, i);
>>>>> +        if (!vb)
>>>>> +            continue;
>>>>>              if (vb->state == VB2_BUF_STATE_DEQUEUED)
>>>>>                continue;
>>>>> +
>>>>> +        vbuf = to_vb2_v4l2_buffer(vb);
>>>>> +
>>>>>            num = scnprintf(str, sizeof(str),
>>>>>                    "output [%2d] state = %10s, %8s\n",
>>>>>                    i, vb2_stat_name[vb->state],
>>>>> @@ -155,11 +162,18 @@ static int vpu_dbg_instance(struct seq_file *s, void *data)
>>>>>          vq = v4l2_m2m_get_dst_vq(inst->fh.m2m_ctx);
>>>>>        for (i = 0; i < vq->num_buffers; i++) {
>>>>> -        struct vb2_buffer *vb = vq->bufs[i];
>>>>> -        struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
>>>>> +        struct vb2_buffer *vb;
>>>>> +        struct vb2_v4l2_buffer *vbuf;
>>>>> +
>>>>> +        vb = vb2_get_buffer(vq, i);
>>>>> +        if (!vb)
>>>>> +            continue;
>>>>>              if (vb->state == VB2_BUF_STATE_DEQUEUED)
>>>>>                continue;
>>>>> +
>>>>> +        vbuf = to_vb2_v4l2_buffer(vb);
>>>>> +
>>>>>            num = scnprintf(str, sizeof(str),
>>>>>                    "capture[%2d] state = %10s, %8s\n",
>>>>>                    i, vb2_stat_name[vb->state],
>>>> This can be a separate patch, right? It doesn't depend on any core changes.
>>>>
>>>> And this can also be applied before this patch.
>>> Hans, I would like to clarify this comment (and the following Ditto).
>>> Are you against use vb2_get_buffer() outside core ?
>>> or testing vb2_get_buffer() result ?
>>> The goal of this patch was to remove all access like vq->bufs[i] and to make
>>> sure that vb buffer are always valid.
>> Sorry for the confusion. I meant that AFAICS each of these driver changes can be
>> done in the separate patch and that those separate patches can be applied before
>> this patch. I.e., they are independent.
>>
>> I always prefer specific driver changes to be done as separate patches rather
>> than one patch modifying a lot of drivers in one go. That is not always possible,
>> of course, but in this case I think it is fine, unless I missed something.
> 
> All changes in the drivers use vb2_get_buffer() which is introduced in this patch
> so I can't do them before.
> If you want I can make a patch per driver but after this patch.

??? vb2_get_buffer() has been defined in include/media/videobuf2-core.h for a long
time (2019 to be precise).

