From 388bbb09b991c792310af2f6b49f6c55edb3dff0 Mon Sep 17 00:00:00 2001 From: Richard Purdie Date: Wed, 6 Feb 2008 10:17:15 +0000 Subject: [MTD] Add mtd panic_write function pointer 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 Signed-off-by: David Woodhouse --- drivers/mtd/mtdpart.c | 17 +++++++++++++++++ include/linux/mtd/mtd.h | 9 +++++++++ 2 files changed, 26 insertions(+) diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c index 6174a97d7902..c66902df3171 100644 --- a/drivers/mtd/mtdpart.c +++ b/drivers/mtd/mtdpart.c @@ -151,6 +151,20 @@ static int part_write (struct mtd_info *mtd, loff_t to, size_t len, 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 *master, 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; diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h index 783fc983417c..0a13bb35f044 100644 --- a/include/linux/mtd/mtd.h +++ b/include/linux/mtd/mtd.h @@ -152,6 +152,15 @@ 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); + /* In blackbox flight recorder like scenarios we want to make successful + writes in interrupt context. panic_write() is only intended to be + called when its known the kernel is about to panic and we need the + 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). */ + + 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, -- cgit v1.2.3