[PATCH v2] cmd: pxe: add alias devicetree-overlay for fdtoverlays

[Ramon Fried]

On Wed, Sep 21, 2022 at 4:27 PM Edoardo Tomelleri <e.tomell at 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 at 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.
> --
> 2.37.3
>
Reviewed-by: Ramon Fried <rfried.dev at gmail.com>