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    Subject[PATCH v3] 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>

    v3:
    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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