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Wed, 24 Jan 2024 15:35:33 +0000 (UTC) Message-ID: <81d8f73a-9a9c-445d-a6f5-e1358bf945a6@collabora.com> Date: Wed, 24 Jan 2024 16:35:33 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v17 6/8] media: v4l2: Add DELETE_BUFS ioctl Content-Language: en-US To: Hans Verkuil , mchehab@kernel.org Cc: linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, kernel@collabora.com References: <20240119094944.26763-1-benjamin.gaignard@collabora.com> <20240119094944.26763-7-benjamin.gaignard@collabora.com> <8a19487d-e903-4961-b56b-42079c9362b3@xs4all.nl> From: Benjamin Gaignard In-Reply-To: <8a19487d-e903-4961-b56b-42079c9362b3@xs4all.nl> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 24/01/2024 à 13:33, Hans Verkuil a écrit : > On 19/01/2024 10:49, Benjamin Gaignard wrote: >> VIDIOC_DELETE_BUFS ioctl allows to delete buffers from a queue. >> The number of buffers to delete in given by count field of >> struct v4l2_delete_buffers and the range start at the index >> specified in the same structure. >> >> Signed-off-by: Benjamin Gaignard >> --- >> version 17: >> - rework DELETE_BUFS documentation >> >> .../userspace-api/media/v4l/user-func.rst | 1 + >> .../media/v4l/vidioc-delete-bufs.rst | 80 +++++++++++++++++++ >> .../media/v4l/vidioc-reqbufs.rst | 1 + >> .../media/common/videobuf2/videobuf2-core.c | 42 ++++++++++ >> .../media/common/videobuf2/videobuf2-v4l2.c | 20 +++++ >> drivers/media/v4l2-core/v4l2-dev.c | 1 + >> drivers/media/v4l2-core/v4l2-ioctl.c | 20 +++++ >> include/media/v4l2-ioctl.h | 4 + >> include/media/videobuf2-core.h | 12 +++ >> include/media/videobuf2-v4l2.h | 13 +++ >> include/uapi/linux/videodev2.h | 17 ++++ >> 11 files changed, 211 insertions(+) >> create mode 100644 Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst >> >> diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst >> index 15ff0bf7bbe6..3fd567695477 100644 >> --- a/Documentation/userspace-api/media/v4l/user-func.rst >> +++ b/Documentation/userspace-api/media/v4l/user-func.rst >> @@ -17,6 +17,7 @@ Function Reference >> vidioc-dbg-g-chip-info >> vidioc-dbg-g-register >> vidioc-decoder-cmd >> + vidioc-delete-bufs >> vidioc-dqevent >> vidioc-dv-timings-cap >> vidioc-encoder-cmd >> diff --git a/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst >> new file mode 100644 >> index 000000000000..d409063ceb3f >> --- /dev/null >> +++ b/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst >> @@ -0,0 +1,80 @@ >> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later >> +.. c:namespace:: V4L >> + >> +.. _VIDIOC_DELETE_BUFS: >> + >> +************************ >> +ioctl VIDIOC_DELETE_BUFS >> +************************ >> + >> +Name >> +==== >> + >> +VIDIOC_DELETE_BUFS - Deletes buffers from a queue >> + >> +Synopsis >> +======== >> + >> +.. c:macro:: VIDIOC_DELETE_BUFs >> + >> +``int ioctl(int fd, VIDIOC_DELETE_BUFs, struct v4l2_delete_buffers *argp)`` >> + >> +Arguments >> +========= >> + >> +``fd`` >> + File descriptor returned by :c:func:`open()`. >> + >> +``argp`` >> + Pointer to struct :c:type:`v4l2_delete_buffers`. >> + >> +Description >> +=========== >> + >> +Applications can optionally call the :ref:`VIDIOC_DELETE_BUFS` ioctl to >> +delete buffers from a queue. >> +This ioctl is available if the ``V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS`` capability >> +is set on the queue when :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS` >> +are invoked. >> + >> +.. c:type:: v4l2_delete_buffers >> + >> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| >> + >> +.. flat-table:: struct v4l2_delete_buffers >> + :header-rows: 0 >> + :stub-columns: 0 >> + :widths: 1 1 2 >> + >> + * - __u32 >> + - ``index`` >> + - The starting buffer index