Re: [PATCH v29 9/9] Documentation: dt: chosen properties for arm64 kdump

On Mon, Jan 16, 2017 at 05:25:07PM +0900, AKASHI Takahiro wrote:

On Fri, Jan 13, 2017 at 11:17:56AM +0000, Mark Rutland wrote:

quoted

On Fri, Jan 13, 2017 at 06:13:49PM +0900, AKASHI Takahiro wrote:

quoted

On Thu, Jan 12, 2017 at 03:39:45PM +0000, Mark Rutland wrote:

quoted

quoted

quoted

arm64 we should either ensure that /proc/iomem is consistently usable
(and have userspace consistently use it), or we should expose a new file
specifically to expose this information.

The thing that I had in my mind when adding this property is that
/proc/iomem would be obsolete in the future, then we should have
an alternative in hand.

Ok.

My disagreement is with using the DT as a channel to convey information
from the kernel to userspace.

I'm more than happy for a new file or other mechanism to express this
information. For example, we could add
/sys/kernel/kexec_crash_{base,size} or similar.

It may make sense because /sys/kernel/kexec_crash_size already exists,
so why not kexec_crash_base?
My concern, however, is that this kind of interface might prevent us from
allowing multiple regions to be reserved for crash dump kernel in the future.
(There is an assumption that we have only one region at least on arm64 though.)

Ok.

If we need to handle that, we should also update the description of
linux,usable-memory-range to allow multiple entries (and probably
s/range/ranges).

Thanks,
Mark.