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Message-Id: <1449242946-12062-5-git-send-email-somlo@cmu.edu> Date: Fri, 4 Dec 2015 10:29:06 -0500 From: "Gabriel L. Somlo" <somlo@....edu> To: gregkh@...uxfoundation.org, robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com, ijc+devicetree@...lion.org.uk, galak@...eaurora.org, arnd@...db.de, lersek@...hat.com, ralf@...ux-mips.org, rmk+kernel@....linux.org.uk, eric@...olt.net, hanjun.guo@...aro.org, zajec5@...il.com, sudeep.holla@....com, agross@...eaurora.org, linux-api@...r.kernel.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org Cc: qemu-devel@...gnu.org, jordan.l.justen@...el.com, mst@...hat.com, peter.maydell@...aro.org, leif.lindholm@...aro.org, ard.biesheuvel@...aro.org, pbonzini@...hat.com, kraxel@...hat.com, luto@...capital.net, stefanha@...il.com, revol@...e.fr, matt@...eblueprint.co.uk Subject: [PATCH v6 4/4] devicetree: update documentation for fw_cfg ARM bindings From: Gabriel Somlo <somlo@....edu> Remove fw_cfg hardware interface details from Documentation/devicetree/bindings/arm/fw-cfg.txt, and replace them with a pointer to the authoritative documentation in the QEMU source tree. Signed-off-by: Gabriel Somlo <somlo@....edu> Cc: Laszlo Ersek <lersek@...hat.com> Acked-by: Rob Herring <robh@...nel.org> Reviewed-by: Laszlo Ersek <lersek@...hat.com> --- Documentation/devicetree/bindings/arm/fw-cfg.txt | 38 ++---------------------- 1 file changed, 2 insertions(+), 36 deletions(-) diff --git a/Documentation/devicetree/bindings/arm/fw-cfg.txt b/Documentation/devicetree/bindings/arm/fw-cfg.txt index 953fb64..fd54e1d 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: -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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