Re: [mtd/sbc_gxx] kernel BUG at include/linux/mtd/map.h:148!

[Michal Marek <mmarek@suse.cz>]

On Mon, Mar 31, 2014 at 07:34:12PM +0800, Fengguang Wu wrote:
> CC Michal and kbuild list.
> 
> On Thu, Mar 27, 2014 at 04:51:53PM -0600, Bjorn Helgaas wrote:
> > [+cc David, Brian]
> > 
> > On Thu, Mar 27, 2014 at 8:01 AM, Fengguang Wu <fengguang.wu@intel.com> wrote:
> > > FYI, here is a very old warning, too old to be bisected.
> > >
> > > [    5.282127] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
> > > [    5.286079] SBC-GXx flash: IO:0x258-0x259 MEM:0xdc000-0xdffff
> > > [    5.288723] ------------[ cut here ]------------
> > > [    5.289649] kernel BUG at include/linux/mtd/map.h:148!
> > 
> > I think the problem is that your randconfig happens to have none of
> > CONFIG_MTD_MAP_BANK_WIDTH_* set (you should have played the lottery
> > today!), and the default implementation of map_bankwidth() in that
> > case is just "BUG()":
> > 
> >   $ grep MTD_MAP config-3.14.0-rc8-wl-03045-gdf16ea4
> >   # CONFIG_MTD_MAP_BANK_WIDTH_1 is not set
> >   # CONFIG_MTD_MAP_BANK_WIDTH_2 is not set
> >   # CONFIG_MTD_MAP_BANK_WIDTH_4 is not set
> >   # CONFIG_MTD_MAP_BANK_WIDTH_8 is not set
> >   # CONFIG_MTD_MAP_BANK_WIDTH_16 is not set
> >   # CONFIG_MTD_MAP_BANK_WIDTH_32 is not set
> > 
> > I don't know enough Kconfig or MTD to fix this.
> 
> Michal, the problem we run into is, how to select one of the above
> CONFIG_MTD_MAP_BANK_WIDTH_xx in "make randconfig".

You can't enforce this in Kconfig. What you can do is to make the logic
more fool-proof and fall back to some sensible default if none of the
CONFIG_MTD_MAP_BANK_WIDTH_* options is enabled. Like this


From 76e66ceea7e2ffbb1d39c01af2eaf6f2b66c2be3 Mon Sep 17 00:00:00 2001
From: Michal Marek <mmarek@suse.cz>
Date: Mon, 31 Mar 2014 16:25:32 +0200
Subject: [PATCH] mtd: Fall back to MTD_MAP_BANK_WIDTH_1 if none is specified

This is mainly to fix make randconfig errors.

Signed-off-by: Michal Marek <mmarek@suse.cz>
---
 drivers/mtd/chips/Kconfig | 8 ++++++++
 include/linux/mtd/map.h   | 4 ++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/chips/Kconfig b/drivers/mtd/chips/Kconfig
index e4696b3..219de49 100644
--- a/drivers/mtd/chips/Kconfig
+++ b/drivers/mtd/chips/Kconfig
@@ -115,6 +115,14 @@ config MTD_MAP_BANK_WIDTH_32
 	  If you wish to support CFI devices on a physical bus which is
 	  256 bits wide, say 'Y'.
 
+config HAVE_MTD_MAP_BANK_WIDTH_1
+	bool
+	default MTD_MAP_BANK_WIDTH_1 || (!MTD_MAP_BANK_WIDTH_2 && !MTD_MAP_BANK_WIDTH_4 && !MTD_MAP_BANK_WIDTH_8 && !MTD_MAP_BANK_WIDTH_16 && !MTD_MAP_BANK_WIDTH_32)
+
+if HAVE_MTD_MAP_BANK_WIDTH_1 && !MTD_MAP_BANK_WIDTH_1
+comment "no buswidth selected, using 8-bit as a fallback "
+endif
+
 config MTD_CFI_I1
 	bool "Support 1-chip flash interleave" if MTD_CFI_GEOMETRY
 	default y
diff --git a/include/linux/mtd/map.h b/include/linux/mtd/map.h
index 5f487d7..d4f4f49 100644
--- a/include/linux/mtd/map.h
+++ b/include/linux/mtd/map.h
@@ -32,7 +32,7 @@
 #include <asm/io.h>
 #include <asm/barrier.h>
 
-#ifdef CONFIG_MTD_MAP_BANK_WIDTH_1
+#ifdef CONFIG_HAVE_MTD_MAP_BANK_WIDTH_1
 #define map_bankwidth(map) 1
 #define map_bankwidth_is_1(map) (map_bankwidth(map) == 1)
 #define map_bankwidth_is_large(map) (0)
@@ -156,7 +156,7 @@ static inline int map_bankwidth(void *map)
 static inline int map_bankwidth_supported(int w)
 {
 	switch (w) {
-#ifdef CONFIG_MTD_MAP_BANK_WIDTH_1
+#ifdef CONFIG_HAVE_MTD_MAP_BANK_WIDTH_1
 	case 1:
 #endif
 #ifdef CONFIG_MTD_MAP_BANK_WIDTH_2
-- 
1.8.4.5