Re: [PATCH 1/4] mdev: Introduce sha1 based mdev alias

[Cornelia Huck]

On Tue, 27 Aug 2019 11:33:54 +0000
Parav Pandit <parav@xxxxxxxxxxxx> wrote:

> > -----Original Message-----
> > From: Cornelia Huck <cohuck@xxxxxxxxxx>
> > Sent: Tuesday, August 27, 2019 4:54 PM
> > To: Parav Pandit <parav@xxxxxxxxxxxx>
> > Cc: alex.williamson@xxxxxxxxxx; Jiri Pirko <jiri@xxxxxxxxxxxx>;
> > kwankhede@xxxxxxxxxx; davem@xxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linux-
> > kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> > Subject: Re: [PATCH 1/4] mdev: Introduce sha1 based mdev alias
> > 
> > On Tue, 27 Aug 2019 11:12:23 +0000
> > Parav Pandit <parav@xxxxxxxxxxxx> wrote:
> >   
> > > > -----Original Message-----
> > > > From: Cornelia Huck <cohuck@xxxxxxxxxx>
> > > > Sent: Tuesday, August 27, 2019 3:54 PM
> > > > To: Parav Pandit <parav@xxxxxxxxxxxx>
> > > > Cc: alex.williamson@xxxxxxxxxx; Jiri Pirko <jiri@xxxxxxxxxxxx>;
> > > > kwankhede@xxxxxxxxxx; davem@xxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx;
> > > > linux- kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> > > > Subject: Re: [PATCH 1/4] mdev: Introduce sha1 based mdev alias
> > > >

> > > > What about:
> > > >
> > > > * @get_alias_length: optional callback to specify length of the alias to  
> > create  
> > > > *                    Returns unsigned integer: length of the alias to be created,
> > > > *                                              0 to not create an alias
> > > >  
> > > Ack.
> > >  
> > > > I also think it might be beneficial to add a device parameter here
> > > > now (rather than later); that seems to be something that makes sense.
> > > >  
> > > Without showing the use, it shouldn't be added.  
> > 
> > It just feels like an omission: Why should the vendor driver only be able to
> > return one value here, without knowing which device it is for?
> > If a driver supports different devices, it may have different requirements for
> > them.
> >   
> Sure. Lets first have this requirement to add it.
> I am against adding this length field itself without an actual vendor use case, which is adding some complexity in code today.
> But it was ok to have length field instead of bool.
> 
> Lets not further add "no-requirement futuristic knobs" which hasn't shown its need yet.
> When a vendor driver needs it, there is nothing prevents such addition.

Frankly, I do not see how it adds complexity; the other callbacks have
device arguments already, and the vendor driver is free to ignore it if
it does not have a use for it. I'd rather add the argument before a
possible future user tries weird hacks to allow multiple values, but
I'll leave the decision to the maintainers.