[PATCH 04/13] doc: Add a description for bootmeth_pxe

[Heinrich Schuchardt]

On 7/15/24 12:13, Simon Glass wrote:
> Add documentation for the pxe bootmeth.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
>   doc/develop/bootstd/index.rst    |  1 +
>   doc/develop/bootstd/overview.rst |  2 +-
>   doc/develop/bootstd/pxelinux.rst | 27 +++++++++++++++++++++++++++
>   3 files changed, 29 insertions(+), 1 deletion(-)
>   create mode 100644 doc/develop/bootstd/pxelinux.rst
>
> diff --git a/doc/develop/bootstd/index.rst b/doc/develop/bootstd/index.rst
> index 5bbb3d633a3..5052afe448f 100644
> --- a/doc/develop/bootstd/index.rst
> +++ b/doc/develop/bootstd/index.rst
> @@ -8,3 +8,4 @@ Standard Boot
>
>      overview
>      extlinux
> +   pxelinux
> diff --git a/doc/develop/bootstd/overview.rst b/doc/develop/bootstd/overview.rst
> index 086a0b1281d..fd0692daf0d 100644
> --- a/doc/develop/bootstd/overview.rst
> +++ b/doc/develop/bootstd/overview.rst
> @@ -413,7 +413,7 @@ Available bootmeth drivers
>   Bootmeth drivers are provided for:
>
>      - :doc:`extlinux / syslinux <extlinux>` boot from a disk
> -   - extlinux boot from a network (PXE)
> +   - :doc:`extlinux / syslinux <extlinux>` boot from a network (PXE)
>      - U-Boot scripts from disk, network or SPI flash
>      - EFI boot using bootefi from disk
>      - VBE
> diff --git a/doc/develop/bootstd/pxelinux.rst b/doc/develop/bootstd/pxelinux.rst
> new file mode 100644
> index 00000000000..08ba67e09c5
> --- /dev/null
> +++ b/doc/develop/bootstd/pxelinux.rst
> @@ -0,0 +1,27 @@
> +.. SPDX-License-Identifier: GPL-2.0+:
> +
> +PXE Bootmeth
> +============
> +
> +PXE (Preboot eXecution-Environment) provides a way to boot an Operating System

%s/Operating System/operating system/

> +over a network interface. The PXE bootmeth supports PXELINUX and allows U-Boot to

%s/bootmeth/boot method/

> +provide a menu of possible Operating Systems from which the user can choose.

PXELINUX is a binary. Does U-Boot really provide a menu when the
PXELINUX binary is downloaded and executed?

> +
> +U-Boot includes a parser for the `extlinux.conf` file described
> +`here <https://uapi-group.org/specifications/specs/boot_loader_specification>`_.
> +It consists primarily of a list of named OSes along with the kernel, initial
> +ramdisk and other settings. The file is retrieved from a network server using
> +tftpboot.

Does this paragraph relate to PXELINUX?

tftpboot is a command and not a protocol. Shouldn't boot methods work
when the command line interface is disabled? I guess you want to replace

%s/tftpboot/the TFTP protocol/

> +
> +When invoked on a bootdev, this bootmeth searches for the file and creates a

%s/bootdev/boot device/
%s/bootmeth/boot method/

> +bootflow if found. See

%s/bootflow/boot flow/

> +`PXELINUX <https://wiki.syslinux.org/wiki/index.php?title=PXELINUX>`_ for
> +a full description of the search procedure.
> +
> +When the bootflow is booted, the bootmeth calls pxe_setup_ctx() to set up the
> +context, then pxe_process() to process the file. Depending on the contents, this
> +may boot an OS or provide a list of options to the user, perhaps with a timeout.
> +
> +The compatible string "u-boot,extlinux-pxe" is used for the driver. The driver
> +is automatically instantiated if there are no bootmeth drivers in the
> +devicetree.

Device-trees contain compatible strings for drivers, not the drivers
themselves.

If every configured boot method is enabled if there is no compatible
string for boot methods in the device-tree, why don't we mention this in
the overview instead of repeating ourselves?

Please, mention the relevant configuration option.

Best regards

Heinrich