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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/driver-api/driver-model/driver.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to '')
-rw-r--r-- | Documentation/driver-api/driver-model/driver.rst | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/Documentation/driver-api/driver-model/driver.rst b/Documentation/driver-api/driver-model/driver.rst new file mode 100644 index 000000000..06f818b1d --- /dev/null +++ b/Documentation/driver-api/driver-model/driver.rst @@ -0,0 +1,286 @@ +============== +Device Drivers +============== + +See the kerneldoc for the struct device_driver. + +Allocation +~~~~~~~~~~ + +Device drivers are statically allocated structures. Though there may +be multiple devices in a system that a driver supports, struct +device_driver represents the driver as a whole (not a particular +device instance). + +Initialization +~~~~~~~~~~~~~~ + +The driver must initialize at least the name and bus fields. It should +also initialize the devclass field (when it arrives), so it may obtain +the proper linkage internally. It should also initialize as many of +the callbacks as possible, though each is optional. + +Declaration +~~~~~~~~~~~ + +As stated above, struct device_driver objects are statically +allocated. Below is an example declaration of the eepro100 +driver. This declaration is hypothetical only; it relies on the driver +being converted completely to the new model:: + + static struct device_driver eepro100_driver = { + .name = "eepro100", + .bus = &pci_bus_type, + + .probe = eepro100_probe, + .remove = eepro100_remove, + .suspend = eepro100_suspend, + .resume = eepro100_resume, + }; + +Most drivers will not be able to be converted completely to the new +model because the bus they belong to has a bus-specific structure with +bus-specific fields that cannot be generalized. + +The most common example of this are device ID structures. A driver +typically defines an array of device IDs that it supports. The format +of these structures and the semantics for comparing device IDs are +completely bus-specific. Defining them as bus-specific entities would +sacrifice type-safety, so we keep bus-specific structures around. + +Bus-specific drivers should include a generic struct device_driver in +the definition of the bus-specific driver. Like this:: + + struct pci_driver { + const struct pci_device_id *id_table; + struct device_driver driver; + }; + +A definition that included bus-specific fields would look like +(using the eepro100 driver again):: + + static struct pci_driver eepro100_driver = { + .id_table = eepro100_pci_tbl, + .driver = { + .name = "eepro100", + .bus = &pci_bus_type, + .probe = eepro100_probe, + .remove = eepro100_remove, + .suspend = eepro100_suspend, + .resume = eepro100_resume, + }, + }; + +Some may find the syntax of embedded struct initialization awkward or +even a bit ugly. So far, it's the best way we've found to do what we want... + +Registration +~~~~~~~~~~~~ + +:: + + int driver_register(struct device_driver *drv); + +The driver registers the structure on startup. For drivers that have +no bus-specific fields (i.e. don't have a bus-specific driver +structure), they would use driver_register and pass a pointer to their +struct device_driver object. + +Most drivers, however, will have a bus-specific structure and will +need to register with the bus using something like pci_driver_register. + +It is important that drivers register their driver structure as early as +possible. Registration with the core initializes several fields in the +struct device_driver object, including the reference count and the +lock. These fields are assumed to be valid at all times and may be +used by the device model core or the bus driver. + + +Transition Bus Drivers +~~~~~~~~~~~~~~~~~~~~~~ + +By defining wrapper functions, the transition to the new model can be +made easier. Drivers can ignore the generic structure altogether and +let the bus wrapper fill in the fields. For the callbacks, the bus can +define generic callbacks that forward the call to the bus-specific +callbacks of the drivers. + +This solution is intended to be only temporary. In order to get class +information in the driver, the drivers must be modified anyway. Since +converting drivers to the new model should reduce some infrastructural +complexity and code size, it is recommended that they are converted as +class information is added. + +Access +~~~~~~ + +Once the object has been registered, it may access the common fields of +the object, like the lock and the list of devices:: + + int driver_for_each_dev(struct device_driver *drv, void *data, + int (*callback)(struct device *dev, void *data)); + +The devices field is a list of all the devices that have been bound to +the driver. The LDM core provides a helper function to operate on all +the devices a driver controls. This helper locks the driver on each +node access, and does proper reference counting on each device as it +accesses it. + + +sysfs +~~~~~ + +When a driver is registered, a sysfs directory is created in its +bus's directory. In this directory, the driver can export an interface +to userspace to control operation of the driver on a global basis; +e.g. toggling debugging output in the driver. + +A future feature of this directory will be a 'devices' directory. This +directory will contain symlinks to the directories of devices it +supports. + + + +Callbacks +~~~~~~~~~ + +:: + + int (*probe) (struct device *dev); + +The probe() entry is called in task context, with the bus's rwsem locked +and the driver partially bound to the device. Drivers commonly use +container_of() to convert "dev" to a bus-specific type, both in probe() +and other routines. That type often provides