[SeaBIOS] Re: [PATCH v2] make BUILD_MIN_BIOSTABLE configurable

[Kevin O'Connor]

On Thu, May 27, 2021 at 10:52:27AM +0200, Gerd Hoffmann wrote:
> BUILD_MIN_BIOSTABLE reserves space in the f-segment.  Some data
> structures -- for example disk drives known to seabios -- must be
> stored there, so the space available here limits the number of
> devices seabios is able to manage.
>
> This patch adds an config option for BUILD_MIN_BIOSTABLE so the size of
> the reservation can be configured at build time.  Default is 8k for bios
> images being 256k or larger in size (32bit code is moved off then so we
> have more room in the f-segment), 2k (current value) otherwise.

I'm not sure it is a good idea to make this a user configurable value.
I'm concerned that it's too easy to set it to a value that breaks
things.  Is there any harm in setting it to 8K unconditionally?
> Signed-off-by: Gerd Hoffmann
>
> Makefile             | 2 +-
>  scripts/layoutrom.py | 3 ++-
>  src/Kconfig          | 7 +++++++
>  3 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 3d8943ef5f25..ddcd1dff399d 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -172,7 +172,7 @@ $(OUT)romlayout16.lds: $(OUT)ccode32flat.o $(OUT)code32seg.o $(OUT)ccode16.o $(O
>    $(Q)$(OBJDUMP) -thr $(OUT)code32flat.o > $(OUT)code32flat.o.objdump
>    $(Q)$(OBJDUMP) -thr $(OUT)code32seg.o > $(OUT)code32seg.o.objdump
>    $(Q)$(OBJDUMP) -thr $(OUT)code16.o > $(OUT)code16.o.objdump
> $(Q)$(PYTHON) ./scripts/layoutrom.py $(OUT)code16.o.objdump $(OUT)code32seg.o.objdump $(OUT)code32flat.o.objdump $(OUT)$(KCONFIG_AUTOHEADER) $(OUT)romlayout16.lds $(OUT)romlayout32seg.lds $(OUT)romlayout32flat.lds
> $(Q)$(PYTHON) ./scripts/layoutrom.py $(OUT)code16.o.objdump $(OUT)code32seg.o.objdump $(OUT)code32flat.o.objdump $(OUT)$(KCONFIG_AUTOHEADER) $(OUT)romlayout16.lds $(OUT)romlayout32seg.lds $(OUT)romlayout32flat.lds $(CONFIG_MIN_BIOSTABLE)
>
> # These are actually built by scripts/layoutrom.py above, but by pulling them
>  # into an extra rule we prevent make -j from spawning layoutrom.py 4 times.
> diff --git a/scripts/layoutrom.py b/scripts/layoutrom.py
> index 6616721d1b58..94deca9fcc85 100755
> --- a/scripts/layoutrom.py
> +++ b/scripts/layoutrom.py
> @@ -636,7 +636,8 @@ def scanconfig(file):
>
> def main():
>      # Get output name
> in16, in32seg, in32flat, cfgfile, out16, out32seg, out32flat = sys.argv[1:]
> in16, in32seg, in32flat, cfgfile, out16, out32seg, out32flat, biostable = sys.argv[1:]
> BUILD_MIN_BIOSTABLE = biostable * 1024

FYI, the layoutrom.py script reads in the Kconfig file explicitly a
few lines down.  If we do want to have a setting in Kconfig, I think
it should be taken directly from Kconfig instead of passed from the
command-line.

Cheers,
-Kevin
>  # Read in the objdump information
>  infile16 = open(in16, 'r')
>
> diff --git a/src/Kconfig b/src/Kconfig
> index 3a8ffa15fded..95519fc50fa3 100644
> --- a/src/Kconfig
> +++ b/src/Kconfig
> @@ -140,6 +140,13 @@ endchoice
>              it into 128 KB (which was big enouth for a long time) you'll
>              probably have to disable some featues such as xhci support.
> config MIN_BIOSTABLE
>    int "biostable size (in KB)"
>    default 8 if ROM_SIZE >= 256
>    default 2
>    help
>        Memory space for BIOS tables in f-segment.
>
> endmenu
> menu "Hardware support"
>
> 2.31.1
>
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