aboutsummaryrefslogtreecommitdiff
path: root/Documentation/userspace-api/media/v4l/dmabuf.rst
diff options
context:
space:
mode:
authorLibravatar Linus Torvalds <torvalds@linux-foundation.org>2023-02-21 18:24:12 -0800
committerLibravatar Linus Torvalds <torvalds@linux-foundation.org>2023-02-21 18:24:12 -0800
commit5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch)
treecc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/userspace-api/media/v4l/dmabuf.rst
downloadlinux-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/dmabuf.rst')
-rw-r--r--Documentation/userspace-api/media/v4l/dmabuf.rst162
1 files changed, 162 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/dmabuf.rst b/Documentation/userspace-api/media/v4l/dmabuf.rst
new file mode 100644
index 000000000..50fba11c2
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/dmabuf.rst
@@ -0,0 +1,162 @@
+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
+
+.. _dmabuf:
+
+************************************
+Streaming I/O (DMA buffer importing)
+************************************
+
+The DMABUF framework provides a generic method for sharing buffers
+between multiple devices. Device drivers that support DMABUF can export
+a DMA buffer to userspace as a file descriptor (known as the exporter
+role), import a DMA buffer from userspace using a file descriptor
+previously exported for a different or the same device (known as the
+importer role), or both. This section describes the DMABUF importer role
+API in V4L2.
+
+Refer to :ref:`DMABUF exporting <VIDIOC_EXPBUF>` for details about
+exporting V4L2 buffers as DMABUF file descriptors.
+
+Input and output devices support the streaming 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 <VIDIOC_QUERYCAP>` ioctl is set. Whether
+importing DMA buffers through DMABUF file descriptors is supported is
+determined by calling the :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>`
+ioctl with the memory type set to ``V4L2_MEMORY_DMABUF``.
+
+This I/O method is dedicated to sharing DMA buffers between different
+devices, which may be V4L devices or other video-related devices (e.g.
+DRM). Buffers (planes) are allocated by a driver on behalf of an
+application. Next, these buffers are exported to the application as file
+descriptors using an API which is specific for an allocator driver. Only
+such file descriptor are exchanged. The descriptors 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 DMABUF I/O mode by calling the
+:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` with the desired buffer type.
+
+Example: Initiating streaming I/O with DMABUF file descriptors
+==============================================================
+
+.. code-block:: c
+
+ struct v4l2_requestbuffers reqbuf;
+
+ memset(&reqbuf, 0, sizeof (reqbuf));
+ reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+ reqbuf.memory = V4L2_MEMORY_DMABUF;
+ reqbuf.count = 1;
+
+ if (ioctl(fd, VIDIOC_REQBUFS, &reqbuf) == -1) {
+ if (errno == EINVAL)
+ printf("Video capturing or DMABUF streaming is not supported\\n");
+ else
+ perror("VIDIOC_REQBUFS");
+
+ exit(EXIT_FAILURE);
+ }
+
+The buffer (plane) file descriptor is passed on the fly with the
+:ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl. In case of multiplanar
+buffers, every plane can be associated with a different DMABUF
+descriptor. Although buffers are commonly cycled, applications can pass
+a different DMABUF descriptor at each :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` call.
+
+Example: Queueing DMABUF using single plane API
+===============================================
+
+.. code-block:: c
+
+ int buffer_queue(int v4lfd, int index, int dmafd)
+ {
+ struct v4l2_buffer buf;
+
+ memset(&buf, 0, sizeof buf);
+ buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+ buf.memory = V4L2_MEMORY_DMABUF;
+ buf.index = index;
+ buf.m.fd = dmafd;
+
+ if (ioctl(v4lfd, VIDIOC_QBUF, &buf) == -1) {
+ perror("VIDIOC_QBUF");
+ return -1;
+ }
+
+ return 0;
+ }
+
+Example 3.6. Queueing DMABUF using multi plane API
+==================================================
+
+.. code-block:: c
+
+ int buffer_queue_mp(int v4lfd, int index, int dmafd[], int n_planes)
+ {
+ struct v4l2_buffer buf;
+ struct v4l2_plane planes[VIDEO_MAX_PLANES];
+ int i;
+
+ memset(&buf, 0, sizeof buf);
+ buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
+ buf.memory = V4L2_MEMORY_DMABUF;
+ buf.index = index;
+ buf.m.planes = planes;
+ buf.length = n_planes;
+
+ memset(&planes, 0, sizeof planes);
+
+ for (i = 0; i < n_planes; ++i)
+ buf.m.planes[i].m.fd = dmafd[i];
+
+ if (ioctl(v4lfd, VIDIOC_QBUF, &buf) == -1) {
+ perror("VIDIOC_QBUF");
+ return -1;
+ }
+
+ return 0;
+ }
+
+Captured or displayed buffers are dequeued with the
+:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. The driver can unlock the
+buffer 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 <VIDIOC_REQBUFS>`, or when the device is closed.
+
+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
+:c:func:`select()` and :c:func:`poll()`
+functions are always available.
+
+To start and stop capturing or displaying applications call the
+:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` and
+:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` ioctls.
+
+.. 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 DMABUF importing 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,
+and the :c:func:`select()` and :c:func:`poll()`
+functions.