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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/userspace-api/media/mediactl/request-api.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to 'Documentation/userspace-api/media/mediactl/request-api.rst')
-rw-r--r-- | Documentation/userspace-api/media/mediactl/request-api.rst | 253 |
1 files changed, 253 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/mediactl/request-api.rst b/Documentation/userspace-api/media/mediactl/request-api.rst new file mode 100644 index 000000000..6c4cbd9f0 --- /dev/null +++ b/Documentation/userspace-api/media/mediactl/request-api.rst @@ -0,0 +1,253 @@ +.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later +.. c:namespace:: MC + +.. _media-request-api: + +Request API +=========== + +The Request API has been designed to allow V4L2 to deal with requirements of +modern devices (stateless codecs, complex camera pipelines, ...) and APIs +(Android Codec v2). One such requirement is the ability for devices belonging to +the same pipeline to reconfigure and collaborate closely on a per-frame basis. +Another is support of stateless codecs, which require controls to be applied +to specific frames (aka 'per-frame controls') in order to be used efficiently. + +While the initial use-case was V4L2, it can be extended to other subsystems +as well, as long as they use the media controller. + +Supporting these features without the Request API is not always possible and if +it is, it is terribly inefficient: user-space would have to flush all activity +on the media pipeline, reconfigure it for the next frame, queue the buffers to +be processed with that configuration, and wait until they are all available for +dequeuing before considering the next frame. This defeats the purpose of having +buffer queues since in practice only one buffer would be queued at a time. + +The Request API allows a specific configuration of the pipeline (media +controller topology + configuration for each media entity) to be associated with +specific buffers. This allows user-space to schedule several tasks ("requests") +with different configurations in advance, knowing that the configuration will be +applied when needed to get the expected result. Configuration values at the time +of request completion are also available for reading. + +General Usage +------------- + +The Request API extends the Media Controller API and cooperates with +subsystem-specific APIs to support request usage. At the Media Controller +level, requests are allocated from the supporting Media Controller device +node. Their life cycle is then managed through the request file descriptors in +an opaque way. Configuration data, buffer handles and processing results +stored in requests are accessed through subsystem-specific APIs extended for +request support, such as V4L2 APIs that take an explicit ``request_fd`` +parameter. + +Request Allocation +------------------ + +User-space allocates requests using :ref:`MEDIA_IOC_REQUEST_ALLOC` +for the media device node. This returns a file descriptor representing the +request. Typically, several such requests will be allocated. + +Request Preparation +------------------- + +Standard V4L2 ioctls can then receive a request file descriptor to express the +fact that the ioctl is part of said request, and is not to be applied +immediately. See :ref:`MEDIA_IOC_REQUEST_ALLOC` for a list of ioctls that +support this. Configurations set with a ``request_fd`` parameter are stored +instead of being immediately applied, and buffers queued to a request do not +enter the regular buffer queue until the request itself is queued. + +Request Submission +------------------ + +Once the configuration and buffers of the request are specified, it can be +queued by calling :ref:`MEDIA_REQUEST_IOC_QUEUE` on the request file descriptor. +A request must contain at least one buffer, otherwise ``ENOENT`` is returned. +A queued request cannot be modified anymore. + +.. caution:: + For :ref:`memory-to-memory devices <mem2mem>` you can use requests only for + output buffers, not for capture buffers. Attempting to add a capture buffer + to a request will result in an ``EBADR`` error. + +If the request contains configurations for multiple entities, individual drivers +may synchronize so the requested pipeline's topology is applied before the +buffers are processed. Media controller drivers do a best effort implementation +since perfect atomicity may not be possible due to hardware limitations. + +.. caution:: + + It is not allowed to mix queuing requests with directly queuing buffers: + whichever method is used first locks this in place until + :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` is called or the device is + :ref:`closed <func-close>`. Attempts to directly queue a buffer when earlier + a buffer was queued via a request or vice versa will result in an ``EBUSY`` + error. + +Controls can still be set without a request and are applied immediately, +regardless of whether a request is in use or not. + +.. caution:: + + Setting the same control through a request and also directly can lead to + undefined behavior! + +User-space can :c:func:`poll()` a request file descriptor in +order to wait until the request completes. A request is considered complete +once all its associated buffers are available for dequeuing