linux-kernel - Re: [patch] MTD: fix cfi

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Message-Id: <1191223312.9188.3.camel@pmac.infradead.org>
Date:	Mon, 01 Oct 2007 08:21:52 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch] MTD: fix cfi_interleave() build errors

On Mon, 2007-10-01 at 09:14 +0200, Ingo Molnar wrote:
> MTD is the only code in the tree at the moment that breaks "make 
> randconfig" tests (after ~2000 random rebuilds) - and those tests _are_ 
> immensely useful, they catch a lot of build breakage in the scheduler 
> git tree for example, before i push it out. So if possible it would be 
> nice to have this in .23.

I did send it, a number of weeks ago. Linus didn't take it, so I just
put it in the git tree for 2.6.24. Now I think it's too late, but here
it is again in case Linus has changed his mind...

commit 241651d04d672fb685b2874707016cbbf95931e5
Author: David Woodhouse <dwmw2@...radead.org>
Date:   Thu Sep 6 09:40:21 2007 +0100

[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@...radead.org>

diff --git a/include/linux/mtd/cfi.h b/include/linux/mtd/cfi.h
index 123948b..e17c534 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) {
diff --git a/include/linux/mtd/map.h b/include/linux/mtd/map.h
index 81f3a31..a9fae03 100644
--- a/include/linux/mtd/map.h
+++ b/include/linux/mtd/map.h
@@ -125,7 +125,15 @@
 #endif
 
 #ifndef map_bankwidth
-#error "No bus width supported. What's the point?"
+#warning "No CONFIG_MTD_MAP_BANK_WIDTH_xx selected. No NOR chip support can work"
+static inline int map_bankwidth(void *map)
+{
+	BUG();
+	return 0;
+}
+#define map_bankwidth_is_large(map) (0)
+#define map_words(map) (0)
+#define MAX_MAP_BANKWIDTH 1
 #endif
 
 static inline int map_bankwidth_supported(int w)

-- 
dwmw2

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