/* Step1 we find offset 137 seems to be unused */
(none):/mnt/ramfs/root# ./spi_read 137
A:buff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff: [151(decimal)]

/* Step 2 write 7 bytes to offset 137 starting at value=2 */
(none):/mnt/ramfs/root# ./spi_write 137 7 2

/* Step3 verify write */
(none):/mnt/ramfs/root# ./spi_read 137
A:buff:02:03:04:05:06:07:08:ff:ff:ff:ff:ff:ff:ff: [151(decimal)]

/* Step 4 One by One restire 8 bytes to 0xff */
(none):/mnt/ramfs/root# ./spi_write 137 1 255
(none):/mnt/ramfs/root# ./spi_write 138 1 255
(none):/mnt/ramfs/root# ./spi_write 139 1 255
(none):/mnt/ramfs/root# ./spi_write 140 1 255
(none):/mnt/ramfs/root# ./spi_write 141 1 255
(none):/mnt/ramfs/root# ./spi_write 142 1 255
(none):/mnt/ramfs/root# ./spi_write 143 1 255

/* Step 5 verify with read */
(none):/mnt/ramfs/root# ./spi_read 137
A:buff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff: [151(decimal)]

Note: For block writes it is safer to use smaller numbers such as 7.
I found writes were unreliable with counts of 8 and 9 even though the
Atmel was receiving the correct byte sequence.