[MTD] Fix CFI build error when no map width or interleave supported

When building NOR flash support, you have compile-time options for the
bus width and the number of individual chips which are interleaved
together onto that bus. The code to deal with arbitrary geometry is a
bit convoluted, and people want to just configure it for the specific
hardware they have, to avoid the runtime overhead.

Selecting _none_ of the available options doesn't make any sense. You
should have at least one. This makes it build though, since people
persist in trying.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/mtd/cfi.h b/include/linux/mtd/cfi.h
index 123948b14547..e17c5343cf51 100644
--- a/include/linux/mtd/cfi.h
+++ b/include/linux/mtd/cfi.h
@@ -57,6 +57,15 @@
 #define cfi_interleave_is_8(cfi) (0)
 #endif
 
+#ifndef cfi_interleave
+#warning No CONFIG_MTD_CFI_Ix selected. No NOR chip support can work.
+static inline int cfi_interleave(void *cfi)
+{
+        BUG();
+        return 0;
+}
+#endif
+
 static inline int cfi_interleave_supported(int i)
 {
         switch (i) {