From 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 21 Feb 2023 18:24:12 -0800 Subject: Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 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(). ... --- .../userspace-api/media/v4l/vidioc-g-ext-ctrls.rst | 503 +++++++++++++++++++++ 1 file changed, 503 insertions(+) create mode 100644 Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst (limited to 'Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst') diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst new file mode 100644 index 000000000..892cfeb8b --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst @@ -0,0 +1,503 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_G_EXT_CTRLS: + +****************************************************************** +ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS +****************************************************************** + +Name +==== + +VIDIOC_G_EXT_CTRLS - VIDIOC_S_EXT_CTRLS - VIDIOC_TRY_EXT_CTRLS - Get or set the value of several controls, try control values + +Synopsis +======== + +.. c:macro:: VIDIOC_G_EXT_CTRLS + +``int ioctl(int fd, VIDIOC_G_EXT_CTRLS, struct v4l2_ext_controls *argp)`` + +.. c:macro:: VIDIOC_S_EXT_CTRLS + +``int ioctl(int fd, VIDIOC_S_EXT_CTRLS, struct v4l2_ext_controls *argp)`` + +.. c:macro:: VIDIOC_TRY_EXT_CTRLS + +``int ioctl(int fd, VIDIOC_TRY_EXT_CTRLS, struct v4l2_ext_controls *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_ext_controls`. + +Description +=========== + +These ioctls allow the caller to get or set multiple controls +atomically. Control IDs are grouped into control classes (see +:ref:`ctrl-class`) and all controls in the control array must belong +to the same control class. + +Applications must always fill in the ``count``, ``which``, ``controls`` +and ``reserved`` fields of struct +:c:type:`v4l2_ext_controls`, and initialize the +struct :c:type:`v4l2_ext_control` array pointed to +by the ``controls`` fields. + +To get the current value of a set of controls applications initialize +the ``id``, ``size`` and ``reserved2`` fields of each struct +:c:type:`v4l2_ext_control` and call the +:ref:`VIDIOC_G_EXT_CTRLS ` ioctl. String controls must also set the +``string`` field. Controls of compound types +(``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set) must set the ``ptr`` field. + +If the ``size`` is too small to receive the control result (only +relevant for pointer-type controls like strings), then the driver will +set ``size`` to a valid value and return an ``ENOSPC`` error code. You +should re-allocate the memory to this new size and try again. For the +string type it is possible that the same issue occurs again if the +string has grown in the meantime. It is recommended to call +:ref:`VIDIOC_QUERYCTRL` first and use +``maximum``\ +1 as the new ``size`` value. It is guaranteed that that is +sufficient memory. + +N-dimensional arrays are set and retrieved row-by-row. You cannot set a +partial array, all elements have to be set or retrieved. The total size +is calculated as ``elems`` * ``elem_size``. These values can be obtained +by calling :ref:`VIDIOC_QUERY_EXT_CTRL `. + +To change the value of a set of controls applications initialize the +``id``, ``size``, ``reserved2`` and ``value/value64/string/ptr`` fields +of each struct :c:type:`v4l2_ext_control` and call +the :ref:`VIDIOC_S_EXT_CTRLS ` ioctl. The controls will only be set if *all* +control values are valid. + +To check if a set of controls have correct values applications +initialize the ``id``, ``size``, ``reserved2`` and +``value/value64/string/ptr`` fields of each struct +:c:type:`v4l2_ext_control` and call the +:ref:`VIDIOC_TRY_EXT_CTRLS ` ioctl. It is up to the driver whether wrong +values are automatically adjusted to a valid value or if an error is +returned. + +When the ``id`` or ``which`` is invalid drivers return an ``EINVAL`` error +code. When the value is out of bounds drivers can choose to take the +closest valid value or return an ``ERANGE`` error code, whatever seems more +appropriate. In the first case the new value is set in struct +:c:type:`v4l2_ext_control`. If the new control value +is inappropriate (e.g. the given