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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-23 13:28:57 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-23 13:28:57 -0700 |
| commit | 4352b8aee98005853aa63f57d6377282de17a33f (patch) | |
| tree | 27614d7a9ef05c32d089004e104364ce42324837 /Documentation/admin-guide/device-mapper/dm-init.rst | |
| download | linux-stable-4352b8aee98005853aa63f57d6377282de17a33f.tar.gz linux-stable-4352b8aee98005853aa63f57d6377282de17a33f.zip | |
Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted
Pull I3C updates from Alexandre Belloni:
"A new driver this cycle, for the AMD AXI I3C controller.
There are also new features such as IBI wakeup support, SETAASA device
discovery and ACPI support for the the DAA methods, meaning we can now
communicate with the SPD devices on DDR5 modules.
New driver:
- AMD AXI I3C master controller
Subsystem:
- I3C Common Command Code (CCC) handling improvements, especially
around GET CCCs
- SETAASA device discovery support
- ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
well as I2C devices on I3C bus
- IBI-based wakeup support
Drivers:
- dw: SETAASA support
- mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
controller support, PIO queue management support for HCI v1.2
- renesas: improve suspend to RAM support, add runtime PM support"
* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
i3c: dw: reduce do_daa time if there's no client
i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
i3c: dw: rename "pclk" to "apb" to match dt-binding
i3c: dw: make struct dw_i3c_cmd smaller
i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
i3c: renesas: Don't register devices when ENTDAA times out
i3c: master: dw-i3c-master: fix OD timing for first broadcast
i3c: mipi-i3c-hci: Advertise IBI wakeup capability
i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
i3c: master: Reject IBI requests from non-IBI-capable devices
i3c: master: Add helper to query bus wakeup requirements
i3c: master: Report wakeup events for IBIs
i3c: master: Support IBI-based wakeup capability
i3c: master: Fix potential UAF in i3c_device_match()
i3c: master: Fix potential UAF in i3c_device_uevent()
i3c: Make dev->desc locking assumptions explicit
i3c: master: Fix use-after-free of master->this
...
Diffstat (limited to 'Documentation/admin-guide/device-mapper/dm-init.rst')
| -rw-r--r-- | Documentation/admin-guide/device-mapper/dm-init.rst | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/Documentation/admin-guide/device-mapper/dm-init.rst b/Documentation/admin-guide/device-mapper/dm-init.rst new file mode 100644 index 000000000..981d6a907 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-init.rst @@ -0,0 +1,133 @@ +================================ +Early creation of mapped devices +================================ + +It is possible to configure a device-mapper device to act as the root device for +your system in two ways. + +The first is to build an initial ramdisk which boots to a minimal userspace +which configures the device, then pivot_root(8) in to it. + +The second is to create one or more device-mappers using the module parameter +"dm-mod.create=" through the kernel boot command line argument. + +The format is specified as a string of data separated by commas and optionally +semi-colons, where: + + - a comma is used to separate fields like name, uuid, flags and table + (specifies one device) + - a semi-colon is used to separate devices. + +So the format will look like this:: + + dm-mod.create=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<name>,<uuid>,<minor>,<flags>,<table>[,<table>+]+] + +Where:: + + <name> ::= The device name. + <uuid> ::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | "" + <minor> ::= The device minor number | "" + <flags> ::= "ro" | "rw" + <table> ::= <start_sector> <num_sectors> <target_type> <target_args> + <target_type> ::= "verity" | "linear" | ... (see list below) + +The dm line should be equivalent to the one used by the dmsetup tool with the +`--concise` argument. + +Target types +============ + +Not all target types are available as there are serious risks in allowing +activation of certain DM targets without first using userspace tools to check +the validity of associated metadata. + +======================= ======================================================= +`cache` constrained, userspace should verify cache device +`crypt` allowed +`delay` allowed +`era` constrained, userspace should verify metadata device +`flakey` constrained, meant for test +`linear` allowed +`log-writes` constrained, userspace should verify metadata device +`mirror` constrained, userspace should verify main/mirror device +`raid` constrained, userspace should verify metadata device +`snapshot` constrained, userspace should verify src/dst device +`snapshot-origin` allowed +`snapshot-merge` constrained, userspace should verify src/dst device +`striped` allowed +`switch` constrained, userspace should verify dev path +`thin` constrained, requires dm target message from userspace +`thin-pool` constrained, requires dm target message from userspace +`verity` allowed +`writecache` constrained, userspace should verify cache device +`zero` constrained, not meant for rootfs +======================= ======================================================= + +If the target is not listed above, it is constrained by default (not tested). + +Examples +======== +An example of booting to a linear array made up of user-mode linux block +devices:: + + dm-mod.create="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0 + +This will boot to a rw dm-linear target of 8192 sectors split across two block +devices identified by their major:minor numbers. After boot, udev will rename +this target to /dev/mapper/lroot (depending on the rules). No uuid was assigned. + +An example of multiple device-mappers, with the dm-mod.create="..." contents +is shown here split on multiple lines for readability:: + + dm-linear,,1,rw, + 0 32768 linear 8:1 0, + 32768 1024000 linear 8:2 0; + dm-verity,,3,ro, + 0 1638400 verity 1 /dev/sdc1 /dev/sdc2 4096 4096 204800 1 sha256 + ac87db56303c9c1da433d7209b5a6ef3e4779df141200cbd7c157dcb8dd89c42 + 5ebfe87f7df3235b80a117ebc4078e44f55045487ad4a96581d1adb564615b51 + +Other examples (per target): + +"crypt":: + + dm-crypt,,8,ro, + 0 1048576 crypt aes-xts-plain64 + babebabebabebabebabebabebabebabebabebabebabebabebabebabebabebabe 0 + /dev/sda 0 1 allow_discards + +"delay":: + + dm-delay,,4,ro,0 409600 delay /dev/sda1 0 500 + +"linear":: + + dm-linear,,,rw, + 0 32768 linear /dev/sda1 0, + 32768 1024000 linear /dev/sda2 0, + 1056768 204800 linear /dev/sda3 0, + 1261568 512000 linear /dev/sda4 0 + +"snapshot-origin":: + + dm-snap-orig,,4,ro,0 409600 snapshot-origin 8:2 + +"striped":: + + dm-striped,,4,ro,0 1638400 striped 4 4096 + /dev/sda1 0 /dev/sda2 0 /dev/sda3 0 /dev/sda4 0 + +"verity":: + + dm-verity,,4,ro, + 0 1638400 verity 1 8:1 8:2 4096 4096 204800 1 sha256 + fb1a5a0f00deb908d8b53cb270858975e76cf64105d412ce764225d53b8f3cfd + 51934789604d1b92399c52e7cb149d1b3a1b74bbbcb103b2a0aaacbed5c08584 + +For setups using device-mapper on top of asynchronously probed block +devices (MMC, USB, ..), it may be necessary to tell dm-init to +explicitly wait for them to become available before setting up the +device-mapper tables. This can be done with the "dm-mod.waitfor=" +module parameter, which takes a list of devices to wait for:: + + dm-mod.waitfor=<device1>[,..,<deviceN>] |