to delete. >> + * - __u32 >> + - ``count`` >> + - The number of buffers to be deleted with indices 'index' until 'index + count - 1'. >> + All buffers in this range must be valid and in DEQUEUED state. >> + If count is set to 0 :ref:`VIDIOC_DELETE_BUFS` will do nothing and return 0. >> + * - __u32 >> + - ``type`` >> + - Type of the stream or buffers, this is the same as the struct >> + :c:type:`v4l2_format` ``type`` field. See >> + :c:type:`v4l2_buf_type` for valid values. >> + * - __u32 >> + - ``reserved``\ [13] >> + - A place holder for future extensions. Drivers and applications >> + must set the array to zero. >> + >> +Return Value >> +============ >> + >> +On success 0 is returned, on error -1 and the ``errno`` variable is set >> +appropriately. The generic error codes are described at the >> +:ref:`Generic Error Codes ` chapter. >> + >> +EBUSY >> + File I/O is in progress. >> + Any buffer in range ``index`` to ``index + count - 1`` is not in >> + DEQUEUED state. >> + >> +EINVAL >> + Any buffer in range ``index`` to ``index + count - 1`` doesn't exist in the queue. >> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst >> index 0b3a41a45d05..14d4a49c2945 100644 >> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst >> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst >> @@ -121,6 +121,7 @@ aborting or finishing any DMA in progress, an implicit >> .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF: >> .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS: >> .. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS: >> +.. _V4L2-BUF-CAP-SUPPORTS-DELETE-BUFS: >> >> .. raw:: latex >> >> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c >> index 010505ed92e8..99e631233a54 100644 >> --- a/drivers/media/common/videobuf2/videobuf2-core.c >> +++ b/drivers/media/common/videobuf2/videobuf2-core.c >> @@ -1688,6 +1688,48 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb) >> } >> EXPORT_SYMBOL_GPL(vb2_core_prepare_buf); >> >> +int vb2_core_delete_bufs(struct vb2_queue *q, unsigned int start, unsigned int count) >> +{ >> + unsigned int i, ret = 0; >> + unsigned int q_num_bufs = vb2_get_num_buffers(q); >> + >> + if (count == 0) >> + return 0; >> + >> + if (count > q_num_bufs) >> + return -EINVAL; >> + >> + if (start + count > q->max_num_buffers) > Change this to: > > if (start > q->max_num_buffers - count) > > This avoids the corner case where 'start + count' overflows the unsigned int. > >> + return -EINVAL; >> + >> + /* If streaming keep at least min_queued_buffers + 1 buffers */ >> + if (q->streaming && (q_num_bufs - count < q->min_queued_buffers + 1)) >> + return -EINVAL; > I would drop this. This will be caught automatically by the next check > since if a driver needs q->min_queued_buffers to start the DMA, then > once the DMA stated there will always be that amount of buffers in a > non-DEQUEUED state. > >> + >> + mutex_lock(&q->mmap_lock); >> + >> + /* Check that all buffers in the range exist */ >> + for (i = start; i < start + count; i++) { >> + struct vb2_buffer *vb = vb2_get_buffer(q, i); >> + >> + if (!vb) { >> + ret = -EINVAL; >> + goto unlock; >> + } >> + if (vb->state != VB2_BUF_STATE_DEQUEUED) { >> + ret = -EBUSY; >> + goto unlock; >> + } >> + } >> + __vb2_queue_free(q, start, count); >> + dprintk(q, 2, "%u buffers deleted\n", count); >> + >> +unlock: >> + mutex_unlock(&q->mmap_lock); >> + return ret; >> +} >> +EXPORT_SYMBOL_GPL(vb2_core_delete_bufs); > There is one specific corner case here that needs attention: if ALL buffers > are deleted (something that is possible if STREAMON was called, but no > buffers are queued), then vb2_is_busy will suddenly return false. > > This can have all sorts of subtle consequences since it is now possible > to, for