menu index is not supported by the menu +control), then this will also result in an ``EINVAL`` error code error. + +If ``request_fd`` is set to a not-yet-queued :ref:`request ` +file descriptor and ``which`` is set to ``V4L2_CTRL_WHICH_REQUEST_VAL``, +then the controls are not applied immediately when calling +:ref:`VIDIOC_S_EXT_CTRLS `, but instead are applied by +the driver for the buffer associated with the same request. +If the device does not support requests, then ``EACCES`` will be returned. +If requests are supported but an invalid request file descriptor is given, +then ``EINVAL`` will be returned. + +An attempt to call :ref:`VIDIOC_S_EXT_CTRLS ` for a +request that has already been queued will result in an ``EBUSY`` error. + +If ``request_fd`` is specified and ``which`` is set to +``V4L2_CTRL_WHICH_REQUEST_VAL`` during a call to +:ref:`VIDIOC_G_EXT_CTRLS `, then it will return the +values of the controls at the time of request completion. +If the request is not yet completed, then this will result in an +``EACCES`` error. + +The driver will only set/get these controls if all control values are +correct. This prevents the situation where only some of the controls +were set/get. Only low-level errors (e. g. a failed i2c command) can +still cause this situation. + +.. tabularcolumns:: |p{6.8cm}|p{4.0cm}|p{6.5cm}| + +.. c:type:: v4l2_ext_control + +.. raw:: latex + + \footnotesize + +.. cssclass:: longtable + +.. flat-table:: struct v4l2_ext_control + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - __u32 + - ``id`` + - Identifies the control, set by the application. + * - __u32 + - ``size`` + - The total size in bytes of the payload of this control. + * - :cspan:`2` The ``size`` field is normally 0, but for pointer + controls this should be set to the size of the memory that contains + the payload or that will receive the payload. + If :ref:`VIDIOC_G_EXT_CTRLS ` finds that this value + is less than is required to store the payload result, then it is set + to a value large enough to store the payload result and ``ENOSPC`` is + returned. + + .. note:: + + For string controls, this ``size`` field should + not be confused with the length of the string. This field refers + to the size of the memory that contains the string. The actual + *length* of the string may well be much smaller. + * - __u32 + - ``reserved2``\ [1] + - Reserved for future extensions. Drivers and applications must set + the array to zero. + * - union { + - (anonymous) + * - __s32 + - ``value`` + - New value or current value. Valid if this control is not of type + ``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is + not set. + * - __s64 + - ``value64`` + - New value or current value. Valid if this control is of type + ``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is + not set. + * - char * + - ``string`` + - A pointer to a string. Valid if this control is of type + ``V4L2_CTRL_TYPE_STRING``. + * - __u8 * + - ``p_u8`` + - A pointer to a matrix control of unsigned 8-bit values. Valid if + this control is of type ``V4L2_CTRL_TYPE_U8``. + * - __u16 * + - ``p_u16`` + - A pointer to a matrix control of unsigned 16-bit values. Valid if + this control is of type ``V4L2_CTRL_TYPE_U16``. + * - __u32 * + - ``p_u32`` + - A pointer to a matrix control of unsigned 32-bit values. Valid if + this control is of type ``V4L2_CTRL_TYPE_U32``. + * - struct :c:type:`v4l2_area` * + - ``p_area`` + - A pointer to a struct :c:type:`v4l2_area`. Valid if this control is + of type ``V4L2_CTRL_TYPE_AREA``. + * - struct :c:type:`v4l2_ctrl_h264_sps` * + - ``p_h264_sps`` + - A pointer to a struct :c:type:`v4l2_ctrl_h264_sps`. Valid if this control is + of type ``V4L2_CTRL_TYPE_H264_SPS``. + * - struct :c:type:`v4l2_ctrl_h264_pps` * + - ``p_h264_pps`` + - A pointer to a struct :c:type:`v4l2_ctrl_h264_pps`. Valid if this control is + of type ``V4L2_CTRL_TYPE_H264_PPS``. + * - struct :c:type:`v4l2_ctrl_h264_scaling_matrix` * + - ``p_h264_scaling_matrix`` + - A pointer to a struct :c:type:`v4l2_ctrl_h264_scaling_matrix`. Valid if this control is + of type ``V4L2_CTRL_TYPE_H264_SCALING_MATRIX``. + * - struct :c:type:`v4l2_ctrl_h264_pred_weights` * + - ``p_h264_pred_weights`` + - A