linux-kernel - [PATCH 1/2] mtd: nand: BUG_ON in case of no select_chip and cmd

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Date:	Tue, 19 Jul 2016 08:41:43 -0700
From:	Andrey Smirnov <andrew.smirnov@...il.com>
To:	linux-mtd@...ts.infradead.org
Cc:	Andrey Smirnov <andrew.smirnov@...il.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Richard Weinberger <richard@....at>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] mtd: nand: BUG_ON in case of no select_chip and cmd_ctrl

If no user specified chip->select_chip() function is provided, code in
nand_base.c will automatically set this hook to nand_select_chip(),
which in turn depends on chip->cmd_ctrl() hook being valid. Not
providing both of those functions in NAND controller driver (for example
by mistake) will result in a bit cryptic segfault. Replace it with
explicit BUG_ON statement so it would be obvious what went wrong.

Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
---
 drivers/mtd/nand/nand_base.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index ce7b2ca..57043a6 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -3128,8 +3128,10 @@ static void nand_set_defaults(struct nand_chip *chip, int busw)
 	if (chip->waitfunc == NULL)
 		chip->waitfunc = nand_wait;
 
-	if (!chip->select_chip)
+	if (!chip->select_chip) {
+		BUG_ON(!chip->cmd_ctrl);
 		chip->select_chip = nand_select_chip;
+	}
 
 	/* set for ONFI nand */
 	if (!chip->onfi_set_features)
-- 
2.5.5