linux-kernel - [PATCH for-4.4] mtd: nand: assign reasonable default name for NAND drivers

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Message-Id: <1451934663-68925-1-git-send-email-computersforpeace@gmail.com>
Date:	Mon,  4 Jan 2016 11:11:03 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	<linux-mtd@...ts.infradead.org>
Cc:	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Brian Norris <computersforpeace@...il.com>,
	<linux-kernel@...r.kernel.org>, Heiko Schocher <hs@...x.de>,
	Frans Klaver <fransklaver@...il.com>
Subject: [PATCH for-4.4] mtd: nand: assign reasonable default name for NAND drivers

Commits such as commit 853f1c58c4b2 ("mtd: nand: omap2: show parent
device structure in sysfs") attempt to rely on the core MTD code to set
the MTD name based on the parent device. However, nand_base tries to set
a different default name according to the flash name (e.g., extracted
from the ONFI parameter page), which means NAND drivers will never make
use of the MTD defaults. This is not the intention of commit
853f1c58c4b2.

This results in problems when trying to use the cmdline partition
parser, since the MTD name is different than expected. Let's fix this by
providing a default NAND name, where possible.

Note that this is not really a great default name in the long run, since
this means that if there are multiple MTDs attached to the same
controller device, they will have the same name. But that is an existing
issue and requires future work on a better controller vs. flash chip
abstraction to fix properly.

Reported-by: Heiko Schocher <hs@...x.de>
Signed-off-by: Brian Norris <computersforpeace@...il.com>
Cc: Heiko Schocher <hs@...x.de>
Cc: Frans Klaver <fransklaver@...il.com>
---
This patch is needed in additon to commit 472b444eef93 ("mtd: fix cmdlinepart
parser, early naming for auto-filled MTD") to fix Heiko's reported problem. At
this point, I'm not sure if this should be targeted toward late 4.4 or for 4.5.
It's a 4.4 regresssion, but a very small one. And I'm not sure if this will
have wide enough impact that it should be given a longer time to be reviewed
and tested. We can always send it to -stable later, if it's really needed.

 drivers/mtd/nand/nand_base.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index ece544efccc3..9f169566fba4 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -3826,6 +3826,9 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd,
 	if (!type)
 		type = nand_flash_ids;

+	if (!mtd->name && mtd->dev.parent)
+		mtd->name = dev_name(mtd->dev.parent);
+
 	for (; type->name != NULL; type++) {
 		if (is_full_id_nand(type)) {
 			if (find_full_id_nand(mtd, chip, type, id_data, &busw))
-- 
2.6.0.rc2.230.g3dd15c0

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