This adds keyword devicetree-overlay as an alias for fdtoverlays in
extlinux (sysboot) and pxe to better follow the Boot Loader Specification
[1], improves documentation around them by adding an example for both
fdtoverlays and devicetree-overlay and the environment variable required
for this feature. The link for the spec is updated to the current one.
[1] https://systemd.io/BOOT_LOADER_SPECIFICATION/
Signed-off-by: Edoardo Tomelleri <e.tom...@gmail.com>
---
Changes in v2:
- Updated link to Boot Loader Specification
- Added link to Boot Loader Specification to the patch commit
- Changed README.pxe reusing the same wording as of the aliased commands
boot/pxe_utils.c | 2 ++
doc/README.pxe | 12 ++++++++++++
doc/develop/distro.rst | 32 +++++++++++++++++++++++++++++---
3 files changed, 43 insertions(+), 3 deletions(-)
diff --git a/boot/pxe_utils.c b/boot/pxe_utils.c
index a364fa8bb5..d5c215ae2c 100644
--- a/boot/pxe_utils.c
+++ b/boot/pxe_utils.c
@@ -380,6 +380,7 @@ err:
/**
* label_boot_fdtoverlay() - Loads fdt overlays specified in 'fdtoverlays'
+ * or 'devicetree-overlay'
*
* @ctx: PXE context
* @label: Label to process
@@ -809,6 +810,7 @@ static const struct token keywords[] = {
{"devicetreedir", T_FDTDIR},
{"fdtdir", T_FDTDIR},
{"fdtoverlays", T_FDTOVERLAYS},
+ {"devicetree-overlay", T_FDTOVERLAYS},
{"ontimeout", T_ONTIMEOUT,},
{"ipappend", T_IPAPPEND,},
{"background", T_BACKGROUND,},
diff --git a/doc/README.pxe b/doc/README.pxe
index 75caa01c4a..d14d2bdcc9 100644
--- a/doc/README.pxe
+++ b/doc/README.pxe
@@ -163,6 +163,13 @@ fdtoverlays <path> [...] - if this label is chosen, use
tftp to retrieve the DT
and then applied in the load order to the fdt blob
stored at the
address indicated in the fdt_addr_r environment
variable.
+devicetree-overlay <path> [...] - if this label is chosen, use tftp to retrieve the DT
+ overlay(s) at <path>. it will be temporarily stored at
the
+ address indicated in the fdtoverlay_addr_r environment
variable,
+ and then applied in the load order to the fdt blob
stored at the
+ address indicated in the fdt_addr_r environment variable.
+ Alias for fdtoverlays.
+
kaslrseed - set this label to request random number from hwrng as
kaslr seed.
append <string> - use <string> as the kernel command line when booting this
@@ -178,6 +185,11 @@ fdt <path> - if this label is chosen, use tftp to
retrieve the fdt blob
the fdt_addr_r environment variable, and that address will
be passed to bootm.
+devicetree <path> - if this label is chosen, use tftp to retrieve the fdt blob
+ at <path>. it will be stored at the address indicated in
+ the fdt_addr_r environment variable, and that address will
+ be passed to bootm. Alias for fdt.
+
fdtdir <path> - if this label is chosen, use tftp to retrieve a fdt blob
relative to <path>. If the fdtfile environment variable
is set, <path>/<fdtfile> is retrieved. Otherwise, the
diff --git a/doc/develop/distro.rst b/doc/develop/distro.rst
index 3ee3dac6a2..bc72aa951e 100644
--- a/doc/develop/distro.rst
+++ b/doc/develop/distro.rst
@@ -68,10 +68,10 @@ Boot Configuration Files
The standard format for boot configuration files is that of extlinux.conf, as
handled by U-Boot's "syslinux" (disk) or "pxe boot" (network). This is roughly
-as specified at BootLoaderSpec_:
+as specified at `Boot Loader Specification`_:
-... with the exceptions that the BootLoaderSpec document:
+... with the exceptions that the Boot Loader Specification document:
* Prescribes a separate configuration per boot menu option, whereas U-Boot
lumps all options into a single extlinux.conf file. Hence, U-Boot searches
@@ -81,6 +81,8 @@ as specified at BootLoaderSpec_:
* Does not document the fdtdir option, which automatically selects the DTB to
pass to the kernel.
+See also doc/README.pxe under 'pxe file format'.
+
One example extlinux.conf generated by the Fedora installer is::
# extlinux.conf generated by anaconda
@@ -115,6 +117,25 @@ One example extlinux.conf generated by the Fedora
installer is::
fdtdir /boot/dtb-3.16.0-0.rc6.git1.1.fc22.armv7hl+lpae
+One example of hand-crafted extlinux.conf::
+
+ menu title Select kernel
+ timeout 100
+
+ label Arch with uart devicetree overlay
+ kernel /arch/Image.gz
+ initrd /arch/initramfs-linux.img
+ fdt /dtbs/arch/board.dtb
+ fdtoverlays /dtbs/arch/overlay/uart0-gpio0-1.dtbo
+ append console=ttyS0,115200 console=tty1 rw
root=UUID=fc0d0284-ca84-4194-bf8a-4b9da8d66908
+
+ label Arch with uart devicetree overlay but with Boot Loader Specification
keys
+ kernel /arch/Image.gz
+ initrd /arch/initramfs-linux.img
+ devicetree /dtbs/arch/board.dtb
+ devicetree-overlay /dtbs/arch/overlay/uart0-gpio0-1.dtbo
+ append console=ttyS0,115200 console=tty1 rw
root=UUID=fc0d0284-ca84-4194-bf8a-4b9da8d66908
+
Another hand-crafted network boot configuration file is::
TIMEOUT 100
@@ -214,6 +235,11 @@ fdt_addr_r:
A size of 1MB for the FDT/DTB seems reasonable.
+fdtoverlay_addr_r:
+ Mandatory. The location in RAM where DTB overlays will be temporarily
+ stored and then applied in the load order to the fdt blob stored at the
+ address indicated in the fdt_addr_r environment variable.
+
fdtfile:
Mandatory. the name of the DTB file for the specific board for instance
the espressobin v5 board the value is "marvell/armada-3720-espressobin.dtb"
@@ -408,7 +434,7 @@ way in future u-boot versions. In particular the <device
type>_boot
variables (e.g. mmc_boot, usb_boot) are a strictly internal implementation
detail and must not be used as a public interface.
-.. _BootLoaderSpec: http://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/
+.. _`Boot Loader Specification`: https://systemd.io/BOOT_LOADER_SPECIFICATION/
.. sectionauthor:: (C) Copyright 2014 Red Hat Inc.
.. sectionauthor:: Copyright (c) 2014-2015, NVIDIA CORPORATION. All rights
reserved.
