build: explicitly set ROM size

Add a config option to specify the rom size wanted.  Default is zero,
which will automatically figure the needed size.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/Makefile b/Makefile
index d763ae3..283938a 100644
--- a/Makefile
+++ b/Makefile
@@ -178,7 +178,8 @@
 	@echo "  Prepping $@"
 	$(Q)$(OBJDUMP) -thr $< > $<.objdump
 	$(Q)$(OBJCOPY) -O binary $< $(OUT)bios.bin.raw
-	$(Q)$(PYTHON) ./scripts/checkrom.py $<.objdump $(OUT)bios.bin.raw $(OUT)bios.bin
+	$(Q)$(PYTHON) ./scripts/checkrom.py $<.objdump $(CONFIG_ROM_SIZE) \
+		$(OUT)bios.bin.raw $(OUT)bios.bin
 	$(Q)$(STRIP) -R .comment $< -o $(OUT)bios.bin.elf
 
 
diff --git a/scripts/checkrom.py b/scripts/checkrom.py
index 6f07ac8..aa3dd0d 100755
--- a/scripts/checkrom.py
+++ b/scripts/checkrom.py
@@ -21,7 +21,7 @@
 
 def main():
     # Get args
-    objinfo, rawfile, outfile = sys.argv[1:]
+    objinfo, finalsize, rawfile, outfile = sys.argv[1:]
 
     # Read in symbols
     objinfofile = open(objinfo, 'rb')
@@ -32,11 +32,20 @@
     rawdata = f.read()
     f.close()
     datasize = len(rawdata)
-    finalsize = 64*1024
-    if datasize > 64*1024:
-        finalsize = 128*1024
-        if datasize > 128*1024:
-            finalsize = 256*1024
+    finalsize = int(finalsize) * 1024
+    if finalsize == 0:
+        finalsize = 64*1024
+        if datasize > 64*1024:
+            finalsize = 128*1024
+            if datasize > 128*1024:
+                finalsize = 256*1024
+    if datasize > finalsize:
+        print "Error!  ROM doesn't fit (%d > %d)" % (datasize, finalsize)
+        print "   You have to either increate the size (CONFIG_ROM_SIZE)"
+        print "   or turn off some features (such as hardware support not"
+        print "   needed) to make it fit.  Trying a more recent gcc version"
+        print "   might work too."
+        sys.exit(1)
 
     # Sanity checks
     start = symbols['code32flat_start'].offset
diff --git a/src/Kconfig b/src/Kconfig
index c40cc61..20d2a3e 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -122,6 +122,17 @@
             selected, the memory is instead allocated from the
             "9-segment" (0x90000-0xa0000).
 
+    config ROM_SIZE
+        int "ROM size (in KB)"
+        default 0
+        help
+            Set the ROM size.  Say '0' here to make seabios figure the
+            needed size automatically.
+
+            Currently SeaBIOS will easily fit into 256 KB. To make it fit
+            it into 128 KB (which was big enouth for a long time) you'll
+            probably have to disable some featues such as xhci support.
+
 endmenu
 
 menu "Hardware support"