linux kernel + ramdisk boot

host > sudo dd if=/dev/zero of=/dev/ram0 bs=1k count=65536
host > sudo mke2fs -vm0 -b 1024 /dev/ram0 65536  // sudo mke2fs -t ext4 -vm0 -b 4096 /dev/ram0 32768
host > sudo tune2fs -c 0 /dev/ram0
host > sudo dd if=/dev/ram0 bs=1k count=65536 | gzip -v9 > ramdisk.gz

========================================================================

host > mkdir mnt
host > gunzip ramdisk.gz
host > sudo mount -o loop ramdisk mnt/
host > ... copy stuff you want to have in ramdisk to mnt...
host > sudo umount mnt
host > gzip -v9 ramdisk

========================================================================

mkimage -A arm -O linux -T ramdisk -n "Initial Ram Disk" -d ramdisk.gz ramdisk.gz.uboot

========================================================================

CONFIG_BLK_DEV_RAM=y

CONFIG_BLK_DEV_RAM_COUNT=4

CONFIG_BLK_DEV_RAM_SIZE=65536

========================================================================

bootargs=root=/dev/ram0 rw

========================================================================

rd_load_image: from [/initrd.image]

========================================================================

static int __init compr_fill(void *buf, unsigned int len)
{
int r = sys_read(crd_infd, buf, len);

printk("%s: initrd len 0x%x, buf %p, return %d\n", __func__, len, buf, r);

if (r < 0)
printk(KERN_ERR "RAMDISK: error while reading compressed data");
else if (r == 0)
printk(KERN_ERR "RAMDISK: EOF while reading compressed data");
return r;
}

========================================================================

static int __init compr_flush(void *window, unsigned int outcnt)
{
static unsigned long total_written;
int written = sys_write(crd_outfd, window, outcnt);

total_written += written;
if (written != outcnt) {
if (decompress_error == 0)
printk(KERN_ERR
       "RAMDISK: incomplete write (%d != %d) total written %lu\n",
       written, outcnt, total_written);
decompress_error = 1;
total_written = 0;
return -1;
}
return outcnt;
}

========================================================================

## initrd_high = 0xffffffff, copy_to_ram = 1
   Loading Ramdisk to 867a8000, end 871ef24d ... OK
   ramdisk load start = 0x867a8000, ramdisk load end = 0x871ef24d

[    0.467428] populate_rootfs: __initramfs_start c07efd08 __initramfs_size 134
[    0.467441] populate_rootfs: initrd_start 0xc67a8000 initrd_end 0xc71ef24d