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(). ... --- Documentation/fb/framebuffer.rst | 353 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 353 insertions(+) create mode 100644 Documentation/fb/framebuffer.rst (limited to 'Documentation/fb/framebuffer.rst') diff --git a/Documentation/fb/framebuffer.rst b/Documentation/fb/framebuffer.rst new file mode 100644 index 000000000..7fe087310 --- /dev/null +++ b/Documentation/fb/framebuffer.rst @@ -0,0 +1,353 @@ +======================= +The Frame Buffer Device +======================= + +Last revised: May 10, 2001 + + +0. Introduction +--------------- + +The frame buffer device provides an abstraction for the graphics hardware. It +represents the frame buffer of some video hardware and allows application +software to access the graphics hardware through a well-defined interface, so +the software doesn't need to know anything about the low-level (hardware +register) stuff. + +The device is accessed through special device nodes, usually located in the +/dev directory, i.e. /dev/fb*. + + +1. User's View of /dev/fb* +-------------------------- + +From the user's point of view, the frame buffer device looks just like any +other device in /dev. It's a character device using major 29; the minor +specifies the frame buffer number. + +By convention, the following device nodes are used (numbers indicate the device +minor numbers):: + + 0 = /dev/fb0 First frame buffer + 1 = /dev/fb1 Second frame buffer + ... + 31 = /dev/fb31 32nd frame buffer + +For backwards compatibility, you may want to create the following symbolic +links:: + + /dev/fb0current -> fb0 + /dev/fb1current -> fb1 + +and so on... + +The frame buffer devices are also `normal` memory devices, this means, you can +read and write their contents. You can, for example, make a screen snapshot by:: + + cp /dev/fb0 myfile + +There also can be more than one frame buffer at a time, e.g. if you have a +graphics card in addition to the built-in hardware. The corresponding frame +buffer devices (/dev/fb0 and /dev/fb1 etc.) work independently. + +Application software that uses the frame buffer device (e.g. the X server) will +use /dev/fb0 by default (older software uses /dev/fb0current). You can specify +an alternative frame buffer device by setting the environment variable +$FRAMEBUFFER to the path name of a frame buffer device, e.g. (for sh/bash +users):: + + export FRAMEBUFFER=/dev/fb1 + +or (for csh users):: + + setenv FRAMEBUFFER /dev/fb1 + +After this the X server will use the second frame buffer. + + +2. Programmer's View of /dev/fb* +-------------------------------- + +As you already know, a frame buffer device is a memory device like /dev/mem and +it has the same features. You can read it, write it, seek to some location in +it and mmap() it (the main usage). The difference is just that the memory that +appears in the special file is not the whole memory, but the frame buffer of +some video hardware. + +/dev/fb* also allows several ioctls on it, by which lots of information about +the hardware can be queried and set. The color map handling works via ioctls, +too. Look into for more information on what ioctls exist and on +which data structures they work. Here's just a brief overview: + + - You can request unchangeable information about the hardware, like name, + organization of the screen memory (planes, packed pixels, ...) and address + and length of the screen memory. + + - You can request and change variable information about the hardware, like + visible and virtual geometry, depth, color map format, timing, and so on. + If you try to change that information, the driver maybe will round up some + values to meet the hardware's capabilities (or return EINVAL if that isn't + possible). + + - You can get and set parts of the color map. Communication is done with 16 + bits per color part (red, green, blue, transparency) to support all + existing hardware. The driver does all the computations needed to apply + it to the hardware (round it down to less bits, maybe throw away + transparency). + +All this hardware abstraction makes the implementation of application programs +easier and more portable. E.g. the X server works completely on /dev/fb* and +thus doesn't need to know, for example, how the color registers of the concrete +hardware are