and all the +associated controls have been updated with the values at the time of completion. +Note that user-space does not need to wait for the request to complete to +dequeue its buffers: buffers that are available halfway through a request can +be dequeued independently of the request's state. + +A completed request contains the state of the device after the request was +executed. User-space can query that state by calling +:ref:`ioctl VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` with the request file +descriptor. Calling :ref:`ioctl VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` for a +request that has been queued but not yet completed will return ``EBUSY`` +since the control values might be changed at any time by the driver while the +request is in flight. + +.. _media-request-life-time: + +Recycling and Destruction +------------------------- + +Finally, a completed request can either be discarded or be reused. Calling +:c:func:`close()` on a request file descriptor will make +that file descriptor unusable and the request will be freed once it is no +longer in use by the kernel. That is, if the request is queued and then the +file descriptor is closed, then it won't be freed until the driver completed +the request. + +The :ref:`MEDIA_REQUEST_IOC_REINIT` will clear a request's state and make it +available again. No state is retained by this operation: the request is as +if it had just been allocated. + +Example for a Codec Device +-------------------------- + +For use-cases such as :ref:`codecs <mem2mem>`, the request API can be used +to associate specific controls to +be applied by the driver for the OUTPUT buffer, allowing user-space +to queue many such buffers in advance. It can also take advantage of requests' +ability to capture the state of controls when the request completes to read back +information that may be subject to change. + +Put into code, after obtaining a request, user-space can assign controls and one +OUTPUT buffer to it: + +.. code-block:: c + + struct v4l2_buffer buf; + struct v4l2_ext_controls ctrls; + int req_fd; + ... + if (ioctl(media_fd, MEDIA_IOC_REQUEST_ALLOC, &req_fd)) + return errno; + ... + ctrls.which = V4L2_CTRL_WHICH_REQUEST_VAL; + ctrls.request_fd = req_fd; + if (ioctl(codec_fd, VIDIOC_S_EXT_CTRLS, &ctrls)) + return errno; + ... + buf.type = V4L2_BUF_TYPE_VIDEO_OUTPUT; + buf.flags |= V4L2_BUF_FLAG_REQUEST_FD; + buf.request_fd = req_fd; + if (ioctl(codec_fd, VIDIOC_QBUF, &buf)) + return errno; + +Note that it is not allowed to use the Request API for CAPTURE buffers +since there are no per-frame settings to report there. + +Once the request is fully prepared, it can be queued to the driver: + +.. code-block:: c + + if (ioctl(req_fd, MEDIA_REQUEST_IOC_QUEUE)) + return errno; + +User-space can then either wait for the request to complete by calling poll() on +its file descriptor, or start dequeuing CAPTURE buffers. Most likely, it will +want to get CAPTURE buffers as soon as possible and this can be done using a +regular :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`: + +.. code-block:: c + + struct v4l2_buffer buf; + + memset(&buf, 0, sizeof(buf)); + buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + if (ioctl(codec_fd, VIDIOC_DQBUF, &buf)) + return errno; + +Note that this example assumes for simplicity that for every OUTPUT buffer +there will be one CAPTURE buffer, but this does not have to be the case. + +We can then, after ensuring that the request is completed via polling the +request file descriptor, query control values at the time of its completion via +a call to :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`. +This is particularly useful for volatile controls for which we want to +query values as soon as the capture buffer is produced. + +.. code-block:: c + + struct pollfd pfd = { .events = POLLPRI, .fd = req_fd }; + poll(&pfd, 1, -1); + ... + ctrls.which = V4L2_CTRL_WHICH_REQUEST_VAL; + ctrls.request_fd = req_fd; + if (ioctl(codec_fd, VIDIOC_G_EXT_CTRLS, &ctrls)) + return errno; + +Once we don't need the request anymore, we can either recycle it for reuse with +:ref:`MEDIA_REQUEST_IOC_REINIT`... + +.. code-block:: c + + if (ioctl(req_fd, MEDIA_REQUEST_IOC_REINIT)) + return errno; + +... or close its file descriptor to completely dispose of it. + +.. code-block:: c + + close(req_fd); + +Example for a Simple Capture Device +----------------------------------- + +With a simple capture device, requests can be used to specify controls to apply +for a given CAPTURE buffer. + +.. code-block:: c + + struct v4l2_buffer buf; + struct v4l2_ext_controls ctrls; + int req_fd; + ... + if (ioctl(media_fd, MEDIA_IOC_REQUEST_ALLOC, &req_fd)) + return errno; + ... + ctrls.which = V4L2_CTRL_WHICH_REQUEST_VAL; + ctrls.request_fd = req_fd; + if (ioctl(camera_fd, VIDIOC_S_EXT_CTRLS, &ctrls)) + return errno; + ... + buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + buf.flags |= V4L2_BUF_FLAG_REQUEST_FD; + buf.request_fd = req_fd; + if (ioctl(camera_fd, VIDIOC_QBUF, &buf)) + return errno; + +Once the request is fully prepared, it can be queued to the driver: + +.. code-block:: c + + if (ioctl(req_fd, MEDIA_REQUEST_IOC_QUEUE)) + return errno; + +User-space can then dequeue buffers, wait for the request completion, query +controls and recycle the request as in the M2M example above. |