Decompiled 2 functions, unable to decompile 1.

sub_81C795C could not be decompiled due to register naming issues.
However, its structure was correctly matched, so I have left the C
code and a comment explaining the issue.

asm/pokenav.s

@@ -5,115 +5,6 @@
 
 	.text
 
-	thumb_func_start atk47_cmd47
-atk47_cmd47: @ 81C78D4
-	push {lr}
-	cmp r0, 0x1
-	beq _081C78EA
-	cmp r0, 0x1
-	bgt _081C78E4
-	cmp r0, 0
-	beq _081C78EA
-	b _081C7914
-_081C78E4:
-	cmp r0, 0x2
-	beq _081C78EE
-	b _081C7914
-_081C78EA:
-	movs r0, 0
-	b _081C7916
-_081C78EE:
-	movs r1, 0xC0
-	lsls r1, 1
-	movs r0, 0
-	movs r2, 0x1
-	bl ChangeBgY
-	ldr r1, =0x00001fff
-	cmp r0, r1
-	bhi _081C7908
-	movs r0, 0x2
-	b _081C7916
-	.pool
-_081C7908:
-	movs r1, 0x80
-	lsls r1, 6
-	movs r0, 0
-	movs r2, 0
-	bl ChangeBgY
-_081C7914:
-	movs r0, 0x4
-_081C7916:
-	pop {r1}
-	bx r1
-	thumb_func_end atk47_cmd47
-
-	thumb_func_start sub_81C791C
-sub_81C791C: @ 81C791C
-	push {lr}
-	movs r1, 0xC0
-	lsls r1, 1
-	movs r0, 0
-	movs r2, 0x2
-	bl ChangeBgY
-	cmp r0, 0
-	ble _081C7932
-	movs r0, 0x2
-	b _081C793E
-_081C7932:
-	movs r0, 0
-	movs r1, 0
-	movs r2, 0
-	bl ChangeBgY
-	movs r0, 0x4
-_081C793E:
-	pop {r1}
-	bx r1
-	thumb_func_end sub_81C791C
-
-	thumb_func_start sub_81C7944
-sub_81C7944: @ 81C7944
-	push {lr}
-	lsls r1, 1
-	ldr r3, =gPlttBufferUnfaded
-	adds r1, r3
-	lsls r2, 10
-	lsrs r2, 11
-	bl CpuSet
-	pop {r0}
-	bx r0
-	.pool
-	thumb_func_end sub_81C7944
-
-	thumb_func_start sub_81C795C
-sub_81C795C: @ 81C795C
-	push {r4,lr}
-	adds r4, r0, 0
-	b _081C7974
-_081C7962:
-	lsls r0, r1, 4
-	movs r2, 0x80
-	lsls r2, 1
-	adds r1, r0, r2
-	ldr r0, [r4]
-	movs r2, 0x20
-	bl sub_81C7944
-	adds r4, 0x8
-_081C7974:
-	ldr r0, [r4]
-	cmp r0, 0
-	beq _081C7988
-	ldrh r0, [r4, 0x4]
-	bl AllocSpritePalette
-	lsls r0, 24
-	lsrs r1, r0, 24
-	cmp r1, 0xFF
-	bne _081C7962
-_081C7988:
-	pop {r4}
-	pop {r0}
-	bx r0
-	thumb_func_end sub_81C795C
-
 	thumb_func_start sub_81C7990
 sub_81C7990: @ 81C7990
 	push {lr}
@@ -4401,7 +4292,7 @@ _081C9A5C:
 	ldr r0, =gPokenavMessageBox_Pal
 	movs r1, 0x10
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	movs r0, 0x1
 	movs r1, 0
 	movs r2, 0
@@ -4454,7 +4345,7 @@ _081C9AFA:
 	ldr r0, =gUnknown_0861FD4C
 	movs r1, 0x20
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	b _081C9AD6
 	.pool
 _081C9B30:
@@ -4481,7 +4372,7 @@ _081C9B3E:
 	ldr r0, =gUnknown_0861FC78
 	movs r1, 0x30
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	bl sub_81C9894
 	cmp r0, 0x3
 	beq _081C9B76
@@ -6152,7 +6043,7 @@ sub_81CA850: @ 81CA850
 	ldr r0, =gUnknown_0861FC78 + 0xE
 	movs r1, 0x31
 	movs r2, 0x4
