Merge tag 'docs-5.4' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "It's a somewhat calmer cycle for docs this time, as the churn of the
  mass RST conversion is happily mostly behind us.

   - A new document on reproducible builds.

   - We finally got around to zapping the documentation for hardware
     support that was removed in 2004; one doesn't want to rush these
     things.

   - The usual assortment of fixes, typo corrections, etc"

* tag 'docs-5.4' of git://git.lwn.net/linux: (67 commits)
  Documentation: kbuild: Add document about reproducible builds
  docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi]
  Documentation: Add "earlycon=sbi" to the admin guide
  doc:lock: remove reference to clever use of read-write lock
  devices.txt: improve entry for comedi (char major 98)
  docs: mtd: Update spi nor reference driver
  doc: arm64: fix grammar dtb placed in no attributes region
  Documentation: sysrq: don't recommend 'S' 'U' before 'B'
  mailmap: Update email address for Quentin Perret
  docs: ftrace: clarify when tracing is disabled by the trace file
  docs: process: fix broken link
  Documentation/arm/samsung-s3c24xx: Remove stray U+FEFF character to fix title
  Documentation/arm/sa1100/assabet: Fix 'make assabet_defconfig' command
  Documentation/arm/sa1100: Remove some obsolete documentation
  docs/zh_CN: update Chinese howto.rst for latexdocs making
  Documentation: virt: Fix broken reference to virt tree's index
  docs: Fix typo on pull requests guide
  kernel-doc: Allow anonymous enum
  Documentation: sphinx: Don't parse socket() as identifier reference
  Documentation: sphinx: Add missing comma to list of strings
  ...

1 files changed, 62 insertions, 0 deletions

diff --git a/Documentation/riscv/boot-image-header.rst b/Documentation/riscv/boot-image-header.rst
new file mode 100644
index 000000000000..7b4d1d747585
--- /dev/null
+++ b/Documentation/riscv/boot-image-header.rst
@@ -0,0 +1,62 @@
+=================================
+Boot image header in RISC-V Linux
+=================================
+
+:Author: Atish Patra <atish.patra@wdc.com>
+:Date:   20 May 2019
+
+This document only describes the boot image header details for RISC-V Linux.
+
+TODO:
+  Write a complete booting guide.
+
+The following 64-byte header is present in decompressed Linux kernel image::
+
+	u32 code0;		  /* Executable code */
+	u32 code1;		  /* Executable code */
+	u64 text_offset;	  /* Image load offset, little endian */
+	u64 image_size;		  /* Effective Image size, little endian */
+	u64 flags;		  /* kernel flags, little endian */
+	u32 version;		  /* Version of this header */
+	u32 res1 = 0;		  /* Reserved */
+	u64 res2 = 0;		  /* Reserved */
+	u64 magic = 0x5643534952; /* Magic number, little endian, "RISCV" */
+	u32 magic2 = 0x56534905;  /* Magic number 2, little endian, "RSC\x05" */
+	u32 res4;		  /* Reserved for PE COFF offset */
+
+This header format is compliant with PE/COFF header and largely inspired from
+ARM64 header. Thus, both ARM64 & RISC-V header can be combined into one common
+header in future.
+
+Notes
+=====
+
+- This header can also be reused to support EFI stub for RISC-V in future. EFI
+  specification needs PE/COFF image header in the beginning of the kernel image
+  in order to load it as an EFI application. In order to support EFI stub,
+  code0 should be replaced with "MZ" magic string and res5(at offset 0x3c) should
+  point to the rest of the PE/COFF header.
+
+- version field indicate header version number
+
+	==========  =============
+	Bits 0:15   Minor version
+	Bits 16:31  Major version
+	==========  =============
+
+  This preserves compatibility across newer and older version of the header.
+  The current version is defined as 0.2.
+
+- The "magic" field is deprecated as of version 0.2.  In a future
+  release, it may be removed.  This originally should have matched up
+  with the ARM64 header "magic" field, but unfortunately does not.
+  The "magic2" field replaces it, matching up with the ARM64 header.
+
+- In current header, the flags field has only one field.
+
+	=====  ====================================
+	Bit 0  Kernel endianness. 1 if BE, 0 if LE.
+	=====  ====================================
+
+- Image size is mandatory for boot loader to load kernel image. Booting will
+  fail otherwise.