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Subject[PATCH v4] phram: Allow the user to set the erase page size.
Date
From: Patrick O'Grady <patrick@baymotion.com>

Permit the user to specify the erase page size as a parameter.
This solves two problems:

- phram can access images made by mkfs.jffs2. mkfs.jffs2 won't
create images with erase sizes less than 8KiB; many architectures
define PAGE_SIZE as 4KiB.

- Allows more effective use of small capacity devices. JFFS2
needs somewhere between 2 and 5 empty pages for garbage collection;
and for an NVRAM part with only 32KiB of space, a smaller erase page
allows much better utilization in applications where garbage collection
is important.

Signed-off-by: Patrick O'Grady <patrick@baymotion.com>
Reviewed-by: Joern Engel <joern@logfs.org>
Link: https://lore.kernel.org/lkml/CAJ7m5OqYv_=JB9NhHsqBsa8YU0DFRoP7C+W10PY22wonAGJK=A@mail.gmail.com/
[Guohua Zhong: fix token array index out of bounds and update patch for kernel master branch]
Signed-off-by: Guohua Zhong <zhongguohua1@huawei.com>
---
v4:
add three dash before changelog (v1, v2, etc) according to Miquel Raynal

v3: https://lore.kernel.org/lkml/20201207085342.24852-1-zhongguohua1@huawei.com/
update authorship for Patrick O'Grady and remove the reported-by tag for kernel test robot

v2: https://lore.kernel.org/lkml/20201204080821.46868-1-zhongguohua1@huawei.com/
fix build error which is reported by kernel test robot

v1: https://lore.kernel.org/lkml/20201124061053.10812-1-zhongguohua1@huawei.com/
1.fix token array index out of bounds
2.update patch for kernel master branch
---
drivers/mtd/devices/phram.c | 52 +++++++++++++++++++++++++++++----------------
1 file changed, 34 insertions(+), 18 deletions(-)

diff --git a/drivers/mtd/devices/phram.c b/drivers/mtd/devices/phram.c
index 087b5e86d1bf..1729b94b2abf 100644
--- a/drivers/mtd/devices/phram.c
+++ b/drivers/mtd/devices/phram.c
@@ -6,14 +6,14 @@
* Usage:
*
* one commend line parameter per device, each in the form:
- * phram=<name>,<start>,<len>
+ * phram=<name>,<start>,<len>[,<erasesize>]
* <name> may be up to 63 characters.
- * <start> and <len> can be octal, decimal or hexadecimal. If followed
+ * <start>, <len>, and <erasesize> can be octal, decimal or hexadecimal. If followed
* by "ki", "Mi" or "Gi", the numbers will be interpreted as kilo, mega or
- * gigabytes.
+ * gigabytes. <erasesize> is optional and defaults to PAGE_SIZE.
*
* Example:
- * phram=swap,64Mi,128Mi phram=test,900Mi,1Mi
+ * phram=swap,64Mi,128Mi phram=test,900Mi,1Mi,64Ki
*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
@@ -26,6 +26,7 @@
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/mtd/mtd.h>
+#include <asm/div64.h>

struct phram_mtd_list {
struct mtd_info mtd;
@@ -88,7 +89,7 @@ static void unregister_devices(void)
}
}

-static int register_device(char *name, phys_addr_t start, size_t len)
+static int register_device(char *name, phys_addr_t start, size_t len, uint32_t erasesize)
{
struct phram_mtd_list *new;
int ret = -ENOMEM;
@@ -115,7 +116,7 @@ static int register_device(char *name, phys_addr_t start, size_t len)
new->mtd._write = phram_write;
new->mtd.owner = THIS_MODULE;
new->mtd.type = MTD_RAM;
- new->mtd.erasesize = PAGE_SIZE;
+ new->mtd.erasesize = erasesize;
new->mtd.writesize = 1;

ret = -EAGAIN;
@@ -204,22 +205,23 @@ static inline void kill_final_newline(char *str)
static int phram_init_called;
/*
* This shall contain the module parameter if any. It is of the form:
- * - phram=<device>,<address>,<size> for module case
- * - phram.phram=<device>,<address>,<size> for built-in case
- * We leave 64 bytes for the device name, 20 for the address and 20 for the
- * size.
- * Example: phram.phram=rootfs,0xa0000000,512Mi
+ * - phram=<device>,<address>,<size>[,<erasesize>] for module case
+ * - phram.phram=<device>,<address>,<size>[,<erasesize>] for built-in case
+ * We leave 64 bytes for the device name, 20 for the address , 20 for the
+ * size and 20 for the erasesize.
+ * Example: phram.phram=rootfs,0xa0000000,512Mi,65536
*/
-static char phram_paramline[64 + 20 + 20];
+static char phram_paramline[64 + 20 + 20 + 20];
#endif

static int phram_setup(const char *val)
{
- char buf[64 + 20 + 20], *str = buf;
- char *token[3];
+ char buf[64 + 20 + 20 + 20], *str = buf;
+ char *token[4];
char *name;
uint64_t start;
uint64_t len;
+ uint64_t erasesize = PAGE_SIZE;
int i, ret;

if (strnlen(val, sizeof(buf)) >= sizeof(buf))
@@ -228,7 +230,7 @@ static int phram_setup(const char *val)
strcpy(str, val);
kill_final_newline(str);

- for (i = 0; i < 3; i++)
+ for (i = 0; i < 4; i++)
token[i] = strsep(&str, ",");

if (str)
@@ -253,11 +255,25 @@ static int phram_setup(const char *val)
goto error;
}

- ret = register_device(name, start, len);
+ if (token[3]) {
+ ret = parse_num64(&erasesize, token[3]);
+ if (ret) {
+ parse_err("illegal erasesize\n");
+ goto error;
+ }
+ }
+
+ if (len == 0 || erasesize == 0 || erasesize > len
+ || erasesize > UINT_MAX || do_div(len, (uint32_t)erasesize) != 0) {
+ parse_err("illegal erasesize or len\n");
+ goto error;
+ }
+
+ ret = register_device(name, start, len, (uint32_t)erasesize);
if (ret)
goto error;

- pr_info("%s device: %#llx at %#llx\n", name, len, start);
+ pr_info("%s device: %#llx at %#llx for erasesize %#llx\n", name, len, start, erasesize);
return 0;

error:
@@ -298,7 +314,7 @@ static int phram_param_call(const char *val, const struct kernel_param *kp)
}

module_param_call(phram, phram_param_call, NULL, NULL, 0200);
-MODULE_PARM_DESC(phram, "Memory region to map. \"phram=<name>,<start>,<length>\"");
+MODULE_PARM_DESC(phram, "Memory region to map. \"phram=<name>,<start>,<length>[,<erasesize>]\"");


static int __init init_phram(void)
--
2.12.3
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