[dpdk-dev] [PATCH] doc: document the new devargs syntax

[Thomas Monjalon]

23/01/2018 13:46, Yuanhan Liu:
> On Thu, Jan 18, 2018 at 10:46:23AM +0100, Gaëtan Rivet wrote:
> > On Thu, Jan 18, 2018 at 09:46:29AM +0100, Thomas Monjalon wrote:
> > > 18/01/2018 08:35, Yuanhan Liu:
> > > > On Wed, Jan 17, 2018 at 12:34:08PM +0000, Ferruh Yigit wrote:
> > > > > So does it make sense to separate them logically? Perhaps as "device identifier"
> > > > > and "device args".
> > > > 
> > > > Then I think it returns back to the old issue: how could we identify a
> > > > port when the bus id (say BDF for PCI bus) is not enough for identifying
> > > > a port? Such case could happen when a single NIC has 2 ports sharing
> > > > the same BDF. It could also happen with the VF representors that will
> > > > be introduced shortly.
> > > 
> > > Yes, the device matching syntax must include bus category, class category
> > > and driver category. So any device can be identified in future.
> > > 
> > > But I think Ferruh is talking about separating device matching
> > > (which is described in this proposal) and device settings
> > > (which are usually mixed in -w and --vdev options).
> > > I agree there are different things and may be separate.
> > > They could share the same syntax (bus/class/driver) but be separate
> > > with a semicolon:
> > > 	matching;settings
> >
> > Can you give an example?
> 
> Let's take port addition in OVS-DPDK as an example. It happens in 2
> steps:
> - port lookup (if port is already probed)
> - dev attachment (if lookup fails)
> 
> And also let's assume we need probe a ConnectX-3 port. Note that for
> ConnectX-3, there are 2 ports sharing the same PCI addr. Thus, PCI
> BDF is not enough. And let's assume we use another extra property
> "port".
> 
> If the proposal described in this patch is being used, the devarg
> would look like following:
> 
>     bus=pci,id=04:00.0/class=eth,port=0/driver=mlx4,mlx4_arg_A=val,...
> 
> Then "bus=pci,id=04:00.0/class=eth,port=0" will be used for lookup,
> It means we are looking for a port with PCI BDF == 04:00.0 AND
> port == 0 (the first port of the 2 ports).
> 
> Note that in my proposal the driver category is not intended for lookup.
> If any properties needed be looked in the driver category, they would
> probably need be elevated to the class category.

It is not my thought.
I think we should be able to use bus, class and driver properties for lookup.
We can imagine doing a lookup on a driver specific id, which is not
candidate to elevation to the class category.

> If port not found, then the whole string will be used for dev attachment.
> It means we are attaching a port with PCI BDF == 04.00.0 AND
> port == 0 (the 2nd port will not be attached).
> 
> 
> And here is how the devargs would look like if "matching;settings" is
> being used:
> 
>     bus=pci,id=04:00.0/class=eth,port=0;bus=pci,id=04:00.0/class=eth,port=0/driver=mlx4,mlx4_arg_A=val,...
> 
> The part before ";" will be used for lookup and the later part will be
> used for attachment. It should work. It just looks redundant.

It does not have to be redundant.
It can be:
	bus=pci,id=04:00.0/class=eth,port=0;driver=mlx4,mlx4_arg1=settings1,...

Another example, setting the MAC address:
	bus=pci,id=04:00.0/class=eth,port=0;class=eth,mac=00:11:22:33:44:55