pointer to a struct :c:type:`v4l2_ctrl_h264_pred_weights`. Valid if this control is + of type ``V4L2_CTRL_TYPE_H264_PRED_WEIGHTS``. + * - struct :c:type:`v4l2_ctrl_h264_slice_params` * + - ``p_h264_slice_params`` + - A pointer to a struct :c:type:`v4l2_ctrl_h264_slice_params`. Valid if this control is + of type ``V4L2_CTRL_TYPE_H264_SLICE_PARAMS``. + * - struct :c:type:`v4l2_ctrl_h264_decode_params` * + - ``p_h264_decode_params`` + - A pointer to a struct :c:type:`v4l2_ctrl_h264_decode_params`. Valid if this control is + of type ``V4L2_CTRL_TYPE_H264_DECODE_PARAMS``. + * - struct :c:type:`v4l2_ctrl_fwht_params` * + - ``p_fwht_params`` + - A pointer to a struct :c:type:`v4l2_ctrl_fwht_params`. Valid if this control is + of type ``V4L2_CTRL_TYPE_FWHT_PARAMS``. + * - struct :c:type:`v4l2_ctrl_vp8_frame` * + - ``p_vp8_frame`` + - A pointer to a struct :c:type:`v4l2_ctrl_vp8_frame`. Valid if this control is + of type ``V4L2_CTRL_TYPE_VP8_FRAME``. + * - struct :c:type:`v4l2_ctrl_mpeg2_sequence` * + - ``p_mpeg2_sequence`` + - A pointer to a struct :c:type:`v4l2_ctrl_mpeg2_sequence`. Valid if this control is + of type ``V4L2_CTRL_TYPE_MPEG2_SEQUENCE``. + * - struct :c:type:`v4l2_ctrl_mpeg2_picture` * + - ``p_mpeg2_picture`` + - A pointer to a struct :c:type:`v4l2_ctrl_mpeg2_picture`. Valid if this control is + of type ``V4L2_CTRL_TYPE_MPEG2_PICTURE``. + * - struct :c:type:`v4l2_ctrl_mpeg2_quantisation` * + - ``p_mpeg2_quantisation`` + - A pointer to a struct :c:type:`v4l2_ctrl_mpeg2_quantisation`. Valid if this control is + of type ``V4L2_CTRL_TYPE_MPEG2_QUANTISATION``. + * - struct :c:type:`v4l2_ctrl_vp9_compressed_hdr` * + - ``p_vp9_compressed_hdr_probs`` + - A pointer to a struct :c:type:`v4l2_ctrl_vp9_compressed_hdr`. Valid if this + control is of type ``V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR``. + * - struct :c:type:`v4l2_ctrl_vp9_frame` * + - ``p_vp9_frame`` + - A pointer to a struct :c:type:`v4l2_ctrl_vp9_frame`. Valid if this + control is of type ``V4L2_CTRL_TYPE_VP9_FRAME``. + * - struct :c:type:`v4l2_ctrl_hdr10_cll_info` * + - ``p_hdr10_cll`` + - A pointer to a struct :c:type:`v4l2_ctrl_hdr10_cll_info`. Valid if this control is + of type ``V4L2_CTRL_TYPE_HDR10_CLL_INFO``. + * - struct :c:type:`v4l2_ctrl_hdr10_mastering_display` * + - ``p_hdr10_mastering`` + - A pointer to a struct :c:type:`v4l2_ctrl_hdr10_mastering_display`. Valid if this control is + of type ``V4L2_CTRL_TYPE_HDR10_MASTERING_DISPLAY``. + * - struct :c:type:`v4l2_ctrl_hevc_sps` * + - ``p_hevc_sps`` + - A pointer to a struct :c:type:`v4l2_ctrl_hevc_sps`. Valid if this + control is of type ``V4L2_CTRL_TYPE_HEVC_SPS``. + * - struct :c:type:`v4l2_ctrl_hevc_pps` * + - ``p_hevc_pps`` + - A pointer to a struct :c:type:`v4l2_ctrl_hevc_pps`. Valid if this + control is of type ``V4L2_CTRL_TYPE_HEVC_PPS``. + * - struct :c:type:`v4l2_ctrl_hevc_slice_params` * + - ``p_hevc_slice_params`` + - A pointer to a struct :c:type:`v4l2_ctrl_hevc_slice_params`. Valid if this + control is of type ``V4L2_CTRL_TYPE_HEVC_SLICE_PARAMS``. + * - struct :c:type:`v4l2_ctrl_hevc_scaling_matrix` * + - ``p_hevc_scaling_matrix`` + - A pointer to a struct :c:type:`v4l2_ctrl_hevc_scaling_matrix`. Valid if this + control is of type ``V4L2_CTRL_TYPE_HEVC_SCALING_MATRIX``. + * - struct :c:type:`v4l2_ctrl_hevc_decode_params` * + - ``p_hevc_decode_params`` + - A pointer to a struct :c:type:`v4l2_ctrl_hevc_decode_params`. Valid if this + control is of type ``V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS``. + * - void * + - ``ptr`` + - A pointer to a compound type which can be an N-dimensional array + and/or a compound type (the control's type is >= + ``V4L2_CTRL_COMPOUND_TYPES``). Valid if + ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set for this control. + * - } + - + +.. raw:: latex + + \normalsize + +.. tabularcolumns:: |p{4.0cm}|p{2.5cm}|p{10.8cm}| + +.. c:type:: v4l2_ext_controls + +.. cssclass:: longtable + +.. flat-table:: struct v4l2_ext_controls + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - union { + - (anonymous) + * - __u32 + - ``which`` + - Which value of the control to get/set/try. + * - :cspan:`2` ``V4L2_CTRL_WHICH_CUR_VAL`` will return the