On Thu, Dec 15, 2016 at 03:49:01AM -0800, Greg KH wrote:

On Thu, Dec 15, 2016 at 04:56:18AM -0500, Robert P. J. Day wrote:

quoted

  (Q asked by a colleague, a wee bit vague on details so i'm hoping
i'm describing it correctly, seems like it should be easy to solve.)

  short form of question: what is the standard way of, at boot time,
passing the kernel information to specify that a built-in driver
should *not* be started?

Depends on the subsystem and driver, the only "standard way" is to just
not build the driver into the kernel in the first place and use modules
and load the module from userspace as-needed.

Or, use the device tree that is passed to the kernel by the bootloader
to define the hardware and if the hardware isn't defined, then no driver
will get bound to it.

What about "fixing up" the device tree in U-Boot with functions from
common/fdt_support.(c|h)

Maybe you could use fdt_del_node_and_alias to delete that drivers
device tree node if it is not needed?

Regards,
Clemens