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Added scramble flags to RGBLINK. (#921)

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* Add scramble flags to RGBLINK

-S and -W will scramble ROMX and WRAMX respectively.

* Modify scramble CLI

CLI now takes a list of comma-separated values.
Added arg_error to clean up messages.

Co-authored-by: Eldred Habert <eldredhabert0@gmail.com>

* Document scrambling functionality

Co-authored-by: Eldred Habert <eldredhabert0@gmail.com>
This commit is contained in:
Eievui
2021-10-31 17:58:26 -04:00
committed by GitHub
parent 11a6a81169
commit 8b1cc72f09
5 changed files with 254 additions and 22 deletions
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59
src/link/rgblink.1
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@@ -20,6 +20,7 @@
.Op Fl O Ar overlay_file
.Op Fl o Ar out_file
.Op Fl p Ar pad_value
.Op Fl S Ar spec
.Op Fl s Ar symbol
.Ar
.Sh DESCRIPTION
@@ -89,6 +90,14 @@ Has no effect if
.Fl O
is specified.
The default is 0.
.It Fl S Ar spec , Fl Fl scramble Ar spec
Enables a different
.Dq scrambling
algorithm for placing sections.
See
.Sx Scrambling algorithm
below for an explanation and a description of
.Ar spec .
.It Fl s Ar symbol , Fl Fl smart Ar symbol
This option is ignored.
It was supposed to perform smart linking but fell into disrepair, and so has been removed.
@@ -113,6 +122,56 @@ When making a ROM, be careful that not using this is not a replacement for
.Xr rgbfix 1 Ap s Fl p
option!
.El
.Ss Scrambling algorithm
The default section placement algorithm tries to minimize the number of banks used;
.Dq scrambling
instead places sections into a given pool of banks, trying to minimize the number of sections sharing a given bank.
This is useful to catch broken bank assumptions, such as expecting two different sections to land in the same bank (that is not guaranteed unless both are manually assigned the same bank number).
.Pp
A scrambling spec is a comma-separated list of region specs.
A trailing comma is allowed, as well as whitespace between all specs and their components.
Each region spec has the following form:
.D1 Ar region Ns Op = Ns Ar size
.Ar region
must be one of the following (case-insensitive), while
.Ar size
must be a positive decimal integer between 1 and the corresponding maximum.
Certain regions allow omitting the size, in which case it defaults to its max value.
.Bl -column "Region name" "Max value" "Size optional"
Region name Ta Max size Ta Size optional
.Cm romx Ta 65535 Ta \&No
.Cm sram Ta 255 Ta \&No
.Cm wramx Ta 7 Ta Yes
.El
.Pp
A
.Ar size
of 0 disables scrambling for that region.
.Pp
For example,
.Ql romx=64,wramx=4
will scramble
.Ic ROMX
sections among ROM banks 1 to 64,
.Ic WRAMX
sections among RAM banks 1 to 4, and will not scramble
.Ic SRAM
sections.
.Pp
Later region specs override earlier ones; for example,
.Ql romx=42, Romx=0
disables scrambling for
.Cm romx .
.Pp
.Cm wramx
scrambling is silently ignored if
.Fl w
is passed (including if implied by
.Fl d ) ,
as
.Ic WRAMX
sections will be treated as
.Ic WRAM0 .
.Sh EXAMPLES
All you need for a basic ROM is an object file, which can be made into a ROM image like so:
.Pp