[PATCH] bootstd: Allow PXE boot to be disabled

[Tony Dinh]

Hi Tom,

On Fri, Oct 10, 2025 at 1:07 PM Tom Rini <trini at konsulko.com> wrote:
>
> On Fri, Oct 10, 2025 at 12:38:58PM -0700, Tony Dinh wrote:
> > Hi Tom & Simon,
> >
> > On Fri, Oct 10, 2025 at 7:28 AM Tom Rini <trini at konsulko.com> wrote:
> > >
> > > On Thu, Oct 09, 2025 at 10:29:17PM -0700, Tony Dinh wrote:
> > >
> > > > Make it possible to disable CMD_PXE.
> > > > Remove unnecessary PXE_UTILS selection in BOOTMETH_EXTLINUX config.
> > > > In extlinux_boot(), invoke pxe utils only when
> > > > CONFIG_BOOTMETH_EXTLINUX_PXE is enabled.
> > > >
> > > > This patch results in about 9K reduction in image size when
> > > > PXE boot is disabled.
> > > >
> > > > Signed-off-by: Tony Dinh <mibodhi at gmail.com>
> > > > ---
> > > >
> > > >  boot/Kconfig             |  3 +--
> > > >  boot/bootmeth_extlinux.c | 18 ++++++++++--------
> > > >  2 files changed, 11 insertions(+), 10 deletions(-)
> > >
> > > Is some part of the symbol logic here wrong? A challenge is that "PXE"
> > > is also where the logic to parse extlinux.conf style files came from,
> > > and I thought we had split those two out. And then there's this:
> > >
> > > >
> > > > diff --git a/boot/Kconfig b/boot/Kconfig
> > > > index 2993cd7f9ba..403ce4c3d46 100644
> > > > --- a/boot/Kconfig
> > > > +++ b/boot/Kconfig
> > > > @@ -421,10 +421,10 @@ config BOOT_DEFAULTS_CMDS
> > > >       select CMD_PART if PARTITIONS
> > > >       select CMD_DHCP if CMD_NET
> > > >       select CMD_PING if CMD_NET
> > > > -     select CMD_PXE if CMD_NET
> > > >       select CMD_BOOTI if ARM64
> > > >       select CMD_BOOTZ if ARM && !ARM64
> > > >       imply CMD_MII if NET
> > > > +     imply CMD_PXE if CMD_NET
> > >
> > > This is one of the things where defaults isn't supposed to be so easy to
> > > get out of. How many platforms are you wanting to then disable CMD_PXE
> > > on to save space?
> >
> > I'm simply trying to compile out PXE for a board that I'm working on!
> > The only thing I need is booting with scripts on a block device. And
> > it looks like we have to include everything in bootstd to use it. It
> > seems wrong to make the image a lot larger than needed for boards that
> > never use a specific feature.
> >
> > I would agree about  "defaults isn't supposed to be so easy to get out
> > of". But in this case (and similarly in other CMD_x), CMD_PXE brings
> > in all dependencies for PXE including pxe_utils.
>
> So, as a preface, it's quite likely that we do need to tweak some of the
> Kconfig logic here. To help better understand the use case:
> - Does this platform have networking devices in U-Boot?
> - Are you wanting to support arbitrary off the shelf OS distributions?

Yes to both. Networking is enabled in U-Boot, but not used for
booting. And it should boot various off-the-shell OS. U-Boot is on a
512KB partition on SPI flash (why I want to keep u-boot image as small
as possible).

Thanks for your reply!
Tony

> Because if you don't have networking at all, then we should indeed be
> able to bring the library part of PXE (parse extlinux.conf style files)
> without bringing in all of PXE.
>
> If you don't want to allow arbitrary OS distributions then it should be
> possible to turn off the CONFIG that brings in everything an arbitrary
> OS might want (for example, install via network) and still have
> standard boot available for block devices and scripts and extlinux
> support.
>
> --
> Tom