organized. XF68_FBDev is a general X server for bitmapped, +unaccelerated video hardware. The only thing that has to be built into +application programs is the screen organization (bitplanes or chunky pixels +etc.), because it works on the frame buffer image data directly. + +For the future it is planned that frame buffer drivers for graphics cards and +the like can be implemented as kernel modules that are loaded at runtime. Such +a driver just has to call register_framebuffer() and supply some functions. +Writing and distributing such drivers independently from the kernel will save +much trouble... + + +3. Frame Buffer Resolution Maintenance +-------------------------------------- + +Frame buffer resolutions are maintained using the utility `fbset`. It can +change the video mode properties of a frame buffer device. Its main usage is +to change the current video mode, e.g. during boot up in one of your `/etc/rc.*` +or `/etc/init.d/*` files. + +Fbset uses a video mode database stored in a configuration file, so you can +easily add your own modes and refer to them with a simple identifier. + + +4. The X Server +--------------- + +The X server (XF68_FBDev) is the most notable application program for the frame +buffer device. Starting with XFree86 release 3.2, the X server is part of +XFree86 and has 2 modes: + + - If the `Display` subsection for the `fbdev` driver in the /etc/XF86Config + file contains a:: + + Modes "default" + + line, the X server will use the scheme discussed above, i.e. it will start + up in the resolution determined by /dev/fb0 (or $FRAMEBUFFER, if set). You + still have to specify the color depth (using the Depth keyword) and virtual + resolution (using the Virtual keyword) though. This is the default for the + configuration file supplied with XFree86. It's the most simple + configuration, but it has some limitations. + + - Therefore it's also possible to specify resolutions in the /etc/XF86Config + file. This allows for on-the-fly resolution switching while retaining the + same virtual desktop size. The frame buffer device that's used is still + /dev/fb0current (or $FRAMEBUFFER), but the available resolutions are + defined by /etc/XF86Config now. The disadvantage is that you have to + specify the timings in a different format (but `fbset -x` may help). + +To tune a video mode, you can use fbset or xvidtune. Note that xvidtune doesn't +work 100% with XF68_FBDev: the reported clock values are always incorrect. + + +5. Video Mode Timings +--------------------- + +A monitor draws an image on the screen by using an electron beam (3 electron +beams for color models, 1 electron beam for monochrome monitors). The front of +the screen is covered by a pattern of colored phosphors (pixels). If a phosphor +is hit by an electron, it emits a photon and thus becomes visible. + +The electron beam draws horizontal lines (scanlines) from left to right, and +from the top to the bottom of the screen. By modifying the intensity of the +electron beam, pixels with various colors and intensities can be shown. + +After each scanline the electron beam has to move back to the left side of the +screen and to the next line: this is called the horizontal retrace. After the +whole screen (frame) was painted, the beam moves back to the upper left corner: +this is called the vertical retrace. During both the horizontal and vertical +retrace, the electron beam is turned off (blanked). + +The speed at which the electron beam paints the pixels is determined by the +dotclock in the graphics board. For a dotclock of e.g. 28.37516 MHz (millions +of cycles per second), each pixel is 35242 ps (picoseconds) long:: + + 1/(28.37516E6 Hz) = 35.242E-9 s + +If the screen resolution is 640x480, it will take:: + + 640*35.242E-9 s = 22.555E-6 s + +to paint the 640 (xres) pixels on one scanline. But the horizontal retrace +also takes time (e.g. 272 `pixels`), so a full scanline takes:: + + (640+272)*35.242E-9 s = 32.141E-6 s + +We'll say that the horizontal scanrate is about 31 kHz:: + + 1/(32.141E-6 s) = 31.113E3 Hz + +A full screen counts 480 (yres) lines, but we have to consider the vertical +retrace too (e.g. 49 `lines`). So a full screen will take:: + + (480+49)*32.141E-6 s = 17.002E-3 s + +The vertical scanrate is about 59 Hz:: + + 1/(17.002E-3 s) = 58.815 Hz + +This means