It fails with the following error messages:
CC drivers/block/rd.o
drivers/block/rd.c:67: error: `CONFIG_BLK_DEV_RAM_COUNT' undeclared here (not in a function)
drivers/block/rd.c:68: error: `CONFIG_BLK_DEV_RAM_COUNT' undeclared here (not in a function)
drivers/block/rd.c:69: error: `CONFIG_BLK_DEV_RAM_COUNT' undeclared here (not in a function)
drivers/block/rd.c: In function `rd_cleanup':
drivers/block/rd.c:403: error: `CONFIG_BLK_DEV_RAM_COUNT' undeclared (first use in this function)
drivers/block/rd.c:403: error: (Each undeclared identifier is reported only once
drivers/block/rd.c:403: error: for each function it appears in.)
drivers/block/rd.c: In function `rd_init':
drivers/block/rd.c:433: error: `CONFIG_BLK_DEV_RAM_COUNT' undeclared (first use in this function)
drivers/block/rd.c: At top level:
drivers/block/rd.c:67: error: storage size of `rd_disks' isn't known
drivers/block/rd.c:68: error: storage size of `rd_bdev' isn't known
drivers/block/rd.c:69: error: storage size of `rd_queue' isn't known
drivers/block/rd.c:67: warning: `rd_disks' defined but not used
drivers/block/rd.c:68: warning: `rd_bdev' defined but not used
drivers/block/rd.c:69: warning: `rd_queue' defined but not used
make[2]: *** [drivers/block/rd.o] Error 1
make[1]: *** [drivers/block] Error 2
make: *** [drivers] Error 2