arm - How to add customised ATAG variable in U-Boot and Linux kernel? -

i want add customized atag variable in u-boot , linux kernel.
how can achieve this?
there procedure add atag variable in u-boot , linux?

follow procedure ,

to achieve goal, there're 2 parts need modified. 1 u-boot, , other 1 linux kernel.

    1.    u-boot changes required :          a.     make sure  config_cmdline_tag/config_setup_memory_tags/config_initrd_tag defined in project definition header file ( u-boot/include/configs/am335x_evm.h ), ,  can add our own tag here, eg. config_custom_tag.          b.     add structure definition wanna append w/ atag in u-boot/include/asm-arm/setup.h, eg.              #define atag_custom 0x5441000a             struct tag_custom{             unsigned char mac_addr[6];             };          c.    add struct @ tail of "u"...              struct tag {                     struct tag_header hdr;                     union {                     struct tag_core         core;                     struct tag_mem32        mem;                     struct tag_videotext    videotext;                     struct tag_ramdisk      ramdisk;                     struct tag_initrd       initrd;                     struct tag_serialnr     serialnr;                     struct tag_revision     revision;                     struct tag_videolfb     videolfb;                     struct tag_cmdline      cmdline;                      /*                      * acorn specific                      */                     struct tag_acorn        acorn;                      /*                      * dc21285 specific                      */                     struct tag_memclk       memclk;                      /****** infotech custom tag ********/                     struct tag_custom custom;                     } u;                 };          d.    add implementation code in lib_arm/bootm.c:              static void setup_custom_tag(bd_t *bd);              static void setup_custom_tag(bd_t *bd) {                 params->hdr.tag = atag_custom;                    params->hdr.size = tag_size (tag_macaddr);                 params->u.custom.cmd =0;                 params = tag_next (params);             }          e.    add "#ifdef config_custom_tag / #endif" @ every place change code.          f.    done of u-boot modification.  2. linux changes required:          a.    add parse tag code in linux/arch/arm/kernel/setup.c:              int cmd;             static int __init parse_tag_custom(const struct tag *tag){                     printk("u.custom.cmd=%d\n",tag->u.custom.cmd);                 return 0;             }              __tagtable(atag_macaddr, parse_tag_custom);          b. add structure declaration u-boot did in linux/include/asm-arm/setup.h:              #define atag_macaddr 0x5441000a             struct tag_custom {                 int cmd;             };          c. add struct @ tail of "u"...              struct tag {                 struct tag_header hdr;                union {                     struct tag_core         core;                  struct tag_mem32        mem;                 struct tag_videotext    videotext;                 struct tag_ramdisk      ramdisk;                 struct tag_initrd       initrd;                 struct tag_serialnr     serialnr;                 struct tag_revision     revision;                 struct tag_videolfb     videolfb;                 struct tag_cmdline      cmdline;                  /*                  * acorn specific                  */                 struct tag_acorn        acorn;                  /*                  * dc21285 specific                  */                 struct tag_memclk       memclk;                  /* add infotech custom tag */                  struct tag_custom      custom;                 } u;             };          d. done w/ kernel parts.