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

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Date:	Thu, 3 Mar 2011 14:22:26 -0800
From:	Greg KH <greg@...ah.com>
To:	Matthew Wilcox <willy@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [REVIEW] NVM Express driver

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.

thanks,

greg k-h
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