current value of + the control, ``V4L2_CTRL_WHICH_DEF_VAL`` will return the default + value of the control and ``V4L2_CTRL_WHICH_REQUEST_VAL`` indicates that + these controls have to be retrieved from a request or tried/set for + a request. In the latter case the ``request_fd`` field contains the + file descriptor of the request that should be used. If the device + does not support requests, then ``EACCES`` will be returned. + + When using ``V4L2_CTRL_WHICH_DEF_VAL`` be aware that you can only + get the default value of the control, you cannot set or try it. + + For backwards compatibility you can also use a control class here + (see :ref:`ctrl-class`). In that case all controls have to + belong to that control class. This usage is deprecated, instead + just use ``V4L2_CTRL_WHICH_CUR_VAL``. There are some very old + drivers that do not yet support ``V4L2_CTRL_WHICH_CUR_VAL`` and + that require a control class here. You can test for such drivers + by setting ``which`` to ``V4L2_CTRL_WHICH_CUR_VAL`` and calling + :ref:`VIDIOC_TRY_EXT_CTRLS ` with a count of 0. + If that fails, then the driver does not support ``V4L2_CTRL_WHICH_CUR_VAL``. + * - __u32 + - ``ctrl_class`` + - Deprecated name kept for backwards compatibility. Use ``which`` instead. + * - } + - + * - __u32 + - ``count`` + - The number of controls in the controls array. May also be zero. + * - __u32 + - ``error_idx`` + - Index of the failing control. Set by the driver in case of an error. + * - :cspan:`2` If the error is associated + with a particular control, then ``error_idx`` is set to the index + of that control. If the error is not related to a specific + control, or the validation step failed (see below), then + ``error_idx`` is set to ``count``. The value is undefined if the + ioctl returned 0 (success). + + Before controls are read from/written to hardware a validation + step takes place: this checks if all controls in the list are + valid controls, if no attempt is made to write to a read-only + control or read from a write-only control, and any other up-front + checks that can be done without accessing the hardware. The exact + validations done during this step are driver dependent since some + checks might require hardware access for some devices, thus making + it impossible to do those checks up-front. However, drivers should + make a best-effort to do as many up-front checks as possible. + + This check is done to avoid leaving the hardware in an + inconsistent state due to easy-to-avoid problems. But it leads to + another problem: the application needs to know whether an error + came from the validation step (meaning that the hardware was not + touched) or from an error during the actual reading from/writing + to hardware. + + The, in hindsight quite poor, solution for that is to set + ``error_idx`` to ``count`` if the validation failed. This has the + unfortunate side-effect that it is not possible to see which + control failed the validation. If the validation was successful + and the error happened while accessing the hardware, then + ``error_idx`` is less than ``count`` and only the controls up to + ``error_idx-1`` were read or written correctly, and the state of + the remaining controls is undefined. + + Since :ref:`VIDIOC_TRY_EXT_CTRLS ` does not access hardware there is + also no need to handle the validation step in this special way, so + ``error_idx`` will just be set to the control that failed the + validation step instead of to ``count``. This means that if + :ref:`VIDIOC_S_EXT_CTRLS ` fails with ``error_idx`` set to ``count``, + then you can call :ref:`VIDIOC_TRY_EXT_CTRLS ` to try to discover the + actual control that failed the validation step. Unfortunately, + there is no ``TRY`` equivalent for :ref:`VIDIOC_G_EXT_CTRLS `. + * - __s32 + - ``request_fd`` + - File descriptor of the request to be used by this operation. Only + valid if ``which`` is set to ``V4L2_CTRL_WHICH_REQUEST_VAL``. + If the device does not support requests, then ``EACCES`` will be returned. + If requests are supported but an invalid request file descriptor is + given, then ``EINVAL`` will be returned. + * - __u32 + - ``reserved``\ [1] + - Reserved for future extensions. + + Drivers