Re: [REVIEW] NVM Express driver

[Andy Lutomirski]

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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