mbox series

[Concept,v2,00/15] boot: Support priority for global bootmeths

Message ID 20250930232611.1564850-1-sjg@u-boot.org
Headers
Series boot: Support priority for global bootmeths |

Message

Simon Glass Sept. 30, 2025, 11:25 p.m. UTC 
  From: Simon Glass <sjg@chromium.org>

At present global bootmeths always run first, before all other
bootmeths. Optimisations in the code take advantage of this, putting
them at the end, so they can be used once and then forgotten.

In some cases it is useful to run global bootmeths later in the boot.
For example, the EFI-bootmgr bootmeth may itself scan devices and the
network, so running it first can hold up the boot significantly for
boards not actually relying on EFI-bootmgr to boot.

This series introduces a new field in global bootmeths which indicates
the priority, using the same scheme as is used with bootdev hunters.
Thus it is possible to insert the EFI-bootmgr bootmeth just before the
hunter for network bootdevs is invoked.

Despite the simplicity of the concept and the relatively small series,
this is a fairly significant enhancement. It is also quite tricky to
implement, largely due to the way the original code was written, with
global bootmeths being a small, size-optimised add-on to the original
bootstd implementation.

For now we only allow each global bootmeth to run at most once, but this
implementation is written in a way that we could relax that if needed.
Then the bootmeth itself could decide whether to run at any particular
point in the bootflow iteration.

Size growth is about 390 bytes on Thumb2 (e.g. firefly-rk3288) if
CONFIG_BOOTMETH_GLOBAL is enabled, which it normally is. With that
disabled (which saves about 4K on the same platform), there is no
growth.

Changes in v2:
- Add a log_err() for an invalid state
- Update commit message to indicate the bootmeth will always run
- Document how the priority was chosen
- Add a bit more detail suggested by Heinrich

Simon Glass (15):
  boot: Improve comments related to global bootmeths
  boot: Add more debugging to iter_incr()
  boot: Move showing of bootflows out of the command
  boot: Add a new test for global bootmeths
  boot: Update first_glob_method when dropping a bootmeth
  boot: Add a flag for whether there are global bootmeths
  boot: Keep track of which bootmeths have been used
  boot: Move preparing bootdev into a function
  boot: Support rescanning the global bootmeths
  boot: Only run global bootmeths once each
  boot: Implement a priority for global bootmeths
  boot: Don't change the method count after global bootmeths
  boot: Run global bootmeths after all bootdevs are exhausted
  boot: Run the EFI bootmgr just before network devices
  boot: doc: Update for new global-bootmeth features

 boot/bootflow.c                  | 277 +++++++++++++++++++++++++++++--
 boot/bootmeth-uclass.c           |  15 +-
 boot/bootmeth_efi_mgr.c          |   9 +
 cmd/bootflow.c                   |  68 +-------
 doc/develop/bootstd/overview.rst |  40 ++++-
 include/bootflow.h               |  29 +++-
 include/bootmeth.h               |   4 +
 test/boot/bootflow.c             |  73 +++++++-
 8 files changed, 419 insertions(+), 96 deletions(-)