linux-kernel - Re: [REVIEW] NVM Express driver

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Message-ID: <4D704DAB.9080100@mit.edu>
Date:	Thu, 03 Mar 2011 21:25:47 -0500
From:	Andy Lutomirski <luto@....EDU>
To:	Greg KH <greg@...ah.com>
CC:	Matthew Wilcox <willy@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [REVIEW] NVM Express driver

On 03/03/2011 05:22 PM, Greg KH wrote:
> On Thu, Mar 03, 2011 at 05:07:35PM -0500, Matthew Wilcox wrote:
>> On Thu, Mar 03, 2011 at 01:51:55PM -0800, Greg KH wrote:
>>> Heh, no, well, submit_io should just go through the block layer and not
>>> be a separate ioctl, right?
>>
>> Just like with SG_IO, there are reasons to do I/Os without going through
>> the block layer.
>
> Ok, that makes sense.
>
>>>> There's a bit of an impedence mismatch there.  Think of this as
>>>> being drive firmware instead of controller firmware.  This isn't for
>>>> request_firmware() kind of uses, it's for some admin tool to come along
>>>> and tell the drive "Oh, here's some new firmware for you".
>>>
>>> That's fine, request_firmware will work wonderfully for that.
>>
>> How would the driver know that it should call request_firmware()?
>> Do it every 60 seconds in case somebody's downloaded some new firmware?
>
> Ick, no, just use the function provided that lets you create a firmware
> request and be notified when it is written to,
> request_firmware_nowait().  That is what it is there for.
>
>>>> If you look at the spec [1], you'll see there are a number of firmware
>>>> slots in the device, and it's up to the managability utility to decide
>>>> which one to replace or activate.  I dno't think you want to pull all
>>>> that gnarly decision making code into the kernel, do you?
>>>>
>>>> [1] http://download.intel.com/standards/nvmhci/NVM_Express_1_0_Gold.pdf
>>>
>>> No, just export multiple "slots" as firmware devices ready to be filled
>>> in by userspace whenever it wants/needs to.  The management utility can
>>> just dump the firmware to those sysfs files when it determines it needs
>>> to update the firmware, no decision making in the kernel at all.
>>
>> OK ... glad we decided to limit the number of slots.  I still don't see
>> (in Documentation/firmware_class/README) how this works for user-initiated
>> firmware updates rather than kernel-initiated.
>
> I didn't even realize we had a firmware README file...
>
> Anyway, just use request_firmware_nowait(), you will be fine.
>

Unless I'm misunderstanding the spec, this is for *nonvolatile* firmware 
updates.  So if I have two of these devices and I stick a firmware file 
into /lib/firmware, should it update both devices?

Shouldn't reflashing the device firmware be something that the users 
asks for by something a little more specific than just creating a file? 
  (In any case, creating /lib/firmware/nvmhci-3 to flash slot 3 seems 
rather silly.)

--Andy
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