On Wed, Sep 21, 2022 at 4:27 PM Edoardo Tomelleri e.tomell@gmail.com wrote:
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.tomell@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 theaddress indicated in the fdtoverlay_addr_r environment variable,and then applied in the load order to the fdt blob stored at theaddress 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 inthe fdt_addr_r environment variable, and that address willbe 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.gzinitrd /arch/initramfs-linux.imgfdt /dtbs/arch/board.dtbfdtoverlays /dtbs/arch/overlay/uart0-gpio0-1.dtboappend 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.gzinitrd /arch/initramfs-linux.imgdevicetree /dtbs/arch/board.dtbdevicetree-overlay /dtbs/arch/overlay/uart0-gpio0-1.dtboappend console=ttyS0,115200 console=tty1 rw root=UUID=fc0d0284-ca84-4194-bf8a-4b9da8d66908Another 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. -- 2.37.3
Reviewed-by: Ramon Fried rfried.dev@gmail.com