[PATCH 2/5] mtd: nand: Propagate mtd_device_unregister() return value in tear down

[Richard Weinberger <richard@nod.at>]

Provide a __nand_release() function for drivers which can deal
with a failing nand release operation.
Most drivers should be safe since they rely on module refcounting.
To catch outliers implement a nand_release() with a WARN_ON().

Signed-off-by: Richard Weinberger <richard@nod.at>
---
 drivers/mtd/nand/nand_base.c | 15 ++++++++++-----
 include/linux/mtd/nand.h     | 12 +++++++++++-
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 0b0dc29..5b9b65b 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -4601,19 +4601,22 @@ int nand_scan(struct mtd_info *mtd, int maxchips)
 EXPORT_SYMBOL(nand_scan);
 
 /**
- * nand_release - [NAND Interface] Free resources held by the NAND device
+ * __nand_release - [NAND Interface] Free resources held by the NAND device
  * @mtd: MTD device structure
  */
-void nand_release(struct mtd_info *mtd)
+int __nand_release(struct mtd_info *mtd)
 {
+	int ret;
 	struct nand_chip *chip = mtd_to_nand(mtd);
 
+	ret = mtd_device_unregister(mtd);
+	if (ret)
+		return ret;
+
 	if (chip->ecc.mode == NAND_ECC_SOFT &&
 	    chip->ecc.algo == NAND_ECC_BCH)
 		nand_bch_free((struct nand_bch_control *)chip->ecc.priv);
 
-	mtd_device_unregister(mtd);
-
 	/* Free bad block table memory */
 	kfree(chip->bbt);
 	if (!(chip->options & NAND_OWN_BUFFERS))
@@ -4623,8 +4626,10 @@ void nand_release(struct mtd_info *mtd)
 	if (chip->badblock_pattern && chip->badblock_pattern->options
 			& NAND_BBT_DYNAMICSTRUCT)
 		kfree(chip->badblock_pattern);
+
+	return 0;
 }
-EXPORT_SYMBOL_GPL(nand_release);
+EXPORT_SYMBOL_GPL(__nand_release);
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index fbe8e16..b3554ec 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -39,7 +39,7 @@ extern int nand_scan_ident(struct mtd_info *mtd, int max_chips,
 extern int nand_scan_tail(struct mtd_info *mtd);
 
 /* Free resources held by the NAND device */
-extern void nand_release(struct mtd_info *mtd);
+extern int __nand_release(struct mtd_info *mtd);
 
 /* Internal helper for board drivers which need to override command function */
 extern void nand_wait_ready(struct mtd_info *mtd);
@@ -1022,6 +1022,16 @@ static inline int jedec_feature(struct nand_chip *chip)
 		: 0;
 }
 
+static inline void nand_release(struct mtd_info *mtd)
+{
+	/*
+	 * If you face this warning your driver is doing something bad.
+	 * Don't issue nand_release() when your MTD is in use.
+	 * Use __nand_release() and handle the error correctly.
+	 */
+	WARN_ON(__nand_release(mtd) != 0);
+}
+
 /*
  * struct nand_sdr_timings - SDR NAND chip timings
  *
-- 
2.7.3