example, change the format. > > There are two options here: > > 1) vb2_is_busy() shouldn't check if there are buffers allocated, instead it > should check if buffers were allocated at least once. So calling REQBUFS > or CREATE_BUFS for the first time will set a flag to 1, until you call > REQBUFS with count 0, or close the filehandle. Deleting all buffers with > DELETE_BUFS will not change that. I will go for this option and add a patch at the beginning of the series. > > 2) We treat deleting all buffers with DELETE_BUFS the same as calling REQBUFS(0), > in which case the code above needs to change. > > I lean towards option 1. My reasoning is that REQBUFS does an implicit STREAMOFF, > and DELETE_BUFS does not and I do not think DELETE_BUFS should allow vb2_is_busy() > to become false. It would still be nice if it can delete all buffers, but we > would have to check if there are no other places where the number of allocated > buffers is checked, when perhaps it really should use vb2_is_busy() instead. > >> + >> /* >> * vb2_start_streaming() - Attempt to start streaming. >> * @q: videobuf2 queue >> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c >> index 03e8080a68a8..626b5283dfdb 100644 >> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c >> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c >> @@ -698,6 +698,8 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory, >> *caps |= V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS; >> if (q->supports_requests) >> *caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS; >> + if (q->supports_delete_bufs) >> + *caps |= V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS; >> if (max_num_bufs) { >> *max_num_bufs = q->max_num_buffers; >> *caps |= V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS; >> @@ -743,6 +745,12 @@ int vb2_prepare_buf(struct vb2_queue *q, struct media_device *mdev, >> } >> EXPORT_SYMBOL_GPL(vb2_prepare_buf); >> >> +int vb2_delete_bufs(struct vb2_queue *q, struct v4l2_delete_buffers *d) >> +{ >> + return vb2_core_delete_bufs(q, d->index, d->count); >> +} >> +EXPORT_SYMBOL_GPL(vb2_delete_bufs); >> + > I would not add this. Drivers that want to support this should implement > vb2_ioctl_delete_bufs(). Eventually I want to get away from these non-vb2_ioctl_ > functions. I need it for v4l2_m2m_ioctl_delete_bufs() implementation because the targeted queue depends of the context. Regards, Benjamin > >> int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create) >> { >> unsigned requested_planes = 1; >> @@ -1001,6 +1009,18 @@ EXPORT_SYMBOL_GPL(vb2_poll); >> >> /* vb2 ioctl helpers */ >> >> +int vb2_ioctl_delete_bufs(struct file *file, void *priv, >> + struct v4l2_delete_buffers *p) >> +{ >> + struct video_device *vdev = video_devdata(file); >> + >> + if (vb2_queue_is_busy(vdev->queue, file)) >> + return -EBUSY; >> + >> + return vb2_delete_bufs(vdev->queue, p); >> +} >> +EXPORT_SYMBOL_GPL(vb2_ioctl_delete_bufs); >> + >> int vb2_ioctl_reqbufs(struct file *file, void *priv, >> struct v4l2_requestbuffers *p) >> { >> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c >> index d13954bd31fd..e764af2e29ff 100644 >> --- a/drivers/media/v4l2-core/v4l2-dev.c >> +++ b/drivers/media/v4l2-core/v4l2-dev.c >> @@ -722,6 +722,7 @@ static void determine_valid_ioctls(struct video_device *vdev) >> SET_VALID_IOCTL(ops, VIDIOC_PREPARE_BUF, vidioc_prepare_buf); >> SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon); >> SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff); >> + SET_VALID_IOCTL(ops, VIDIOC_DELETE_BUFS, vidioc_delete_bufs); >> } >> >> if (is_vid || is_vbi || is_meta) { >> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c >> index 33076af4dfdb..9676cd758426 100644 >> --- a/drivers/media/v4l2-core/v4l2-ioctl.c >> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c >> @@ -489,6 +489,14 @@ static void v4l_print_create_buffers(const void *arg, bool write_only) >> v4l_print_format(&p->format, write_only); >> } >> >> +static void v4l_print_delete_buffers(const void *arg, bool write_only) >> +{ >> + const struct v4l2_delete_buffers *p = arg; >> + >> + pr_cont("type=%s, index=%u, count=%u\n", >> + prt_names(p->type, v4l2_type_names), p->index, p->count); >> +} >> + >> static void v4l_print_streamparm(const void *arg, bool write_only) >> { >> const struct v4l2_streamparm *p = arg; >> @@ -2161,6 +2169,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops, >> return ret ? ret : ops->vidioc_prepare_buf(file, fh, b); >> } >> >> +static int v4l_delete_bufs(const struct v4l2_ioctl_ops *ops, >> + struct file *file, void *fh, void *arg) >> +{ >> + struct v4l2_delete_buffers *delete = arg; >> + int ret = check_fmt(file, delete->type); >> + >> + memset_after(delete, 0, type); > I don't think this is needed since you use INFO_FL_CLEAR() below. That does it for you. > >> + >> + return ret ? ret : ops->vidioc_delete_bufs(file, fh, delete); >> +} >> + >> static int v4l_g_parm(const struct v4l2_ioctl_ops *ops, >> struct file *file, void *fh, void *arg) >> { >> @@ -2910,6 +2929,7 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = { >> IOCTL_INFO(VIDIOC_ENUM_FREQ_BANDS, v4l_enum_freq_bands, v4l_print_freq_band, 0), >> IOCTL_INFO(VIDIOC_DBG_G_CHIP_INFO, v4l_dbg_g_chip_info, v4l_print_dbg_chip_info, INFO_FL_CLEAR(v4l2_dbg_chip_info, match)), >> IOCTL_INFO(VIDIOC_QUERY_EXT_CTRL, v4l_query_ext_ctrl, v4l_print_query_ext_ctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_query_ext_ctrl, id)), >> + IOCTL_INFO(VIDIOC_DELETE_BUFS, v4l_delete_bufs, v4l_print_delete_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_delete_buffers, type)), >> }; >> #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls) >> >> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h >> index edb733f21604..55afbde54211 100644 >> --- a/include/media/v4l2-ioctl.h >> +++ b/include/media/v4l2-ioctl.h >> @@ -163,6 +163,8 @@ struct v4l2_fh; >> * :ref:`VIDIOC_CREATE_BUFS ` ioctl >> * @vidioc_prepare_buf: pointer to the function that implements >> * :ref:`VIDIOC_PREPARE_BUF ` ioctl >> + * @vidioc_delete_bufs: pointer to the function that implements >> + * :ref:`VIDIOC_DELETE_BUFS ` ioctl >> * @vidioc_overlay: pointer to the function that implements >> * :ref:`VIDIOC_OVERLAY ` ioctl >> * @vidioc_g_fbuf: pointer to the function that implements >> @@ -422,6 +424,8 @@ struct v4l2_ioctl_ops { >> struct v4l2_create_buffers *b); >> int (*vidioc_prepare_buf)(struct file *file, void *fh, >> struct v4l2_buffer *b); >> + int (*vidioc_delete_bufs)(struct file *file, void *fh, >> + struct v4l2_delete_buffers *d); >> >> int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i); >> int (*vidioc_g_fbuf)(struct file *file, void *fh, >> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h >> index 8647eee348bd..4e62b31561d9 100644 >> --- a/include/media/videobuf2-core.h >> +++ b/include/media/videobuf2-core.h >> @@ -507,6 +507,7 @@ struct vb2_buf_ops { >> * @supports_requests: this queue supports the Request API. >> * @requires_requests: this queue requires the Request API. If this is set to 1, >> * then supports_requests must be set to 1 as well. >> + * @supports_delete_bufs: this queue supports DELETE_BUFS ioctl. >> * @uses_qbuf: qbuf was used directly for this queue. Set to 1 the first >> * time this is called. Set to 0 when the queue is canceled. >> * If this is 1, then you cannot queue buffers from a request. >> @@ -613,6 +614,7 @@ struct vb2_queue { >> unsigned int quirk_poll_must_check_waiting_for_buffers:1; >> unsigned int