If codec->control_data is not provided, the following crash happens:

Unable to handle kernel NULL pointer dereference at virtual address 00000078
pgd = 80004000
[00000078] *pgd=00000000
Internal error: Oops: 5 [#1] SMP ARM
Modules linked in:
CPU: 0    Tainted: G        W     (3.5.0-next-20120725+ #1263)
PC is at regmap_read+0x18/0x64
LR is at hw_read+0x50/0x98
pc : [<802bcd90>]    lr : [<803cad18>]    psr: 60000013
...
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>