Re: setting PcdPlatformBootTimeOut in PlatformBootManagerLib

["Laszlo Ersek" <lersek@redhat.com>]

On 03/02/20 10:43, Ard Biesheuvel wrote:
> 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?

Just call gRT->SetVariable().

Thanks
Laszlo