[PATCH] [MTD] block2mtd.c: Make kernel boot command line arguments work

Ville Herva
2006-07-06T08:25:00Z

Trying to pass kernel command line arguments to block2mtd at boot-time does
not work currently. block2mtd_setup() is called so early that kmalloc()
fails nevermind being able to do open_bdev_excl() (which requires rootfs to
be mounted. This patch only saves the option string at the early boot stage,
and parses them later when block2mtd_init() is called. If open_bdev_excl()
fails, open_by_devnum(name_to_dev_t()) is tried instead, which makes it
possible to initialize the driver before rootfs has been mounted. Also gets
rid of the superfluous parse_name() that only checks if name is longer than
80 chars and copies it to a string that is not kfreed.

With this patch, I can boot statically compiled block2mtd, and mount jffs2
as rootfs (without modules or initrd), with lilo config like this:

root=/dev/mtdblock0
append="rootfstype=jffs2 block2mtd.block2mtd=/dev/hdc2,65536"

(Note that rootfstype=jffs2 is required, since the kernel only tries
filesystems without "nodev" attribute by default, and jffs is "nodev").

From: Ville Herva <vherva@vianova.fi>
Signed-off-by: Ville Herva <vherva@vianova.fi>

--- linux-mtd-GIT/drivers/mtd/devices/block2mtd.c 2006-07-05 23:06:10.000000000 +0300
+++ linux-2.6.17.3/drivers/mtd/devices/block2mtd.c 2006-07-06 11:03:28.000000000 +0300
@@ -18,6 +18,7 @@
#include <linux/mtd/mtd.h>
#include <linux/buffer_head.h>
#include <linux/mutex.h>
+#include <linux/mount.h>

#define VERSION "$Revision: 1.30 $"

@@ -236,6 +237,8 @@ static int _block2mtd_write(struct block
}
return 0;
}
+
+
static int block2mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
size_t *retlen, const u_char *buf)
{
@@ -300,6 +303,17 @@ static struct block2mtd_dev *add_device(
/* Get a handle on the device */
bdev = open_bdev_excl(devname, O_RDWR, NULL);
if (IS_ERR(bdev)) {
+
+ /* We might not have rootfs mounted at this point. Try
+ to resolve the device name by other means. */
+
+ dev_t dev = name_to_dev_t(devname);
+ if (dev != 0) {
+ bdev = open_by_devnum(dev, FMODE_WRITE | FMODE_READ);
+ }
+ }
+
+ if (IS_ERR(bdev)) {
ERROR("error: cannot open device %s", devname);
goto devinit_err;
}
@@ -393,26 +407,6 @@ static int parse_num(size_t *num, const
}

-static int parse_name(char **pname, const char *token, size_t limit)
-{
- size_t len;
- char *name;
-
- len = strlen(token) + 1;
- if (len > limit)
- return -ENOSPC;
-
- name = kmalloc(len, GFP_KERNEL);
- if (!name)
- return -ENOMEM;
-
- strcpy(name, token);
-
- *pname = name;
- return 0;
-}
-
-
static inline void kill_final_newline(char *str)
{
char *newline = strrchr(str, '\n');
@@ -426,14 +420,20 @@ static inline void kill_final_newline(ch
return 0; \
} while (0)

-static int block2mtd_setup(const char *val, struct kernel_param *kp)
+static int block2mtd_init_called = 0;
+static char block2mtd_paramline[80 + 12]; /* 80 for device, 12 for erase size */
+
+
+static int block2mtd_setup2(void)
{
- char buf[80+12]; /* 80 for device, 12 for erase size */
+ char* val = (char*)block2mtd_paramline;
+
+ char buf[80 + 12], *str = buf; /* 80 for device, 12 for erase size */
char *str = buf;
char *token[2];
char *name;
size_t erase_size = PAGE_SIZE;
- int i, ret;
+ int i;

if (strnlen(val, sizeof(buf)) >= sizeof(buf))
parse_err("parameter too long");
@@ -450,16 +450,12 @@ static int block2mtd_setup(const char *v
if (!token[0])
parse_err("no argument");

- ret = parse_name(&name, token[0], 80);
- if (ret == -ENOMEM)
- parse_err("out of memory");
- if (ret == -ENOSPC)
- parse_err("name too long");
- if (ret)
- return 0;
+ name = token[0];
+ if (strlen(name) + 1 > 80)
+ parse_err("device name too long");

if (token[1]) {
- ret = parse_num(&erase_size, token[1]);
+ int ret = parse_num(&erase_size, token[1]);
if (ret) {
kfree(name);
parse_err("illegal erase size");
@@ -472,13 +468,40 @@ static int block2mtd_setup(const char *v
}

+static int block2mtd_setup(const char *val, struct kernel_param *kp)
+{
+ /* Only save the parameters here. We must parse them later:
+ if the param passed from kernel boot command line,
+ block2mtd_setup() is called so early that it is not
+ possible to resolve the device (even kmalloc() fails).
+ Deter that work to block2mtd_setup2(). */
+
+ strlcpy(block2mtd_paramline, val, sizeof(block2mtd_paramline));
+
+ /* If more parameters are later passed in via
+ /sys/module/block2mtd/parameters/block2mtd
+ and block2mtd_init() has already been called,
+ we can parse the argument now. */
+
+ if (block2mtd_init_called)
+ return block2mtd_setup2();
+
+ return 0;
+}
+
+
module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");

static int __init block2mtd_init(void)
{
+ int ret = 0;
INFO("version " VERSION);
- return 0;
+
+ ret = block2mtd_setup2();
+ block2mtd_init_called = 1;
+
+ return ret;
}