linux-kernel - Re: [Linux-nvdimm] [PATCH 2/3] x86: add a is_e820

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Date:	Thu, 26 Mar 2015 09:02:20 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Boaz Harrosh <boaz@...xistor.com>
Cc:	Christoph Hellwig <hch@....de>, Ingo Molnar <mingo@...nel.org>,
	Jens Axboe <axboe@...nel.dk>,
	linux-nvdimm <linux-nvdimm@...1.01.org>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [Linux-nvdimm] [PATCH 2/3] x86: add a is_e820_ram() helper

On Thu, Mar 26, 2015 at 8:49 AM, Boaz Harrosh <boaz@...xistor.com> wrote:
> On 03/26/2015 11:34 AM, Christoph Hellwig wrote:
>> +/*
>> + * This is a non-standardized way to represent ADR or NVDIMM regions that
>> + * persist over a reboot.  The kernel will ignore their special capabilities
>> + * unless the CONFIG_X86_PMEM_LEGACY option is set.
>> + *
>> + * Note that older platforms also used 6 for the same type of memory,
>> + * but newer versions switched to 12 as 6 was assigned differently.  Some
>> + * time they will learn..
>> + */
>> +#define E820_PRAM    12
>
> Why the PRAM Name. For one 2/3 of this patch say PMEM the Kconfig
> to enable is _PMEM_, the driver stack that gets loaded is pmem,
> so PRAM is unexpected.
>
> Also I do believe PRAM is not the correct name. Yes NvDIMMs are RAM,
> but there are other not RAM technologies that can be supported exactly
> the same way.
> MEM is a more general name meaning "on the memory bus". I think.
>
> I would love the consistency.

One of nice side of effects of having a "PRAM" name is that we can
later add a UEFI "PMEM" type where the distinction is thsy "PRAM" is
included in the system memory map by default and "PMEM" is analogous
to "IOMEM".  Just a thought...
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