Regards,

	Hans

> 
> Regards,
> Benjamin
> 
>>
>> Regards,
>>
>>     Hans
>>
>>> Regards,
>>> Benjamin
>>>
>>>>> diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
>>>>> index 621038aab116..62910a1b8a98 100644
>>>>> --- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
>>>>> +++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
>>>>> @@ -603,7 +603,11 @@ static int mtk_jpeg_qbuf(struct file *file, void *priv, struct v4l2_buffer *buf)
>>>>>            return -EINVAL;
>>>>>        }
>>>>>    -    vb = vq->bufs[buf->index];
>>>>> +    vb = vb2_get_buffer(vq, buf->index);
>>>>> +    if (!vb) {
>>>>> +        dev_err(ctx->jpeg->dev, "buffer not found\n");
>>>>> +        return -EINVAL;
>>>>> +    }
>>>>>        jpeg_src_buf = mtk_jpeg_vb2_to_srcbuf(vb);
>>>>>        jpeg_src_buf->bs_size = buf->m.planes[0].bytesused;
>>>>>    
>>>> Ditto.
>>>>
>>>>> diff --git a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
>>>>> index e393e3e668f8..3d2ae0e1b5b6 100644
>>>>> --- a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
>>>>> +++ b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
>>>>> @@ -1696,7 +1696,7 @@ static int vdec_vp9_slice_setup_core_buffer(struct vdec_vp9_slice_instance *inst
>>>>>          /* update internal buffer's width/height */
>>>>>        for (i = 0; i < vq->num_buffers; i++) {
>>>>> -        if (vb == vq->bufs[i]) {
>>>>> +        if (vb == vb2_get_buffer(vq, i)) {
>>>>>                instance->dpb[i].width = w;
>>>>>                instance->dpb[i].height = h;
>>>>>                break;
>>>> Ditto.
>>>>
>>>>> diff --git a/drivers/media/platform/st/sti/hva/hva-v4l2.c b/drivers/media/platform/st/sti/hva/hva-v4l2.c
>>>>> index 3a848ca32a0e..326be09bdb55 100644
>>>>> --- a/drivers/media/platform/st/sti/hva/hva-v4l2.c
>>>>> +++ b/drivers/media/platform/st/sti/hva/hva-v4l2.c
>>>>> @@ -577,6 +577,10 @@ static int hva_qbuf(struct file *file, void *priv, struct v4l2_buffer *buf)
>>>>>            }
>>>>>              vb2_buf = vb2_get_buffer(vq, buf->index);
>>>>> +        if (!vb2_buf) {
>>>>> +            dev_dbg(dev, "%s buffer index %d not found\n", ctx->name, buf->index);
>>>>> +            return -EINVAL;
>>>>> +        }
>>>>>            stream = to_hva_stream(to_vb2_v4l2_buffer(vb2_buf));
>>>>>            stream->bytesused = buf->bytesused;
>>>>>        }
>>>> Ditto.
>>>>
>>>>> diff --git a/drivers/media/test-drivers/visl/visl-dec.c b/drivers/media/test-drivers/visl/visl-dec.c
>>>>> index 318d675e5668..ba20ea998d19 100644
>>>>> --- a/drivers/media/test-drivers/visl/visl-dec.c
>>>>> +++ b/drivers/media/test-drivers/visl/visl-dec.c
>>>>> @@ -290,13 +290,20 @@ static void visl_tpg_fill(struct visl_ctx *ctx, struct visl_run *run)
>>>>>        for (i = 0; i < out_q->num_buffers; i++) {
>>>>>            char entry[] = "index: %u, state: %s, request_fd: %d, ";
>>>>>            u32 old_len = len;
>>>>> -        char *q_status = visl_get_vb2_state(out_q->bufs[i]->state);
>>>>> +        struct vb2_buffer *vb2;
>>>>> +        char *q_status;
>>>>> +
>>>>> +        vb2 = vb2_get_buffer(out_q, i);
>>>>> +        if (!vb2)
>>>>> +            continue;
>>>>> +
>>>>> +        q_status = visl_get_vb2_state(vb2->state);
>>>>>              len += scnprintf(&buf[len], TPG_STR_BUF_SZ - len,
>>>>>                     entry, i, q_status,
>>>>> -                 to_vb2_v4l2_buffer(out_q->bufs[i])->request_fd);
>>>>> +                 to_vb2_v4l2_buffer(vb2)->request_fd);
>>>>>    -        len += visl_fill_bytesused(to_vb2_v4l2_buffer(out_q->bufs[i]),
>>>>> +        len += visl_fill_bytesused(to_vb2_v4l2_buffer(vb2),
>>>>>                           &buf[len],
>>>>>                           TPG_STR_BUF_SZ - len);
>>>>>    @@ -342,13 +349,20 @@ static void visl_tpg_fill(struct visl_ctx *ctx, struct visl_run *run)
>>>>>        len = 0;
>>>>>        for (i = 0; i < cap_q->num_buffers; i++) {
>>>>>            u32 old_len = len;
>>>>> -        char *q_status = visl_get_vb2_state(cap_q->bufs[i]->state);
>>>>> +        struct vb2_buffer *vb2;
>>>>> +        char *q_status;
>>>>> +
>>>>> +        vb2 = vb2_get_buffer(cap_q, i);
>>>>> +        if (!vb2)
>>>>> +            continue;
>>>>> +
>>>>> +        q_status = visl_get_vb2_state(vb2->state);
>>>>>              len += scnprintf(&buf[len], TPG_STR_BUF_SZ - len,
>>>>>                     "index: %u, status: %s, timestamp: %llu, is_held: %d",
>>>>> -                 cap_q->bufs[i]->index, q_status,
>>>>> -                 cap_q->bufs[i]->timestamp,
>>>>> -                 to_vb2_v4l2_buffer(cap_q->bufs[i])->is_held);
>>>>> +                 vb2->index, q_status,
>>>>> +                 vb2->timestamp,
>>>>> +                 to_vb2_v4l2_buffer(vb2)->is_held);
>>>>>              tpg_gen_text(&ctx->tpg, basep, line++ * line_height, 16, &buf[old_len]);
>>>>>            frame_dprintk(ctx->dev, run->dst->sequence, "%s", &buf[old_len]);
>>>> Ditto.
>>>>
>>>>> diff --git a/drivers/staging/media/atomisp/pci/atomisp_ioctl.c b/drivers/staging/media/atomisp/pci/atomisp_ioctl.c
>>>>> index d2174156573a..4b65c69fa60d 100644
>>>>> --- a/drivers/staging/media/atomisp/pci/atomisp_ioctl.c
>>>>> +++ b/drivers/staging/media/atomisp/pci/atomisp_ioctl.c
>>>>> @@ -1061,7 +1061,7 @@ static int atomisp_dqbuf_wrapper(struct file *file, void *fh, struct v4l2_buffer
>>>>>        if (ret)
>>>>>            return ret;
>>>>>    -    vb = pipe->vb_queue.bufs[buf->index];
>>>>> +    vb = vb2_get_buffer(&pipe->vb_queue, buf->index);
>>>>>        frame = vb_to_frame(vb);
>>>>>          buf->reserved = asd->frame_status[buf->index];
>>>> Ditto.
>>>>
>>>> Background: I think it is really useful to merge a lot of the groundwork early
>>>> on, where possible. It simplifies the remainder of the patch series.
>>>>
>>>> Regards,
>>>>
>>>>      Hans
>>>>