diff options
author | 2023-02-21 18:24:12 -0800 | |
---|---|---|
committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/userspace-api/media/v4l/userp.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/v4l/userp.rst')
-rw-r--r-- | Documentation/userspace-api/media/v4l/userp.rst | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/userp.rst b/Documentation/userspace-api/media/v4l/userp.rst new file mode 100644 index 000000000..db224f9b6 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/userp.rst @@ -0,0 +1,122 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _userp: + +***************************** +Streaming I/O (User Pointers) +***************************** + +Input and output devices support this I/O method when the +``V4L2_CAP_STREAMING`` flag in the ``capabilities`` field of struct +:c:type:`v4l2_capability` returned by the +:ref:`VIDIOC_QUERYCAP` ioctl is set. If the +particular user pointer method (not only memory mapping) is supported +must be determined by calling the :ref:`VIDIOC_REQBUFS` ioctl +with the memory type set to ``V4L2_MEMORY_USERPTR``. + +This I/O method combines advantages of the read/write and memory mapping +methods. Buffers (planes) are allocated by the application itself, and +can reside for example in virtual or shared memory. Only pointers to +data are exchanged, these pointers and meta-information are passed in +struct :c:type:`v4l2_buffer` (or in struct +:c:type:`v4l2_plane` in the multi-planar API case). The +driver must be switched into user pointer I/O mode by calling the +:ref:`VIDIOC_REQBUFS` with the desired buffer type. +No buffers (planes) are allocated beforehand, consequently they are not +indexed and cannot be queried like mapped buffers with the +:ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>` ioctl. + +Example: Initiating streaming I/O with user pointers +==================================================== + +.. code-block:: c + + struct v4l2_requestbuffers reqbuf; + + memset (&reqbuf, 0, sizeof (reqbuf)); + reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + reqbuf.memory = V4L2_MEMORY_USERPTR; + + if (ioctl (fd, VIDIOC_REQBUFS, &reqbuf) == -1) { + if (errno == EINVAL) + printf ("Video capturing or user pointer streaming is not supported\\n"); + else + perror ("VIDIOC_REQBUFS"); + + exit (EXIT_FAILURE); + } + +Buffer (plane) addresses and sizes are passed on the fly with the +:ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl. Although buffers are commonly +cycled, applications can pass different addresses and sizes at each +:ref:`VIDIOC_QBUF <VIDIOC_QBUF>` call. If required by the hardware the +driver swaps memory pages within physical memory to create a continuous +area of memory. This happens transparently to the application in the +virtual memory subsystem of the kernel. When buffer pages have been +swapped out to disk they are brought back and finally locked in physical +memory for DMA. [#f1]_ + +Filled or displayed buffers are dequeued with the +:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. The driver can unlock the +memory pages at any time between the completion of the DMA and this +ioctl. The memory is also unlocked when +:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` is called, +:ref:`VIDIOC_REQBUFS`, or when the device is closed. +Applications must take care not to free buffers without dequeuing. +Firstly, the buffers remain locked for longer, wasting physical memory. +Secondly the driver will not be notified when the memory is returned to +the application's free list and subsequently reused for other purposes, +possibly completing the requested DMA and overwriting valuable data. + +For capturing applications it is customary to enqueue a number of empty +buffers, to start capturing and enter the read loop. Here the +application waits until a filled buffer can be dequeued, and re-enqueues +the buffer when the data is no longer needed. Output applications fill +and enqueue buffers, when enough buffers are stacked up output is +started. In the write loop, when the application runs out of free +buffers it must wait until an empty buffer can be dequeued and reused. +Two methods exist to suspend execution of the application until one or +more buffers can be dequeued. By default :ref:`VIDIOC_DQBUF +<VIDIOC_QBUF>` blocks when no buffer is in the outgoing queue. When the +``O_NONBLOCK`` flag was given to the :c:func:`open()` function, +:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` returns immediately with an ``EAGAIN`` +error code when no buffer is available. The :ref:`select() +<func-select>` or :c:func:`poll()` function are always +available. + +To start and stop capturing or output applications call the +:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` and +:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` ioctl. + +.. note:: + + :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` removes all buffers from + both queues and unlocks all buffers as a side effect. Since there is no + notion of doing anything "now" on a multitasking system, if an + application needs to synchronize with another event it should examine + the struct :c:type:`v4l2_buffer` ``timestamp`` of captured or + outputted buffers. + +Drivers implementing user pointer I/O must support the +:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>`, :ref:`VIDIOC_QBUF <VIDIOC_QBUF>`, +:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`, :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` +and :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` ioctls, the +:c:func:`select()` and :c:func:`poll()` function. [#f2]_ + +.. [#f1] + We expect that frequently used buffers are typically not swapped out. + Anyway, the process of swapping, locking or generating scatter-gather + lists may be time consuming. The delay can be masked by the depth of + the incoming buffer queue, and perhaps by maintaining caches assuming + a buffer will be soon enqueued again. On the other hand, to optimize + memory usage drivers can limit the number of buffers locked in + advance and recycle the most recently used buffers first. Of course, + the pages of empty buffers in the incoming queue need not be saved to + disk. Output buffers must be saved on the incoming and outgoing queue + because an application may share them with other processes. + +.. [#f2] + At the driver level :c:func:`select()` and :c:func:`poll()` are + the same, and :c:func:`select()` is too important to be optional. + The rest should be evident. |