From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from tim.rpsys.net ([194.106.48.114]) by bombadil.infradead.org with esmtps (Exim 4.68 #1 (Red Hat Linux)) id 1JJpAu-00072b-Oc for linux-mtd@lists.infradead.org; Tue, 29 Jan 2008 12:02:49 +0000 Subject: [RFC PATCH 1/3]] Add mtd panic_write function pointer From: Richard Purdie To: David Woodhouse , linux-mtd Content-Type: text/plain Date: Tue, 29 Jan 2008 11:59:24 +0000 Message-Id: <1201607964.5017.48.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MTDs are well suited for logging critical data and the mtdoops driver allows kernel panics/oops to be written to flash in a blackbox flight recorder fashion allowing better debugging and analysis of crashes. Any kernel oops in user context can be easily handled since the kernel continues as normal and any queued mtd writes are scheduled. Any kernel oops in interrupt context results in a panic and the delayed writes will not be scheduled however. The existing mtd->write function cannot be called in interrupt context so these messages can never be written to flash. This patch adds a panic_write function pointer that drivers can optionally implement which can be called in interrupt context. It is only intended to be called when its known the kernel is about to panic and we need to write to succeed. Since the kernel is not going to be running for much longer, this function can break locks and delay to ensure the write succeeds (but not sleep). Signed-off-by: Richard Purdie --- drivers/mtd/mtdpart.c | 17 +++++++++++++++++ include/linux/mtd/mtd.h | 2 ++ 2 files changed, 19 insertions(+) Index: kernel-hacking/drivers/mtd/mtdpart.c =================================================================== --- kernel-hacking.orig/drivers/mtd/mtdpart.c 2007-08-11 10:23:37.000000000 +0100 +++ kernel-hacking/drivers/mtd/mtdpart.c 2008-01-29 10:50:51.000000000 +0000 @@ -151,6 +151,20 @@ static int part_write (struct mtd_info * len, retlen, buf); } +static int part_panic_write (struct mtd_info *mtd, loff_t to, size_t len, + size_t *retlen, const u_char *buf) +{ + struct mtd_part *part = PART(mtd); + if (!(mtd->flags & MTD_WRITEABLE)) + return -EROFS; + if (to >= mtd->size) + len = 0; + else if (to + len > mtd->size) + len = mtd->size - to; + return part->master->panic_write (part->master, to + part->offset, + len, retlen, buf); +} + static int part_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_oob_ops *ops) { @@ -352,6 +366,9 @@ int add_mtd_partitions(struct mtd_info * slave->mtd.read = part_read; slave->mtd.write = part_write; + if (master->panic_write) + slave->mtd.panic_write = part_panic_write; + if(master->point && master->unpoint){ slave->mtd.point = part_point; slave->mtd.unpoint = part_unpoint; Index: kernel-hacking/include/linux/mtd/mtd.h =================================================================== --- kernel-hacking.orig/include/linux/mtd/mtd.h 2007-10-15 13:25:38.000000000 +0100 +++ kernel-hacking/include/linux/mtd/mtd.h 2008-01-29 10:50:51.000000000 +0000 @@ -152,6 +152,8 @@ struct mtd_info { int (*read) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf); int (*write) (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf); + int (*panic_write) (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf); + int (*read_oob) (struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops); int (*write_oob) (struct mtd_info *mtd, loff_t to,