supports_requests:1; >> unsigned int requires_requests:1; >> + unsigned int supports_delete_bufs:1; > I am not convinced we want do enable this per-queue. i will have > to think some more about this. > >> unsigned int uses_qbuf:1; >> unsigned int uses_requests:1; >> unsigned int allow_cache_hints:1; >> @@ -865,6 +867,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory, >> */ >> int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb); >> >> +/** >> + * vb2_core_delete_bufs() - >> + * @q: pointer to &struct vb2_queue with videobuf2 queue. >> + * @start: first index of the range of buffers to delete. >> + * @count: number of buffers to delete. >> + * >> + * Return: returns zero on success; an error code otherwise. >> + */ >> +int vb2_core_delete_bufs(struct vb2_queue *q, unsigned int start, unsigned int count); >> + >> /** >> * vb2_core_qbuf() - Queue a buffer from userspace >> * >> diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h >> index 5a845887850b..79cea8459f52 100644 >> --- a/include/media/videobuf2-v4l2.h >> +++ b/include/media/videobuf2-v4l2.h >> @@ -118,6 +118,17 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create); >> */ >> int vb2_prepare_buf(struct vb2_queue *q, struct media_device *mdev, >> struct v4l2_buffer *b); >> +/** >> + * vb2_delete_bufs() - Delete buffers from the queue >> + * >> + * @q: pointer to &struct vb2_queue with videobuf2 queue. >> + * @d: delete parameter, passed from userspace to >> + * &v4l2_ioctl_ops->vidioc_delete_bufs handler in driver >> + * >> + * The return values from this function are intended to be directly returned >> + * from &v4l2_ioctl_ops->vidioc_delete_bufs handler in driver. >> + */ >> +int vb2_delete_bufs(struct vb2_queue *q, struct v4l2_delete_buffers *d); > Drop this. > >> >> /** >> * vb2_qbuf() - Queue a buffer from userspace >> @@ -334,6 +345,8 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i); >> int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i); >> int vb2_ioctl_expbuf(struct file *file, void *priv, >> struct v4l2_exportbuffer *p); >> +int vb2_ioctl_delete_bufs(struct file *file, void *priv, >> + struct v4l2_delete_buffers *p); >> >> /* struct v4l2_file_operations helpers */ >> >> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h >> index 68e7ac178cc2..ce436f924782 100644 >> --- a/include/uapi/linux/videodev2.h >> +++ b/include/uapi/linux/videodev2.h >> @@ -1036,6 +1036,7 @@ struct v4l2_requestbuffers { >> #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF (1 << 5) >> #define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS (1 << 6) >> #define V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS (1 << 7) >> +#define V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS (1 << 8) >> >> /** >> * struct v4l2_plane - plane info for multi-planar buffers >> @@ -2624,6 +2625,20 @@ struct v4l2_create_buffers { >> __u32 reserved[5]; >> }; >> >> +/** >> + * struct v4l2_delete_buffers - VIDIOC_DELETE_BUFS argument >> + * @index: the first buffer to be deleted >> + * @count: number of buffers to delete >> + * @type: enum v4l2_buf_type >> + * @reserved: future extensions >> + */ >> +struct v4l2_delete_buffers { >> + __u32 index; >> + __u32 count; >> + __u32 type; >> + __u32 reserved[13]; >> +}; >> + >> /* >> * I O C T L C O D E S F O R V I D E O D E V I C E S >> * >> @@ -2723,6 +2738,8 @@ struct v4l2_create_buffers { >> #define VIDIOC_DBG_G_CHIP_INFO _IOWR('V', 102, struct v4l2_dbg_chip_info) >> >> #define VIDIOC_QUERY_EXT_CTRL _IOWR('V', 103, struct v4l2_query_ext_ctrl) >> +#define VIDIOC_DELETE_BUFS _IOWR('V', 104, struct v4l2_delete_buffers) >> + >> >> /* Reminder: when adding new ioctls please add support for them to >> drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */ > Regards, > > Hans >