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From: "David Byron" <dbyron@hheld.com>
To: <linux-mtd@lists.infradead.org>
Subject: initializing chip->wq in cfi_cmdset_0002.c
Date: Sat, 1 Jul 2006 11:18:02 -0700
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I'm using cfi_cmdset_0002.c to access a flash chip and I ran into an oops
from trying to dereference a null pointer.  I found a fix for it, but I feel
like there must be something I don't understand.  Seems like other folks
would have run into this as well.

The crash comes with the call to wake_up(&chip->wq) on the last line of
put_chip.  I can't see anywhere that this data structure is initialized.  I
looked at some of the other cfi_cmdset* files and decided that

diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c
b/drivers/mtd/chips/cfi_cmdset_0002.c
index 9885726..8a390b3 100644
--- a/drivers/mtd/chips/cfi_cmdset_0002.c
+++ b/drivers/mtd/chips/cfi_cmdset_0002.c
@@ -320,6 +320,7 @@ #endif
 		cfi->chips[i].word_write_time =
1<<cfi->cfiq->WordWriteTimeoutTyp;
 		cfi->chips[i].buffer_write_time =
1<<cfi->cfiq->BufWriteTimeoutTyp;
 		cfi->chips[i].erase_time =
1<<cfi->cfiq->BlockEraseTimeoutTyp;
+		init_waitqueue_head(&cfi->chips[i].wq);
 	}
 
 	map->fldrv = &cfi_amdstd_chipdrv;

was a good place to initialize.  It fixes the oops for me.  Can someone
confirm that this makes sense?

Thanks much.

-DB