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Date: Mon, 31 Mar 2014 19:34:12 +0800
From: Fengguang Wu <fengguang.wu@intel.com>
To: Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [mtd/sbc_gxx] kernel BUG at include/linux/mtd/map.h:148!
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Cc: Michal Marek <mmarek@suse.cz>, linux-kbuild <linux-kbuild@vger.kernel.org>,
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 "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
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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".

Thanks,
Fengguang