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().
  ...

1 files changed, 488 insertions, 0 deletions

diff --git a/Documentation/gpu/komeda-kms.rst b/Documentation/gpu/komeda-kms.rst
new file mode 100644
index 000000000..eb693c857
--- /dev/null
+++ b/Documentation/gpu/komeda-kms.rst
@@ -0,0 +1,488 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============================
+ drm/komeda Arm display driver
+==============================
+
+The drm/komeda driver supports the Arm display processor D71 and later products,
+this document gives a brief overview of driver design: how it works and why
+design it like that.
+
+Overview of D71 like display IPs
+================================
+
+From D71, Arm display IP begins to adopt a flexible and modularized
+architecture. A display pipeline is made up of multiple individual and
+functional pipeline stages called components, and every component has some
+specific capabilities that can give the flowed pipeline pixel data a
+particular processing.
+
+Typical D71 components:
+
+Layer
+-----
+Layer is the first pipeline stage, which prepares the pixel data for the next
+stage. It fetches the pixel from memory, decodes it if it's AFBC, rotates the
+source image, unpacks or converts YUV pixels to the device internal RGB pixels,
+then adjusts the color_space of pixels if needed.
+
+Scaler
+------
+As its name suggests, scaler takes responsibility for scaling, and D71 also
+supports image enhancements by scaler.
+The usage of scaler is very flexible and can be connected to layer output
+for layer scaling, or connected to compositor and scale the whole display
+frame and then feed the output data into wb_layer which will then write it
+into memory.
+
+Compositor (compiz)
+-------------------
+Compositor blends multiple layers or pixel data flows into one single display
+frame. its output frame can be fed into post image processor for showing it on
+the monitor or fed into wb_layer and written to memory at the same time.
+user can also insert a scaler between compositor and wb_layer to down scale
+the display frame first and then write to memory.
+
+Writeback Layer (wb_layer)
+--------------------------
+Writeback layer does the opposite things of Layer, which connects to compiz
+and writes the composition result to memory.
+
+Post image processor (improc)
+-----------------------------
+Post image processor adjusts frame data like gamma and color space to fit the
+requirements of the monitor.
+
+Timing controller (timing_ctrlr)
+--------------------------------
+Final stage of display pipeline, Timing controller is not for the pixel
+handling, but only for controlling the display timing.
+
+Merger
+------
+D71 scaler mostly only has the half horizontal input/output capabilities
+compared with Layer, like if Layer supports 4K input size, the scaler only can
+support 2K input/output in the same time. To achieve the ful frame scaling, D71
+introduces Layer Split, which splits the whole image to two half parts and feeds
+them to two Layers A and B, and does the scaling independently. After scaling
+the result need to be fed to merger to merge two part images together, and then
+output merged result to compiz.
+
+Splitter
+--------
+Similar to Layer Split, but Splitter is used for writeback, which splits the
+compiz result to two parts and then feed them to two scalers.
+
+Possible D71 Pipeline usage
+===========================
+
+Benefitting from the modularized architecture, D71 pipelines can be easily
+adjusted to fit different usages. And D71 has two pipelines, which support two
+types of working mode:
+
+-   Dual display mode
+    Two pipelines work independently and separately to drive two display outputs.
+
+-   Single display mode
+    Two pipelines work together to drive only one display output.
