Re: setting PcdPlatformBootTimeOut in PlatformBootManagerLib

["Ard Biesheuvel" <ard.biesheuvel@linaro.org>]

On Mon, 2 Mar 2020 at 10:40, Laszlo Ersek <lersek@redhat.com> wrote:
>
> On 03/02/20 00:13, Laszlo Ersek wrote:
> > Hi Ray,
> >
> > OvmfPkg and ArmVirtPkg platforms set PcdPlatformBootTimeOut in their
> > PlatformBootManagerLib instances, in BeforeConsole(). This generally
> > works, except for one aspect: in BdsEntry(), the Timeout UEFI variable
> > is set from the PCD before BeforeConsole() is called.
> >
> > The Timeout variable is in this case purely informative, but I'd still
> > like it to reflect the PCD's value. Given that I'd like to keep the
> > subject PcdSet16S() call in PlatformBootManagerLib, I see two options:
> >
> > (1) Modify BdsEntry(): re-check the value of the PCD a bit before
> > BdsWait() -- when the PCD is really needed --, and if it has changed
> > relative to the first seen value, store the new PCD value to the UEFI
> > variable *again*.
> >
> > This would keep platforms happy that expect Timeout to already carry the
> > PCDs value upon entering BeforeConsole(), and it would allow platforms
> > to re-set the PCD (and Timeout too) in either BeforeConsole() or
> > AfterConsole().
> >
> > (2) Alternatively, add a CONSTRUCTOR function to the
> > PlatformBootManagerLib instances for setting the PCD before BdsEntry()
> > is invoked at all. I'm a bit concerned about this, as we'd have to
> > ensure that *all* the lib instances that participate in this PCD setting
> > (including the lib instances that let us calculate the value) have
> > CONSTRUCTOR functions (otherwise the topological sorting of CONSTRUCTOR
> > calls is not complete).
>
> (3) We could also just rewrite Timeout ourselves, in
> PlatformBootManagerLib, where we set the PCD.
>

'Rewrite' as in access the global variable? Or access the HII guts of
the 'timeout' entry in the menus?