and applications must set the array to zero. + * - struct :c:type:`v4l2_ext_control` * + - ``controls`` + - Pointer to an array of ``count`` v4l2_ext_control structures. + + Ignored if ``count`` equals zero. + +.. tabularcolumns:: |p{7.3cm}|p{2.0cm}|p{8.0cm}| + +.. cssclass:: longtable + +.. _ctrl-class: + +.. flat-table:: Control classes + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + * - ``V4L2_CTRL_CLASS_USER`` + - 0x980000 + - The class containing user controls. These controls are described + in :ref:`control`. All controls that can be set using the + :ref:`VIDIOC_S_CTRL ` and + :ref:`VIDIOC_G_CTRL ` ioctl belong to this + class. + * - ``V4L2_CTRL_CLASS_CODEC`` + - 0x990000 + - The class containing stateful codec controls. These controls are + described in :ref:`codec-controls`. + * - ``V4L2_CTRL_CLASS_CAMERA`` + - 0x9a0000 + - The class containing camera controls. These controls are described + in :ref:`camera-controls`. + * - ``V4L2_CTRL_CLASS_FM_TX`` + - 0x9b0000 + - The class containing FM Transmitter (FM TX) controls. These + controls are described in :ref:`fm-tx-controls`. + * - ``V4L2_CTRL_CLASS_FLASH`` + - 0x9c0000 + - The class containing flash device controls. These controls are + described in :ref:`flash-controls`. + * - ``V4L2_CTRL_CLASS_JPEG`` + - 0x9d0000 + - The class containing JPEG compression controls. These controls are + described in :ref:`jpeg-controls`. + * - ``V4L2_CTRL_CLASS_IMAGE_SOURCE`` + - 0x9e0000 + - The class containing image source controls. These controls are + described in :ref:`image-source-controls`. + * - ``V4L2_CTRL_CLASS_IMAGE_PROC`` + - 0x9f0000 + - The class containing image processing controls. These controls are + described in :ref:`image-process-controls`. + * - ``V4L2_CTRL_CLASS_FM_RX`` + - 0xa10000 + - The class containing FM Receiver (FM RX) controls. These controls + are described in :ref:`fm-rx-controls`. + * - ``V4L2_CTRL_CLASS_RF_TUNER`` + - 0xa20000 + - The class containing RF tuner controls. These controls are + described in :ref:`rf-tuner-controls`. + * - ``V4L2_CTRL_CLASS_DETECT`` + - 0xa30000 + - The class containing motion or object detection controls. These controls + are described in :ref:`detect-controls`. + * - ``V4L2_CTRL_CLASS_CODEC_STATELESS`` + - 0xa40000 + - The class containing stateless codec controls. These controls are + described in :ref:`codec-stateless-controls`. + * - ``V4L2_CTRL_CLASS_COLORIMETRY`` + - 0xa50000 + - The class containing colorimetry controls. These controls are + described in :ref:`colorimetry-controls`. + +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. + +EINVAL + The struct :c:type:`v4l2_ext_control` ``id`` is + invalid, or the struct :c:type:`v4l2_ext_controls` + ``which`` is invalid, or the struct + :c:type:`v4l2_ext_control` ``value`` was + inappropriate (e.g. the given menu index is not supported by the + driver), or the ``which`` field was set to ``V4L2_CTRL_WHICH_REQUEST_VAL`` + but the given ``request_fd`` was invalid or ``V4L2_CTRL_WHICH_REQUEST_VAL`` + is not supported by the kernel. + This error code is also returned by the + :ref:`VIDIOC_S_EXT_CTRLS ` and :ref:`VIDIOC_TRY_EXT_CTRLS ` ioctls if two or + more control values are in conflict. + +ERANGE + The struct :c:type:`v4l2_ext_control` ``value`` + is out of bounds. + +EBUSY + The control is temporarily not changeable, possibly because another + applications took over control of the device function this control + belongs to, or (if the ``which`` field was set to + ``V4L2_CTRL_WHICH_REQUEST_VAL``) the request was queued but not yet + completed. + +ENOSPC + The space reserved for the control's payload is insufficient. The + field ``size`` is set to a value that is enough to store the payload + and this error code is returned. + +EACCES + Attempt to try or set a read-only control, or to get a write-only + control, or to get a control from a request that has not yet been + completed. + + Or the ``which`` field was set to ``V4L2_CTRL_WHICH_REQUEST_VAL`` but the + device does not support requests. + + Or if there is an attempt to set an inactive control and the driver is + not capable of caching the new value until the control is active again. -- cgit v1.2.3