+
+    On this mode, pipeline_B doesn't work indenpendently, but outputs its
+    composition result into pipeline_A, and its pixel timing also derived from
+    pipeline_A.timing_ctrlr. The pipeline_B works just like a "slave" of
+    pipeline_A(master)
+
+Single pipeline data flow
+-------------------------
+
+.. kernel-render:: DOT
+   :alt: Single pipeline digraph
+   :caption: Single pipeline data flow
+
+   digraph single_ppl {
+      rankdir=LR;
+
+      subgraph {
+         "Memory";
+         "Monitor";
+      }
+
+      subgraph cluster_pipeline {
+          style=dashed
+          node [shape=box]
+          {
+              node [bgcolor=grey style=dashed]
+              "Scaler-0";
+              "Scaler-1";
+              "Scaler-0/1"
+          }
+
+         node [bgcolor=grey style=filled]
+         "Layer-0" -> "Scaler-0"
+         "Layer-1" -> "Scaler-0"
+         "Layer-2" -> "Scaler-1"
+         "Layer-3" -> "Scaler-1"
+
+         "Layer-0" -> "Compiz"
+         "Layer-1" -> "Compiz"
+         "Layer-2" -> "Compiz"
+         "Layer-3" -> "Compiz"
+         "Scaler-0" -> "Compiz"
+         "Scaler-1" -> "Compiz"
+
+         "Compiz" -> "Scaler-0/1" -> "Wb_layer"
+         "Compiz" -> "Improc" -> "Timing Controller"
+      }
+
+      "Wb_layer" -> "Memory"
+      "Timing Controller" -> "Monitor"
+   }
+
+Dual pipeline with Slave enabled
+--------------------------------
+
+.. kernel-render:: DOT
+   :alt: Slave pipeline digraph
+   :caption: Slave pipeline enabled data flow
+
+   digraph slave_ppl {
+      rankdir=LR;
+
+      subgraph {
+         "Memory";
+         "Monitor";
+      }
+      node [shape=box]
+      subgraph cluster_pipeline_slave {
+          style=dashed
+          label="Slave Pipeline_B"
+          node [shape=box]
+          {
+              node [bgcolor=grey style=dashed]
+              "Slave.Scaler-0";
+              "Slave.Scaler-1";
+          }
+
+         node [bgcolor=grey style=filled]
+         "Slave.Layer-0" -> "Slave.Scaler-0"
+         "Slave.Layer-1" -> "Slave.Scaler-0"
+         "Slave.Layer-2" -> "Slave.Scaler-1"
+         "Slave.Layer-3" -> "Slave.Scaler-1"
+
+         "Slave.Layer-0" -> "Slave.Compiz"
+         "Slave.Layer-1" -> "Slave.Compiz"
+         "Slave.Layer-2" -> "Slave.Compiz"
+         "Slave.Layer-3" -> "Slave.Compiz"
+         "Slave.Scaler-0" -> "Slave.Compiz"
+         "Slave.Scaler-1" -> "Slave.Compiz"
+      }
+
+      subgraph cluster_pipeline_master {
+          style=dashed
+          label="Master Pipeline_A"
+          node [shape=box]
+          {
+              node [bgcolor=grey style=dashed]
+              "Scaler-0";
+              "Scaler-1";
+              "Scaler-0/1"
+          }
+
+         node [bgcolor=grey style=filled]
+         "Layer-0" -> "Scaler-0"
+         "Layer-1" -> "Scaler-0"
+         "Layer-2" -> "Scaler-1"
+         "Layer-3" -> "Scaler-1"
+
+         "Slave.Compiz" -> "Compiz"
+         "Layer-0" -> "Compiz"
+         "Layer-1" -> "Compiz"
+         "Layer-2" -> "Compiz"
+         "Layer-3" -> "Compiz"
+         "Scaler-0" -> "Compiz"
+         "Scaler-1" -> "Compiz"
+
+         "Compiz" -> "Scaler-0/1" -> "Wb_layer"
+         "Compiz" -> "Improc" -> "Timing Controller"
+      }
+
+      "Wb_layer" -> "Memory"
+      "Timing Controller" -> "Monitor"
+   }
+
+Sub-pipelines for input and output
+----------------------------------
+
+A complete display pipeline can be easily divided into three sub-pipelines
+according to the in/out usage.
