sys 文件 sysfs_create_file negative width in bitfield

   出错代码行如下：

struct my_attribute val_attribute = __ATTR(val, 0666, val_show, val_store);

 解决方法

    是__ATTR宏的权限问题，将上述的0666改为0664，问题迎刃而解。

In file included from ./include/linux/bits.h:22,
                 from ./include/linux/bitops.h:6,
                 from ./include/linux/bitmap.h:8,
                 from ./include/linux/ethtool.h:16,
                 from drivers/net/phy/dp83867.c:7:
./include/linux/build_bug.h:16:51: error: negative width in bit-field ‘<anonymous>’
 #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
                                                   ^
./include/linux/kernel.h:531:3: note: in expansion of macro ‘BUILD_BUG_ON_ZERO’
   BUILD_BUG_ON_ZERO((perms) & 2) +     \
   ^~~~~~~~~~~~~~~~~
./include/linux/sysfs.h:103:12: note: in expansion of macro ‘VERIFY_OCTAL_PERMISSIONS’
    .mode = VERIFY_OCTAL_PERMISSIONS(_mode) },  \
            ^~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/phy/dp83867.c:896:50: note: in expansion of macro ‘__ATTR’
 static struct kobj_attribute dp83867_attribute = __ATTR(dp83867_value, 0666, dp83867_show, dp83867_store);

static int dp83867_value;
static ssize_t dp83867_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
{
   //sprintf(buf, "%d\n", hello_value);
   //MII_BMCR        0x00    /* Basic mode control register */
   //MII_BMSR        0x01    /* Basic mode status register  */
   if (!g_phydev)
    return 0;
   u32 reg  = phy_read(g_phydev,0x00);
   pr_err("BMCR %x \n",reg);
   reg  = phy_read(g_phydev,0x01);
   pr_err("BMSR %x \n",reg);
   reg = phy_read_mmd(g_phydev, DP83867_DEVADDR, DP83867_RGMIICTL);
   pr_err("DP83867_RGMIICTL %x \n",reg);
   reg = phy_read_mmd(g_phydev, DP83867_DEVADDR, DP83867_RGMIIDCTL);
   pr_err("DP83867_RGMIIDCTL %x \n",reg);
   return 0;
}
static ssize_t dp83867_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count)
{
    u32 reg_addr, reg_value;
    sscanf(buf, "%x,%x", &reg_addr, &reg_value);
    pr_err("reg add %x , reg value %x\n",reg_addr, reg_value);
    if(DP83867_RGMIIDCTL == reg_addr || DP83867_RGMIICTL == reg_addr)
    {
    phy_write_mmd(g_phydev, DP83867_DEVADDR, reg_addr, reg_value);
    }
    else if (0x00 ==  reg_addr)
    {
        phy_write(g_phydev,reg_addr,0x00);
    }
    return count;

}
static struct kobj_attribute dp83867_attribute = __ATTR(dp83867_value, 0664, dp83867_show, dp83867_store);
static struct kobject *dp83867_kobj = NULL;
static int dp83867_sys_init(void)
{
    int retval;
    dp83867_kobj = kobject_create_and_add("dp83867", kernel_kobj);
    if (!dp83867_kobj)
        return -ENOMEM;
    retval = sysfs_create_file(dp83867_kobj, &dp83867_attribute.attr);
    if (retval)
        kobject_put(dp83867_kobj);
   return retval;
}
static void dp83867_remove(struct phy_device *phydev)
{
    g_phydev = NULL;
    if (!dp83867_kobj)
            kobject_put(dp83867_kobj);
}

 sprintf和sscanf是对copy_from_user和copy_to_user函数的封装

# ls /sys/kernel/dp83867/

dp83867_value
# ls /sys/kernel/dp83867/dp83867_value 

/sys/kernel/dp83867/dp83867_value

# 
# cat  /sys/kernel/dp83867/dp83867_value 

[  101.698281] BMCR 1140 

[  101.701881] BMSR 796d 

[  101.706221] DP83867_RGMIICTL d3 

[  101.711388] DP83867_RGMIIDCTL a8 



# 
# echo '32,d3' >  /sys/kernel/dp83867/dp83867_value 
# cat  /sys/kernel/dp83867/dp83867_value 

[  211.615714] BMCR 1140 

[  211.619518] BMSR 796d 

[  211.624255] DP83867_RGMIICTL d3 

[  211.630225] DP83867_RGMIIDCTL a8 

# 
# cat  /sys/kernel/dp83867/dp83867_value 
# echo '86,77' >  /sys/kernel/dp83867/dp83867_value 

[  231.221858] reg add 86 , reg value 77

# 
# echo '86,77' >  /sys/kernel/dp83867/dp83867_value 
# cat  /sys/kernel/dp83867/dp83867_value 

[  235.325542] BMCR 1140 

[  235.329554] BMSR 796d 

[  235.334125] DP83867_RGMIICTL d3 

[  235.339593] DP83867_RGMIIDCTL 77 

#