the screen data is refreshed about 59 times per second. To have a +stable picture without visible flicker, VESA recommends a vertical scanrate of +at least 72 Hz. But the perceived flicker is very human dependent: some people +can use 50 Hz without any trouble, while I'll notice if it's less than 80 Hz. + +Since the monitor doesn't know when a new scanline starts, the graphics board +will supply a synchronization pulse (horizontal sync or hsync) for each +scanline. Similarly it supplies a synchronization pulse (vertical sync or +vsync) for each new frame. The position of the image on the screen is +influenced by the moments at which the synchronization pulses occur. + +The following picture summarizes all timings. The horizontal retrace time is +the sum of the left margin, the right margin and the hsync length, while the +vertical retrace time is the sum of the upper margin, the lower margin and the +vsync length:: + + +----------+---------------------------------------------+----------+-------+ + | | ↑ | | | + | | |upper_margin | | | + | | ↓ | | | + +----------###############################################----------+-------+ + | # ↑ # | | + | # | # | | + | # | # | | + | # | # | | + | left # | # right | hsync | + | margin # | xres # margin | len | + |<-------->#<---------------+--------------------------->#<-------->|<----->| + | # | # | | + | # | # | | + | # | # | | + | # |yres # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # ↓ # | | + +----------###############################################----------+-------+ + | | ↑ | | | + | | |lower_margin | | | + | | ↓ | | | + +----------+---------------------------------------------+----------+-------+ + | | ↑ | | | + | | |vsync_len | | | + | | ↓ | | | + +----------+---------------------------------------------+----------+-------+ + +The frame buffer device expects all horizontal timings in number of dotclocks +(in picoseconds, 1E-12 s), and vertical timings in number of scanlines. + + +6. Converting XFree86 timing values info frame buffer device timings +-------------------------------------------------------------------- + +An XFree86 mode line consists of the following fields:: + + "800x600" 50 800 856 976 1040 600 637 643 666 + < name > DCF HR SH1 SH2 HFL VR SV1 SV2 VFL + +The frame buffer device uses the following fields: + + - pixclock: pixel clock in ps (pico seconds) + - left_margin: time from sync to picture + - right_margin: time from picture to sync + - upper_margin: time from sync to picture + - lower_margin: time from picture to sync + - hsync_len: length of horizontal sync + - vsync_len: length of vertical sync + +1) Pixelclock: + + xfree: in MHz + + fb: in picoseconds (ps) + + pixclock = 1000000 / DCF + +2) horizontal timings: + + left_margin = HFL - SH2 + + right_margin = SH1 - HR + + hsync_len = SH2 - SH1 + +3) vertical timings: + + upper_margin = VFL - SV2 + + lower_margin = SV1 - VR + + vsync_len = SV2 - SV1 + +Good examples for VESA timings can be found in the XFree86 source tree, +under "xc/programs/Xserver/hw/xfree86/doc/modeDB.txt". + + +7. References +------------- + +For more specific information about the frame buffer device and its +applications, please refer to the Linux-fbdev website: + + http://linux-fbdev.sourceforge.net/ + +and to the following documentation: + + - The manual pages for fbset: fbset(8), fb.modes(5) + - The manual pages for XFree86: XF68_FBDev(1), XF86Config(4/5) + - The mighty kernel sources: + + - linux/drivers/video/ + - linux/include/linux/fb.h + - linux/include/video/ + + + +8. Mailing list +--------------- + +There is a frame buffer device related mailing list at kernel.org: +linux-fbdev@vger.kernel.org. + +Point your web browser to http://sourceforge.net/projects/linux-fbdev/ for +subscription information and archive browsing. + + +9. Downloading +-------------- + +All necessary files can be found at + + ftp://ftp.uni-erlangen.de/pub/Linux/LOCAL/680x0/ + +and on its mirrors. + +The latest version of fbset can be found at + + http://www.linux-fbdev.org/ + + +10. Credits +----------- + +This readme was written by Geert Uytterhoeven, partly based on the original +`X-framebuffer.README` by Roman Hodek and Martin Schaller. Section 6 was +provided by Frank Neumann. + +The frame buffer device abstraction was designed by Martin Schaller. -- cgit v1.2.3