Refactor iNES header.

mysterymath · mysterymath · commit 13ff83d9efe2 · 2022-04-13T17:24:55.000-07:00
diff --git a/mos-platform/nes-nrom-128/CMakeLists.txt b/mos-platform/nes-nrom-128/CMakeLists.txt
@@ -1 +1,8 @@
 platform(nes-nrom-128 COMPLETE PARENT nes-nrom)
+
+if(NOT CMAKE_CROSSCOMPILING)
+  return()
+endif()
+
+add_platform_object_file(nes-nrom-128-crt0-o crt0.o ines.s)
+merge_libraries(nes-nrom-128-crt0-o nes-nrom-crt0-o)
diff --git a/mos-platform/nes-nrom-128/ines.s b/mos-platform/nes-nrom-128/ines.s
@@ -0,0 +1,4 @@
+; Settings in the iNES 2.0 header.
+
+.global __prg_rom_size
+__prg_rom_size = 1
diff --git a/mos-platform/nes-nrom-128/link.ld b/mos-platform/nes-nrom-128/link.ld
@@ -9,17 +9,3 @@ MEMORY {
 }
 
 INCLUDE nes-nrom.ld
-
-OUTPUT_FORMAT {
-  INCLUDE ines-header.ld
-
-  /* PRG-ROM size LSB (counting by 16K) */
-  BYTE(1)
-  /* CHR-ROM size LSB (counting by 8K) */
-  BYTE(1)
-
-  INCLUDE ines-flags.ld
-
-  FULL(prg_rom)
-  FULL(chr_rom)
-}
diff --git a/mos-platform/nes-nrom-256/CMakeLists.txt b/mos-platform/nes-nrom-256/CMakeLists.txt
@@ -1 +1,8 @@
 platform(nes-nrom-256 COMPLETE PARENT nes-nrom)
+
+if(NOT CMAKE_CROSSCOMPILING)
+  return()
+endif()
+
+add_platform_object_file(nes-nrom-256-crt0-o crt0.o ines.s)
+merge_libraries(nes-nrom-256-crt0-o nes-nrom-crt0-o)
diff --git a/mos-platform/nes-nrom-256/ines.s b/mos-platform/nes-nrom-256/ines.s
@@ -0,0 +1,4 @@
+; Settings in the iNES 2.0 header.
+
+.global __prg_rom_size
+__prg_rom_size = 2
diff --git a/mos-platform/nes-nrom-256/link.ld b/mos-platform/nes-nrom-256/link.ld
@@ -6,17 +6,3 @@ MEMORY {
 }
 
 INCLUDE nes-nrom.ld
-
-OUTPUT_FORMAT {
-  INCLUDE ines-header.ld
-
-  /* PRG-ROM size LSB (counting by 16K) */
-  BYTE(2)
-  /* CHR-ROM size LSB (counting by 8K) */
-  BYTE(1)
-
-  INCLUDE ines-flags.ld
-
-  FULL(prg_rom)
-  FULL(chr_rom)
-}
diff --git a/mos-platform/nes-nrom/CMakeLists.txt b/mos-platform/nes-nrom/CMakeLists.txt
@@ -4,10 +4,7 @@ if(NOT CMAKE_CROSSCOMPILING)
   return()
 endif()
 
-install(FILES
-  nes-nrom.ld
-  ines-flags.ld
-TYPE LIB)
+install(FILES nes-nrom.ld TYPE LIB)
 
 add_platform_object_file(nes-nrom-crt0-o crt0.o ines.s)
 merge_libraries(nes-nrom-crt0-o nes-crt0-o)
diff --git a/mos-platform/nes-nrom/ines-flags.ld b/mos-platform/nes-nrom/ines-flags.ld
diff --git a/mos-platform/nes-nrom/ines.s b/mos-platform/nes-nrom/ines.s
@@ -1,9 +1,6 @@
-; Defaults for settings in the iNES 2.0 header.
+; Settings in the iNES 2.0 header.
 