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	pop {r0}
 	bx r0
 	.pool
@@ -7636,7 +7527,7 @@ _081CB368:
 	ldr r0, =gUnknown_08622510
 	movs r1, 0x20
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	movs r0, 0x2
 	b _081CB418
 	.pool
@@ -7669,7 +7560,7 @@ _081CB3E0:
 	ldr r0, =gUnknown_086226E0
 	movs r1, 0x10
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	movs r0, 0x1
 _081CB418:
 	bl CopyBgTilemapBufferToVram
@@ -7693,11 +7584,11 @@ _081CB424:
 	ldr r0, =gUnknown_08622700
 	movs r1, 0x30
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	ldr r0, =gUnknown_08622720
 	movs r1, 0x50
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	movs r0, 0
 	b _081CB506
 	.pool
@@ -10555,11 +10446,11 @@ sub_81CCA1C: @ 81CCA1C
 	ldr r0, =gUnknown_08622868
 	movs r1, 0x10
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	ldr r0, =gHoennMapZoomIcons_Pal
 	movs r1, 0x30
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	bl sub_8124658
 	lsls r0, 24
 	cmp r0, 0
@@ -13180,11 +13071,11 @@ _081CDFF2:
 	ldr r0, =gPokenavCondition_Pal
 	movs r1, 0x10
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	ldr r0, =gUnknown_08623208
 	movs r1, 0xF0
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	ldr r0, =0x00001814
 	adds r1, r5, r0
 	ldr r0, =0x0000ffb0
@@ -13211,7 +13102,7 @@ _081CE03C:
 	ldr r0, =gUnknown_086231E8
 	movs r1, 0x30
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	movs r0, 0x2
 	bl sub_81D21DC
 	b _081CDFB0
@@ -15659,7 +15550,7 @@ _081CF454:
 	ldr r0, =gUnknown_086233C4
 	movs r1, 0x10
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	movs r0, 0x1
 	bl CopyBgTilemapBufferToVram
 _081CF498:
@@ -15683,7 +15574,7 @@ _081CF4C0:
 	ldr r0, =gUnknown_08623570
 	movs r1, 0x20
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	bl sub_81CF88C
 	b _081CF498
 	.pool
@@ -17043,7 +16934,7 @@ _081CFEF4:
 	ldr r0, =gUnknown_086235E4
 	movs r1, 0x10
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	movs r0, 0x1
 	bl CopyBgTilemapBufferToVram
 _081CFF32:
@@ -17077,7 +16968,7 @@ _081CFF76:
 	ldr r0, =gUnknown_08623790
 	movs r1, 0x20
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	bl sub_81D0304
 	b _081CFF32
 	.pool
@@ -18580,7 +18471,7 @@ _081D0AB8:
 	ldr r0, =gUnknown_08DDE010
 	movs r1, 0x10
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	b _081D0BBA
 	.pool
 _081D0B04:
@@ -18618,11 +18509,11 @@ _081D0B12:
 	ldr r0, =gUnknown_08623FF8
 	movs r1, 0x20
 	movs r2, 0xA0
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	ldr r0, =gUnknown_08624098
 	movs r1, 0xA0
 	movs r2, 0x20
-	bl sub_81C7944
+	bl CopyPaletteIntoBufferUnfaded
 	movs r0, 0x1
 	b _081D0BBC
 	.pool