device resource data, such +as pci_dev.resource[] or platform_device.resources, which is used in +addition to dev->platform_data to initialize the driver. + +This callback holds the driver-specific logic to bind the driver to a +given device. That includes verifying that the device is present, that +it's a version the driver can handle, that driver data structures can +be allocated and initialized, and that any hardware can be initialized. +Drivers often store a pointer to their state with dev_set_drvdata(). +When the driver has successfully bound itself to that device, then probe() +returns zero and the driver model code will finish its part of binding +the driver to that device. + +A driver's probe() may return a negative errno value to indicate that +the driver did not bind to this device, in which case it should have +released all resources it allocated. + +Optionally, probe() may return -EPROBE_DEFER if the driver depends on +resources that are not yet available (e.g., supplied by a driver that +hasn't initialized yet). The driver core will put the device onto the +deferred probe list and will try to call it again later. If a driver +must defer, it should return -EPROBE_DEFER as early as possible to +reduce the amount of time spent on setup work that will need to be +unwound and reexecuted at a later time. + +.. warning:: + -EPROBE_DEFER must not be returned if probe() has already created + child devices, even if those child devices are removed again + in a cleanup path. If -EPROBE_DEFER is returned after a child + device has been registered, it may result in an infinite loop of + .probe() calls to the same driver. + +:: + + void (*sync_state) (struct device *dev); + +sync_state is called only once for a device. It's called when all the consumer +devices of the device have successfully probed. The list of consumers of the +device is obtained by looking at the device links connecting that device to its +consumer devices. + +The first attempt to call sync_state() is made during late_initcall_sync() to +give firmware and drivers time to link devices to each other. During the first +attempt at calling sync_state(), if all the consumers of the device at that +point in time have already probed successfully, sync_state() is called right +away. If there are no consumers of the device during the first attempt, that +too is considered as "all consumers of the device have probed" and sync_state() +is called right away. + +If during the first attempt at calling sync_state() for a device, there are +still consumers that haven't probed successfully, the sync_state() call is +postponed and reattempted in the future only when one or more consumers of the +device probe successfully. If during the reattempt, the driver core finds that +there are one or more consumers of the device that haven't probed yet, then +sync_state() call is postponed again. + +A typical use case for sync_state() is to have the kernel cleanly take over +management of devices from the bootloader. For example, if a device is left on +and at a particular hardware configuration by the bootloader, the device's +driver might need to keep the device in the boot configuration until all the +consumers of the device have probed. Once all the consumers of the device have +probed, the device's driver can synchronize the hardware state of the device to +match the aggregated software state requested by all the consumers. Hence the +name sync_state(). + +While obvious examples of resources that can benefit from sync_state() include +resources such as regulator, sync_state() can also be useful for complex +resources like IOMMUs. For example, IOMMUs with multiple consumers (devices +whose addresses are remapped by the IOMMU) might need to keep their mappings +fixed at (or additive to) the boot configuration until all its consumers have +probed. + +While the typical use case for sync_state() is to have the kernel cleanly take +over management of devices from the bootloader, the usage of sync_state() is +not restricted to that. Use it whenever it makes sense to take an action after +all the consumers of a device have probed:: + + int (*remove) (struct device *dev); + +remove is called to unbind a driver from a device. This may be +called if a device is physically removed from the system, if the +driver module is being unloaded, during a reboot sequence, or +in other cases. + +It is up to the driver to determine if the device is present or +not. It should free any resources allocated specifically for the +device; i.e. anything in the device's driver_data field. + +If the device is still present, it should quiesce the device and place +it into a supported low-power state. + +:: + + int (*suspend) (struct device *dev, pm_message_t state); + +suspend is called to put the device in a low power state. + +:: + + int (*resume) (struct device *dev); + +Resume is used to bring a device back from a low power state. + + +Attributes +~~~~~~~~~~ + +:: + + struct driver_attribute { + struct attribute attr; + ssize_t (*show)(struct device_driver *driver, char *buf); + ssize_t (*store)(struct device_driver *, const char *buf, size_t count); + }; + +Device drivers can export attributes via their sysfs directories. +Drivers can declare attributes using a DRIVER_ATTR_RW and DRIVER_ATTR_RO +macro that works identically to the DEVICE_ATTR_RW and DEVICE_ATTR_RO +macros. + +Example:: + + DRIVER_ATTR_RW(debug); + +This is equivalent to declaring:: + + struct driver_attribute driver_attr_debug; + +This can then be used to add and remove the attribute from the +driver's directory using:: + + int driver_create_file(struct device_driver *, const struct driver_attribute *); + void driver_remove_file(struct device_driver *, const struct driver_attribute *); |