+
+Layer(input) pipeline
+~~~~~~~~~~~~~~~~~~~~~
+
+.. kernel-render:: DOT
+   :alt: Layer data digraph
+   :caption: Layer (input) data flow
+
+   digraph layer_data_flow {
+      rankdir=LR;
+      node [shape=box]
+
+      {
+         node [bgcolor=grey style=dashed]
+           "Scaler-n";
+      }
+
+      "Layer-n" -> "Scaler-n" -> "Compiz"
+   }
+
+.. kernel-render:: DOT
+   :alt: Layer Split digraph
+   :caption: Layer Split pipeline
+
+   digraph layer_data_flow {
+      rankdir=LR;
+      node [shape=box]
+
+      "Layer-0/1" -> "Scaler-0" -> "Merger"
+      "Layer-2/3" -> "Scaler-1" -> "Merger"
+      "Merger" -> "Compiz"
+   }
+
+Writeback(output) pipeline
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+.. kernel-render:: DOT
+   :alt: writeback digraph
+   :caption: Writeback(output) data flow
+
+   digraph writeback_data_flow {
+      rankdir=LR;
+      node [shape=box]
+
+      {
+         node [bgcolor=grey style=dashed]
+           "Scaler-n";
+      }
+
+      "Compiz" -> "Scaler-n" -> "Wb_layer"
+   }
+
+.. kernel-render:: DOT
+   :alt: split writeback digraph
+   :caption: Writeback(output) Split data flow
+
+   digraph writeback_data_flow {
+      rankdir=LR;
+      node [shape=box]
+
+      "Compiz" -> "Splitter"
+      "Splitter" -> "Scaler-0" -> "Merger"
+      "Splitter" -> "Scaler-1" -> "Merger"
+      "Merger" -> "Wb_layer"
+   }
+
+Display output pipeline
+~~~~~~~~~~~~~~~~~~~~~~~
+.. kernel-render:: DOT
+   :alt: display digraph
+   :caption: display output data flow
+
+   digraph single_ppl {
+      rankdir=LR;
+      node [shape=box]
+
+      "Compiz" -> "Improc" -> "Timing Controller"
+   }
+
+In the following section we'll see these three sub-pipelines will be handled
+by KMS-plane/wb_conn/crtc respectively.
+
+Komeda Resource abstraction
+===========================
+
+struct komeda_pipeline/component
+--------------------------------
+
+To fully utilize and easily access/configure the HW, the driver side also uses
+a similar architecture: Pipeline/Component to describe the HW features and
+capabilities, and a specific component includes two parts:
+
+-  Data flow controlling.
+-  Specific component capabilities and features.
+
+So the driver defines a common header struct komeda_component to describe the
+data flow control and all specific components are a subclass of this base
+structure.
+
+.. kernel-doc:: drivers/gpu/drm/arm/display/komeda/komeda_pipeline.h
+   :internal:
+
+Resource discovery and initialization
+=====================================
+
+Pipeline and component are used to describe how to handle the pixel data. We
+still need a @struct komeda_dev to describe the whole view of the device, and
+the control-abilites of device.
+
+We have &komeda_dev, &komeda_pipeline, &komeda_component. Now fill devices with
+pipelines. Since komeda is not for D71 only but also intended for later products,
+of course we’d better share as much as possible between different products. To
+achieve this, split the komeda device into two layers: CORE and CHIP.
+
+-   CORE: for common features and capabilities handling.
+-   CHIP: for register programing and HW specific feature (limitation) handling.
+
+CORE can access CHIP by three chip function structures:
+
+-   struct komeda_dev_funcs
+-   struct komeda_pipeline_funcs
+-   struct komeda_component_funcs
+
+.. kernel-doc:: drivers/gpu/drm/arm/display/komeda/komeda_dev.h
+   :internal:
+
+Format handling
+===============
+
+.. kernel-doc:: drivers/gpu/drm/arm/display/komeda/komeda_format_caps.h
+   :internal:
+.. kernel-doc:: drivers/gpu/drm/arm/display/komeda/komeda_framebuffer.h
+   :internal:
+
+Attach komeda_dev to DRM-KMS
+============================
+
+Komeda abstracts resources by pipeline/component, but DRM-KMS uses
+crtc/plane/connector. One KMS-obj cannot represent only one single component,
+since the requirements of a single KMS object cannot simply be achieved by a
+single component, usually that needs multiple components to fit the requirement.
+Like set mode, gamma, ctm for KMS all target on CRTC-obj, but komeda needs
+compiz, improc and timing_ctrlr to work together to fit these requirements.
+And a KMS-Plane may require multiple komeda resources: layer/scaler/compiz.
+
+So, one KMS-Obj represents a sub-pipeline of komeda resources.
+
+-   Plane: `Layer(input) pipeline`_
+-   Wb_connector: `Writeback(output) pipeline`_
+-   Crtc: `Display output pipeline`_
+
+So, for komeda, we treat KMS crtc/plane/connector as users of pipeline and
+component, and at any one time a pipeline/component only can be used by one
+user. And pipeline/component will be treated as private object of DRM-KMS; the
+state will be managed by drm_atomic_state as well.
