diff options
author | Linus Torvalds | 2016-03-17 13:38:00 -0700 |
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committer | Linus Torvalds | 2016-03-17 13:38:00 -0700 |
commit | 1a4ab084afaa8e5405a3e22aca21478ee3ca5d59 (patch) | |
tree | fe559fa3377199d335ab477e86050f34d76c13f0 /Documentation/devicetree | |
parent | 45cb5230f862d10209b83e488b20916555d70c55 (diff) | |
parent | 112d125a89479519efc437b2961b8d4a98761c1b (diff) |
Merge tag 'driver-core-4.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
Pull driver core updates from Greg KH:
"Just a few patches this time around for the 4.6-rc1 merge window.
Largest is a new firmware driver, but there are some other updates to
the driver core in here as well, the shortlog has the details.
All have been in linux-next for a while with no reported issues"
* tag 'driver-core-4.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
Revert "driver-core: platform: probe of-devices only using list of compatibles"
firmware: qemu config needs I/O ports
firmware: qemu_fw_cfg.c: fix typo FW_CFG_DATA_OFF
driver-core: platform: probe of-devices only using list of compatibles
driver-core: platform: fix typo in documentation for multi-driver helper
component: remove impossible condition
drivers: dma-coherent: simplify dma_init_coherent_memory return value
devicetree: update documentation for fw_cfg ARM bindings
firmware: create directory hierarchy for sysfs fw_cfg entries
firmware: introduce sysfs driver for QEMU's fw_cfg device
kobject: export kset_find_obj() for module use
driver core: bus: use to_subsys_private and to_device_private_bus
driver core: bus: use list_for_each_entry*
debugfs: Add stub function for debugfs_create_automount().
kernfs: make kernfs_walk_ns() use kernfs_pr_cont_buf[]
Diffstat (limited to 'Documentation/devicetree')
-rw-r--r-- | Documentation/devicetree/bindings/arm/fw-cfg.txt | 38 |
1 files changed, 2 insertions, 36 deletions
diff --git a/Documentation/devicetree/bindings/arm/fw-cfg.txt b/Documentation/devicetree/bindings/arm/fw-cfg.txt index 953fb640d9c4..fd54e1db2156 100644 --- a/Documentation/devicetree/bindings/arm/fw-cfg.txt +++ b/Documentation/devicetree/bindings/arm/fw-cfg.txt @@ -11,43 +11,9 @@ QEMU exposes the control and data register to ARM guests as memory mapped registers; their location is communicated to the guest's UEFI firmware in the DTB that QEMU places at the bottom of the guest's DRAM. -The guest writes a selector value (a key) to the selector register, and then -can read the corresponding data (produced by QEMU) via the data register. If -the selected entry is writable, the guest can rewrite it through the data -register. +The authoritative guest-side hardware interface documentation to the fw_cfg +device can be found in "docs/specs/fw_cfg.txt" in the QEMU source tree. -The selector register takes keys in big endian byte order. - -The data register allows accesses with 8, 16, 32 and 64-bit width (only at -offset 0 of the register). Accesses larger than a byte are interpreted as -arrays, bundled together only for better performance. The bytes constituting -such a word, in increasing address order, correspond to the bytes that would -have been transferred by byte-wide accesses in chronological order. - -The interface allows guest firmware to download various parameters and blobs -that affect how the firmware works and what tables it installs for the guest -OS. For example, boot order of devices, ACPI tables, SMBIOS tables, kernel and -initrd images for direct kernel booting, virtual machine UUID, SMP information, -virtual NUMA topology, and so on. - -The authoritative registry of the valid selector values and their meanings is -the QEMU source code; the structure of the data blobs corresponding to the -individual key values is also defined in the QEMU source code. - -The presence of the registers can be verified by selecting the "signature" blob -with key 0x0000, and reading four bytes from the data register. The returned -signature is "QEMU". - -The outermost protocol (involving the write / read sequences of the control and -data registers) is expected to be versioned, and/or described by feature bits. -The interface revision / feature bitmap can be retrieved with key 0x0001. The -blob to be read from the data register has size 4, and it is to be interpreted -as a uint32_t value in little endian byte order. The current value -(corresponding to the above outer protocol) is zero. - -The guest kernel is not expected to use these registers (although it is -certainly allowed to); the device tree bindings are documented here because -this is where device tree bindings reside in general. Required properties: |