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

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Message-ID: <55142EC2.8060507@plexistor.com>
Date:	Thu, 26 Mar 2015 18:07:30 +0200
From:	Boaz Harrosh <boaz@...xistor.com>
To:	Dan Williams <dan.j.williams@...el.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 03/26/2015 06:02 PM, Dan Williams wrote:
> 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...
> 

Than lets say E820_PMEM_12, but not PRAM for sure. Also would UEFI be
E820_XXX will it not be a UEFI_PMEM ??

For me I hate RAM because it became to mean a technology, maybe then
the same name as the Kconfig PMEM_LEGACY

Thanks
Boaz

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