src/pokenav_main.c

@@ -13,9 +13,15 @@
 #include "bg.h"
 #include "menu.h"
 #include "graphics.h"
+#include "gba/macro.h"
 
 #define UNKNOWN_OFFSET 100000
 
+struct PaletteDescriptor {
+	void *palette;
+	u16 tag;
+};
+
 struct UnknownStruct_0203CF40 {
 	u32 (*field0)(void);
 	u32 field4;
@@ -49,14 +55,12 @@ extern void sub_81CAADC(void);
 extern void sub_81C99D4(void);
 extern void sub_81C7C94(void);
 extern void sub_8199D98(void);
-extern void sub_81C7944(void* palette, u32 a1, u32 a2);
 extern void sub_81C7B74(void);
 extern void sub_81C7C28(void);
 extern void sub_81C7D28(void);
-extern u32 atk47_cmd47(s32 a0);
-extern u32 sub_81C791C(s32 a0);
 
 
+u32 sub_81C791C(s32 a0);
 bool32 sub_81C756C(u32 a0);
 bool32 sub_81C76C4(void);
 u32 AnyMonHasRibbon(void);
@@ -65,7 +69,9 @@ u32 sub_81C75D4(void);
 u32 sub_81C76FC(void);
 u32 sub_81C786C(void);
 u32 sub_81C7764(s32 a0);
+u32 atk47_cmd47(s32 a0);
 bool32 sub_81C7738(void);
+void CopyPaletteIntoBufferUnfaded(void *palette, u32 a1, u32 a2);
 void sub_81C7834(u32 (*a0)(void), u32(*a1)(void));
 void sub_81C7360(struct UnknownStruct_0203CF40 *a0);
 void sub_81C7650(u32 index);
@@ -493,7 +499,7 @@ u32 sub_81C7764(s32 a0) {
 		decompress_and_copy_tile_data_to_vram(0, &gPokenavHeader_Gfx, 0, 0, 0);
 		SetBgTilemapBuffer(0, &v1->data[11]);
 		CopyToBgTilemapBuffer(0, &gPokenavHeader_Tilemap, 0, 0);
-		sub_81C7944(&gPokenavHeader_Pal, 0, 0x20);
+		CopyPaletteIntoBufferUnfaded(&gPokenavHeader_Pal, 0, 0x20);
 		CopyBgTilemapBufferToVram(0);
 		return 0;
 	case 2:
@@ -566,4 +572,89 @@ bool32 sub_81C78C0(void) {
 
 	v1 = sub_81C763C(0);
 	return sub_81C70D8(v1->fieldC);
+}
+
+u32 atk47_cmd47(s32 a0) {
+	switch (a0) {
+	default:
+		return 4;
+	case 1:
+		return 0;
+	case 0:
+		return 0;
+	case 2:
+		if ((u32)ChangeBgY(0, 384, 1) >= 0x2000) {
+			ChangeBgY(0, 0x2000, 0);
+			return 4;
+		} else {
+			return 2;
+		}
+	}
+}
+
+u32 sub_81C791C(s32 a0) {
+	if (ChangeBgY(0, 384, 2) <= 0) {
+		ChangeBgY(0, 0, 0);
+		return 4;
+	} else {
+		return 2;
+	}
+}
+
+void CopyPaletteIntoBufferUnfaded(void *palette, u32 bufferOffset, u32 size) {
+	CpuCopy16(palette, gPlttBufferUnfaded + bufferOffset, size);
+}
+
+__attribute__((naked))
+void sub_81C795C(struct PaletteDescriptor *palettes) {
+	// This code matches the assembly almost exactly; however, gcc chooses
+	// to store `index` in r0 instead of r1.
+#ifdef NONMATCHING
+	struct PaletteDescriptor *current;
+	u32 offset;
+	u32 index;
+	
+	current = palettes;
+	for (;;) {
+		if (current->palette == NULL) {
+			break;
+		}
+		index = AllocSpritePalette(current->tag);
+		if (index == 0xFF) {
+			break;
+		}
+		offset = (index * 16) + 0x100;
+		CopyPaletteIntoBufferUnfaded(current->palette, offset, 0x20);
+		current++;
+	}
+#else // NONMATCHING
+	asm(".syntax unified\n\
+		push {r4,lr}\n\
+		adds r4, r0, 0\n\
+		b _081C7974\n\
+	_081C7962:\n\
+		lsls r0, r1, 4\n\
+		movs r2, 0x80\n\
+		lsls r2, 1\n\
+		adds r1, r0, r2\n\
+		ldr r0, [r4]\n\
+		movs r2, 0x20\n\
+		bl CopyPaletteIntoBufferUnfaded\n\
+		adds r4, 0x8\n\
+	_081C7974:\n\
+		ldr r0, [r4]\n\
+		cmp r0, 0\n\
+		beq _081C7988\n\
+		ldrh r0, [r4, 0x4]\n\
+		bl AllocSpritePalette\n\
+		lsls r0, 24\n\
+		lsrs r1, r0, 24\n\
+		cmp r1, 0xFF\n\
+		bne _081C7962\n\
+	_081C7988:\n\
+		pop {r4}\n\
+		pop {r0}\n\
+		bx r0\n\
+		.syntax divided");
+#endif // NONMATCHING
 }