linux-kernel - Re: [PATCH 3B/3 fat] e820: dynamic unknown-xxx names (for DDR3-NvDIMM)

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Date:	Tue, 24 Feb 2015 09:38:17 +0200
From:	Boaz Harrosh <boaz@...xistor.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	Ingo Molnar <mingo@...hat.com>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	X86 ML <x86@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Roger C. Pao" <rcpao.enmotus@...il.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-nvdimm <linux-nvdimm@...ts.01.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 3B/3 fat] e820: dynamic unknown-xxx names (for DDR3-NvDIMM)

On 02/23/2015 05:49 PM, Andy Lutomirski wrote:
> On Mon, Feb 23, 2015 at 4:48 AM, Boaz Harrosh <boaz@...xistor.com> wrote:
>>
>> There are multiple vendors of DDR3 NvDIMMs out in the market today.
>> At various stages of development/production. It is estimated that
>> there are already more the 100ds of thousands chips sold to
>> testers and sites.
>>
>> All the BIOS vendors I know of, tagged these chips at e820 table
>> as type-12 memory.
>>
>> Now the ACPI comity, as far as I know, did not yet define a
>> standard type for NvDIMM. Also, as far as I know any NvDIMM
>> standard will only be defined for DDR4. So DDR3 NvDIMM is
>> probably stuck with this none STD type.
>>
>> I Wish and call the ACPI comity to Define that NvDIMM is type-12.
>> Also for DDR4
>>
>> In this patch I dynamically sprintf names into a static buffer
>> (max two unknown names) of the form "unknown-XXX" where XXX
>> is the type number. This is so we can return static string to
>> caller.
> 
> I prefer the other variant.
> 

Me too

> For Pete's sake, people, defining new e820 types is ludicrous.  It's
> already sort of happened for nvdimms (and I really hope that type 12
> is on its way out), and if it every happens again, we can deal with it
> them.
> 

No, you are wrong sir. What we need to do is define an open system.

e820 is just a table that communicates between the firmware and
the Kernel of the results of the DDR bus scan. Now I bet the same
DDR buses are scanned much differently on other ARCHs. It is only
the forsaken x86 that caries the BIOS baggage,  (for economical reasons
BTW, not technical)
Fine I'm not going to fight that fight, but the BIOS should Just ID
the devices say VENDOR/DEVICE like the PCI does. Or string ID like
USB, or a UUID, and the BAR it is using and get out of the way for real
drivers.

I have seen DDR cards with processors on them, and all systems, and
weird combinations of flashes and RAMs, and batteries, you name it.
It should be easy for new devices to be added, without a single committee
(God how many double letters in this word)

> --Andy
> 

Cheers
Boaz

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