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authorLinus Torvalds <torvalds@linux-foundation.org>2016-03-17 13:38:00 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-17 13:38:00 -0700
commit1a4ab084afaa8e5405a3e22aca21478ee3ca5d59 (patch)
treefe559fa3377199d335ab477e86050f34d76c13f0 /Documentation/devicetree
parentMerge tag 'vfio-v4.6-rc1' of git://github.com/awilliam/linux-vfio (diff)
parentRevert "driver-core: platform: probe of-devices only using list of compatibles" (diff)
downloadlinux-dev-1a4ab084afaa8e5405a3e22aca21478ee3ca5d59.tar.xz
linux-dev-1a4ab084afaa8e5405a3e22aca21478ee3ca5d59.zip
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.txt38
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.
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