Re: [PATCH] NVMe: Add a character device for each nvme device

Matthew Wilcox
2012-07-27T20:30:54Z

On Fri, Jul 27, 2012 at 12:21:00PM -0700, Greg KH wrote:
> > > Also, why are you creating your own class? Can't this just be a misc
> > > device? And if you want to create your own class, please don't, use a
> > > bus, as that is what is really happening here, right? We are trying to
> > > move away from using 'struct class' wherever possible (one of these days
> > > we'll just remove it...)
> >
> > What we're trying to achieve here is to create one character device
> > per NVMe controller that gets plugged in. Each NVMe controller is-a
> > PCI function. The reason we're trying to do this is so that we can send
> > commands to the NVMe controller, even when there is no storage present
> > (eg a drive is shipped from the factory with no configured storage).
> >
> > So we have no particular desire to create a new struct class, or struct
> > bus. If we can create a misc device per PCIe function that's bound to our
> > driver, that's great! Can you recommend a driver that does this already?
>
> I don't think there is one, but it shouldn't be that hard to just create
> a 'struct misdevice' for each one of the devices you want to create,
> would it?
>
> But, as you really are a "specific type", a bus_type might be overkill,
> so the original use of device_create() should be fine. Just be sure to
> fix the parent pointer issue, and you should be fine, right?

Works for me. I don't think we're going to have any software that
depends on it being a class or a bus, so it's easy to change later.
All we really care about is /dev/nvmeN being created.