+
+How to map plane to Layer(input) pipeline
+-----------------------------------------
+
+Komeda has multiple Layer input pipelines, see:
+-   `Single pipeline data flow`_
+-   `Dual pipeline with Slave enabled`_
+
+The easiest way is binding a plane to a fixed Layer pipeline, but consider the
+komeda capabilities:
+
+-   Layer Split, See `Layer(input) pipeline`_
+
+    Layer_Split is quite complicated feature, which splits a big image into two
+    parts and handles it by two layers and two scalers individually. But it
+    imports an edge problem or effect in the middle of the image after the split.
+    To avoid such a problem, it needs a complicated Split calculation and some
+    special configurations to the layer and scaler. We'd better hide such HW
+    related complexity to user mode.
+
+-   Slave pipeline, See `Dual pipeline with Slave enabled`_
+
+    Since the compiz component doesn't output alpha value, the slave pipeline
+    only can be used for bottom layers composition. The komeda driver wants to
+    hide this limitation to the user. The way to do this is to pick a suitable
+    Layer according to plane_state->zpos.
+
+So for komeda, the KMS-plane doesn't represent a fixed komeda layer pipeline,
+but multiple Layers with same capabilities. Komeda will select one or more
+Layers to fit the requirement of one KMS-plane.
+
+Make component/pipeline to be drm_private_obj
+---------------------------------------------
+
+Add :c:type:`drm_private_obj` to :c:type:`komeda_component`, :c:type:`komeda_pipeline`
+
+.. code-block:: c
+
+    struct komeda_component {
+        struct drm_private_obj obj;
+        ...
+    }
+
+    struct komeda_pipeline {
+        struct drm_private_obj obj;
+        ...
+    }
+
+Tracking component_state/pipeline_state by drm_atomic_state
+-----------------------------------------------------------
+
+Add :c:type:`drm_private_state` and user to :c:type:`komeda_component_state`,
+:c:type:`komeda_pipeline_state`
+
+.. code-block:: c
+
+    struct komeda_component_state {
+        struct drm_private_state obj;
+        void *binding_user;
+        ...
+    }
+
+    struct komeda_pipeline_state {
+        struct drm_private_state obj;
+        struct drm_crtc *crtc;
+        ...
+    }
+
+komeda component validation
+---------------------------
+
+Komeda has multiple types of components, but the process of validation are
+similar, usually including the following steps:
+
+.. code-block:: c
+
+    int komeda_xxxx_validate(struct komeda_component_xxx xxx_comp,
+                struct komeda_component_output *input_dflow,
+                struct drm_plane/crtc/connector *user,
+                struct drm_plane/crtc/connector_state, *user_state)
+    {
+         setup 1: check if component is needed, like the scaler is optional depending
+                  on the user_state; if unneeded, just return, and the caller will
+                  put the data flow into next stage.
+         Setup 2: check user_state with component features and capabilities to see
+                  if requirements can be met; if not, return fail.
+         Setup 3: get component_state from drm_atomic_state, and try set to set
+                  user to component; fail if component has been assigned to another
+                  user already.
+         Setup 3: configure the component_state, like set its input component,
+                  convert user_state to component specific state.
+         Setup 4: adjust the input_dflow and prepare it for the next stage.
+    }
+
+komeda_kms Abstraction
+----------------------
+
+.. kernel-doc:: drivers/gpu/drm/arm/display/komeda/komeda_kms.h
+   :internal:
+
+komde_kms Functions
+-------------------
+.. kernel-doc:: drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
+   :internal:
+.. kernel-doc:: drivers/gpu/drm/arm/display/komeda/komeda_plane.c
+   :internal:
+
+Build komeda to be a Linux module driver
+========================================
+
+Now we have two level devices:
+
+-   komeda_dev: describes the real display hardware.
+-   komeda_kms_dev: attachs or connects komeda_dev to DRM-KMS.
+
+All komeda operations are supplied or operated by komeda_dev or komeda_kms_dev,
+the module driver is only a simple wrapper to pass the Linux command
+(probe/remove/pm) into komeda_dev or komeda_kms_dev.