[U-Boot] confused by "upgrade_available=0\0" in include/configs/taurus.h

[Robert P. J. Day]

  never embarrassed to make a fool of myself, i have to admit that,
while crawling through examples of u-boot boards that define dual
partitions, i am confused by the following in
include/configs/taurus.h (only some lines reproduced):

  #define CONFIG_BOOTARGS_AXM                                           \
        "\0"    \
        "flash_nfs=run nand_kernel;run nfsargs;run addip;upgrade_available;"\
        "flash_self=run nand_kernel;run setbootargs;upgrade_available;" \
        "flash_self_test=run nand_kernel;run setbootargs addtest; "     \
        "upgrade_available;bootm ${kernel_ram};reset\0"
        "net_nfs=run boot_file;tftp ${kernel_ram} ${bootfile};"         \
        "run nfsargs;run addip;upgrade_available;bootm "                \
                "${kernel_ram};reset\0"                                 \

        ... snip ...

        "upgrade_available=0\0"
  #endif

what does it mean for "upgrade_available;" to be in the middle of some
of those command definitions? it's just a variable, what does it
represent? am i just clueless for never having noticed this sort of
thing before?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================