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SubjectRe: [Linux-nvdimm] another pmem variant
On Mon, Apr 13, 2015 at 2:01 AM, Greg KH <> wrote:
> On Wed, Mar 25, 2015 at 10:00:26AM -0700, Dan Williams wrote:
>> On Wed, Mar 25, 2015 at 9:44 AM, Christoph Hellwig <> wrote:
>> > On Wed, Mar 25, 2015 at 09:33:52AM -0700, Dan Williams wrote:
>> >> This is mostly ok and does not collide too much with the upcoming ACPI
>> >> mechanism for this stuff. I do worry that the new
>> >> "memmap=nn[KMG]!ss[KMG]" kernel command line option will only be
>> >> relevant for at most one kernel cycle given the imminent publication
>> >> of the spec that unblocks our release.
>> >
>> > I don't think we can just get rid of it as legacy systems won't be
>> > upgraded to the new discovery mechanism. Or do you mean you plan to
>> > introduce a better override on the command line? In that case speak
>> > up now!
>> The kernel command line would simply be the standard/existing memmap=
>> to reserve a memory range. Then, when the platform device loads, it
>> does a request_firmware() to inject a binary table that further carves
>> memory into ranges to which the pmem driver attaches. No need for the
>> legacy system BIOS to be upgraded to the "new way".
> Um, what parses that "binary table"? The kernel better not be doing
> that, as that's not what the firmware interface is for. The firmware
> interface is for "pass through" only directly to hardware.

I had been using it as a generic/device-model-integrated way to do
what amounts to ACPI table injection [1]. But, now that the new
memmap= command line is upstream, most of the benefits of this
approach are moot and no longer outweigh the downsides [2]. Consider
it tabled.


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