[PATCH] ARM: mach-rpc: fix zImage build after recent font-related changes

[Ethan Nelson-Moore <enelsonmoore@gmail.com>]

The text display code used in the Risc PC kernel image decompression
code uses arch/arm/boot/compressed/font.c, which includes
lib/fonts/font_acorn_8x8.c, which further includes <linux/font.h>.

Since commit 97df8960240a ("lib/fonts: Provide helpers for calculating
glyph pitch and size") <linux/font.h> contains inline functions that
require __do_div64, which is not linked into the ARM kernel
decompressor. This makes Risc PC zImages fail to build.

Resolve this issue in the least intrusive way possible by preventing
the inclusion of <linux/font.h> (and the definition of a struct that
relies on it) when the decompressor is being built.

Fixes: 97df8960240a ("lib/fonts: Provide helpers for calculating glyph pitch and size")
Signed-off-by: Ethan Nelson-Moore <enelsonmoore@gmail.com>
---
 arch/arm/boot/compressed/Makefile | 6 +++++-
 lib/fonts/font_acorn_8x8.c        | 2 ++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index a159120d1e42..0e198a6ce447 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -157,4 +157,8 @@ $(obj)/piggy_data: $(obj)/../Image FORCE
 
 $(obj)/piggy.o: $(obj)/piggy_data
 
-CFLAGS_font.o := -Dstatic=
+# Defining _VIDEO_FONT_H prevents including <linux/font.h>, which contains
+# inline functions that require __do_div64, which is not linked into the
+# decompressor. OMIT_FONT_DESC is used in lib/fonts/font_acorn_8x8.c to omit the
+# definition of the font's font_desc structure, which requires <linux/font.h>.
+CFLAGS_font.o := -Dstatic= -D_VIDEO_FONT_H -DOMIT_FONT_DESC
diff --git a/lib/fonts/font_acorn_8x8.c b/lib/fonts/font_acorn_8x8.c
index 36c51016769d..6b5291c23fc8 100644
--- a/lib/fonts/font_acorn_8x8.c
+++ b/lib/fonts/font_acorn_8x8.c
@@ -265,6 +265,7 @@ static const struct font_data acorndata_8x8 = {
 /* FF */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 } };
 
+#ifndef OMIT_FONT_DESC /* Used by arch/arm/boot/compressed/Makefile */
 const struct font_desc font_acorn_8x8 = {
 	.idx	= ACORN8x8_IDX,
 	.name	= "Acorn8x8",
@@ -278,3 +279,4 @@ const struct font_desc font_acorn_8x8 = {
 	.pref	= 0,
 #endif
 };
+#endif /* OMIT_FONT_DESC */
-- 
2.43.0