[PATCH 09/16] efi_loader: imply FAT, FAT_WRITE

[AKASHI Takahiro]

On Tue, Mar 31, 2020 at 10:20:17AM +0200, Mark Kettenis wrote:
> > Date: Tue, 31 Mar 2020 16:44:34 +0900
> > From: AKASHI Takahiro <takahiro.akashi at linaro.org>
> > 
> > On Tue, Mar 31, 2020 at 08:44:02AM +0200, Heinrich Schuchardt wrote:
> > > On  March 31, 2020, 5:28 a.m. UTC Takahiro Akashi wrote:
> > > > On Fri, Mar 27, 2020 at 06:27:53AM +0100, Heinrich Schuchardt wrote:
> > > > > The UEFI spec requires support for the FAT file system.
> > > > >
> > > > > Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
> > > > > ---
> > > > >  lib/efi_loader/Kconfig | 2 ++
> > > > >  1 file changed, 2 insertions(+)
> > > > >
> > > > > diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
> > > > > index 9890144d41..e10ca05549 100644
> > > > > --- a/lib/efi_loader/Kconfig
> > > > > +++ b/lib/efi_loader/Kconfig
> > > > > @@ -15,6 +15,8 @@ config EFI_LOADER
> > > > >  	select HAVE_BLOCK_DEVICE
> > > > >  	select REGEX
> > > > >  	imply CFB_CONSOLE_ANSI
> > > > > +	imply FAT
> > > > > +	imply FAT_WRITE
> > > >
> > > > Obviously, this *imply* doesn't enforce enabling FAT.
> > > > If it is absolutely necessary, another measure should be taken.
> > > 
> > > If somebody wants to minimize the U-Boot size it might be necessary to
> > > do without FAT_WRITE or FAT support.
> > 
> > If so, Get/SetVariable won't be supported even in boot time
> > with your patch applied. It is not practical for almost all users.
> 
> I *strongly* disagree with that statement.  Most users don't care
> about U-Boot providing a full EFI implementation.  They just want to
> boot their OS.  The basic EFI support in U-Boot is good enough for
> that and for OpenBSD and some Linux distros on arm/arm64 this is the
> only bootpath that works.  If adding more code leads to board
> maintainers disabling EFI support this isn't helpful.

Okay, so can you please describe the minimum set of functionality
for you? Without that, the discussion will not be fair.

Anyhow, using "imply" to customize UEFI functionality would be
poor. Instead, we should introduce explicit configuration, say,

config EFI_CUSTOMIZE_RUNTIME_SERVICES

if EFI_CUSTOMIZE_RUNTIME_SERVICES

config EFI_RUNTIME_GET_VARIABLE
   select FAT

config EFI_RUNTIME_SET_VARIABLE
   depends on EFI_RUNTIME_GET_VARIABLE
   select FAT_WRITE

...

I proposed similar idea before, but it was not accepted.
It is time to do that.

Thanks,
-Takahiro Akashi