RE: Q: Kconfig option VIRT_TO_BUS

H Hartley Sweeten
2012-11-12T23:13:57Z

On Monday, November 12, 2012 11:41 AM, Bjorn Helgaas wrote:
> On Mon, Nov 12, 2012 at 9:18 AM, H Hartley Sweeten wrote:
>> Does anyone know what the Kconfig option VIRT_TO_BUS does?
>> There are a number of "depends on" that option but it does not
>> seem to directly enable any code in the kernel.
>
> virt_to_bus() is a deprecated interface for converting a kernel
> virtual address to a bus address. It's deprecated because it's
> impossible to implement correctly when there are multiple bus address
> spaces, because you don't know which bus address space the caller has
> in mind.

Thanks for the info.

So if a driver does not use virt_to_bus() then the "depends on VIRT_TO_BUS"
is not necessary. Correct?

Thanks,
Hartley