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

[Mark Rutland <mark.rutland@arm.com>]

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:
> > On Fri, Jan 13, 2017 at 06:13:49PM +0900, AKASHI Takahiro wrote:
> > > On Thu, Jan 12, 2017 at 03:39:45PM +0000, Mark Rutland wrote:

> > > > 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.