-.weak __hard_wired_mirroring
-; Default to horizontal hard-wired mirroring (or N/A)
-__hard_wired_mirroring = 0
-
-.weak __timing
-; Default to RP2C02 ("NTSC NES")
-__timing = 0
+.global __mapper
+__mapper = 0
+.global __chr_rom_size
+__chr_rom_size = 1
diff --git a/mos-platform/nes-nrom/nes-nrom.ld b/mos-platform/nes-nrom/nes-nrom.ld
@@ -1,12 +1,8 @@
 /* NES-NROM iNES file linker script. */
 
-MEMORY {
-  /* CPU address space. */
-  ram (w)      : ORIGIN = 0x0200, LENGTH = 0x0600
-
-  /* CHR-ROM VMA. */
-  ppu_chr_rom : ORIGIN = 0x0000, LENGTH = 0x2000
+INCLUDE nes.ld
 
+MEMORY {
   /**
    * CHR-ROM LMA. Doesn't correspond to anything at runtime; this is beyond
    * 0xffff to make sure that all LMAs are unique.
@@ -23,9 +19,9 @@ SECTIONS {
   INCLUDE bss.ld
   INCLUDE noinit.ld
 
-  .chr_rom : { *(.chr_rom) } >ppu_chr_rom AT>chr_rom
+  .chr_rom : { *(.chr_rom) } >chr_rom
 
   .vector 0xfffa : { SHORT(nmi) SHORT(_start) SHORT(irq) } >prg_rom
 }
 
-INCLUDE nes-imag-regs.ld
+INCLUDE ines.ld
diff --git a/mos-platform/nes-slrom/CMakeLists.txt b/mos-platform/nes-slrom/CMakeLists.txt
@@ -1 +1,8 @@
 platform(nes-slrom COMPLETE PARENT nes-nrom)
+
+if(NOT CMAKE_CROSSCOMPILING)
+  return()
+endif()
+
+add_platform_object_file(nes-slrom-crt0-o crt0.o ines.s)
+merge_libraries(nes-slrom-crt0-o nes-crt0-o)
diff --git a/mos-platform/nes-slrom/ines.s b/mos-platform/nes-slrom/ines.s
@@ -0,0 +1,8 @@
+; Settings in the iNES 2.0 header.
+
+.global __mapper
+__mapper = 1
+.global __prg_rom_size
+__prg_rom_size = 16
+.global __chr_rom_size
+__chr_rom_size = 16
diff --git a/mos-platform/nes-slrom/link.ld b/mos-platform/nes-slrom/link.ld
@@ -1,17 +1,12 @@
 /* NES SLROM iNES file linker script. */
 
-MEMORY {
-  /* CPU address space. */
-  ram (w)      : ORIGIN = 0x0200, LENGTH = 0x0600
+INCLUDE nes.ld
 
+MEMORY {
   /* PRG-ROM VMAs. */
   prg_rom_lo : ORIGIN = 0x8000, LENGTH = 0x4000
   prg_rom_hi : ORIGIN = 0xc000, LENGTH = 0x4000
 
-  /* CHR-ROM VMAs. */
-  chr_rom_lo : ORIGIN = 0x0000, LENGTH = 0x1000
-  chr_rom_hi : ORIGIN = 0x1000, LENGTH = 0x1000
-
   /* PRG-ROM LMA. 256 Kib. */
   prg_rom : ORIGIN = 0x10000, LENGTH = 0x40000
 
@@ -38,66 +33,4 @@ SECTIONS {
   } >prg_rom_15
 }
 
-INCLUDE nes-imag-regs.ld
-
-OUTPUT_FORMAT {
-  INCLUDE ines-header.ld
-
-  /* PRG-ROM size LSB. */
-  BYTE(16)
-
-  /* CHR-ROM size LSB. */
-  BYTE(16)
-
-  /* Flags 6:
-  *   Mapper 0
-  *   No hard-wired four-screen mode.
-  *   No trainer.
-  *   No battery.
-  *   No hard-wired mirroring.
-  */
-  BYTE(0)
-
-  /* Flags 7:
-  *   Mapper 1.
-  *   NES 2.0 identifier.
-  *   NES/Family Computer console type.
-  */
-  BYTE(1 << 4 | 2 << 2 | 0)
-
-  /* Mapper MSB/Submapper:
-  *   Submapper 0.
-  *   Mapper MSB 0.
-  */
-  BYTE(0)
-
-  /* PRG-ROM/CHR-ROM size MSB (counting by 8K) */
-  BYTE(0)
-
-  /* PRG-RAM/EEPROM size
-  *   No PRG-RAM.
-  *   No PRG-EEPROM.
-  */
-  BYTE(0)
-
-  /* CHR-RAM/NVRAM size
-  *   No CHR-RAM.
-  *   No CHR-NVRAM.
-  */
-  BYTE(0)
-
-  /* CPU/PPU Timing */
-  BYTE(__timing)
-
-  /* VS system type/Extended Console Type: N/A */
-  BYTE(0)
-
-  /* Miscellaneous ROMs: 0 */
-  BYTE(0)
-
-  /* Default Expansion Device: N/A */
-  BYTE(0)
-
-  FULL(prg_rom)
-  FULL(chr_rom)
-}
+INCLUDE ines.ld
diff --git a/mos-platform/nes/CMakeLists.txt b/mos-platform/nes/CMakeLists.txt
@@ -7,13 +7,15 @@ endif()
 install(FILES ppu.h TYPE INCLUDE)
 install(FILES
   ppu.h
+  nes.ld
+  ines.ld
   ines-header.ld
+  ines-roms.ld
   nes-imag-regs.ld
+  nes-ram.ld
 TYPE LIB)
 
-add_platform_object_file(nes-crt0-o crt0.o
-  crt0.c
-)
+add_platform_object_file(nes-crt0-o crt0.o crt0.c ines.s)
 merge_libraries(nes-crt0-o common-crt0-o)
 
 add_platform_library(nes-crt0)
diff --git a/mos-platform/nes/ines-header.ld b/mos-platform/nes/ines-header.ld
@@ -1,2 +1,59 @@
-/* Identification string: NES<EOF> */
+/* iNES 2.0 header: https://www.nesdev.org/wiki/NES_2.0 */
+
+/* Note that the "size" fields all have wildly different interpretations; see the
+ * reference above for details. */
+
 BYTE(0x4e) BYTE(0x45) BYTE(0x53) BYTE(0x1a)
+
+BYTE(__prg_rom_size & 0xff)
+
+BYTE(__chr_rom_size & 0xff)
+
+BYTE(
+  (__mirroring   & 1  ) << 0 |
+  (__battery     & 1  ) << 1 |
+  (__trainer     & 1  ) << 2 |
+  (__four_screen & 1  ) << 3 |
+  (__mapper      & 0xf) << 4
+)
+
+BYTE(
+  (__console_type & 3  ) << 0 |
+  2                      << 2 |
+  (__mapper >> 4  & 0xf) << 4
+)
+
+BYTE(
+  (__mapper >> 8 & 0xf) << 0 |
+  (__submapper   & 0xf) << 4
+)
+
+BYTE(
+  (__prg_rom_size >> 8 & 0xf) << 0 |
+  (__chr_rom_size >> 8 & 0xf) << 4
+)
+
+BYTE(
+  (__prg_ram_size   & 0xf) << 0 |
+  (__prg_nvram_size & 0xf) << 4
+)
+
+BYTE(
+  (__chr_ram_size   & 0xf) << 0 |
+  (__chr_nvram_size & 0xf) << 4
+)
+
+BYTE(__timing & 3)
+
+BYTE(
+  (__console_type & 3) == 1 ?
+    (__ppu_type & 0xf) << 0 |
+    (__hw_type  & 0xf) << 4
+  : (__console_type & 3) == 3 ?
+    __extended_console_type & 0xf
+  : 0
+)
+
+BYTE(__misc_roms & 3)
+
+BYTE(__default_expansion_device & 0x3f)
diff --git a/mos-platform/nes/ines-roms.ld b/mos-platform/nes/ines-roms.ld
@@ -0,0 +1,2 @@
+FULL(prg_rom)
+FULL(chr_rom)
diff --git a/mos-platform/nes/ines.ld b/mos-platform/nes/ines.ld
@@ -0,0 +1,4 @@
+OUTPUT_FORMAT {
+  INCLUDE ines-header.ld
+  INCLUDE ines-roms.ld
+}
diff --git a/mos-platform/nes/ines.s b/mos-platform/nes/ines.s
diff --git a/mos-platform/nes/nes-ram.ld b/mos-platform/nes/nes-ram.ld
diff --git a/mos-platform/nes/nes.ld b/mos-platform/nes/nes.ld
