Re: [dpdk-dev] [RFC][PATCH 2/5] pci: allow shared device instances.

[Thomas Monjalon <thomas@monjalon.net>]

10/05/2017 12:11, Radu Nicolau:
> Hi
> 
> 
> On 5/10/2017 10:09 AM, Thomas Monjalon wrote:
> > Hi,
> >
> > 09/05/2017 16:57, Radu Nicolau:
> >> Updated PCI initialization code to allow devices to be shared across multiple PMDs.
> >>
> >> Signed-off-by: Radu Nicolau <radu.nicolau@intel.com>
> > I was waiting the day when we have a device shared
> > by two different interfaces.
> > Note that some Mellanox and Chelsio devices already instantiate
> > two ethdev ports per PCI device.
> >
> > Please explain your idea behind this "shared" flag.
> > What is your exact need?
> 
> Currently for each pci device a look-up into a list of PMDs is 
> performed, and when a match is found the system moves to the next 
> device. Having this flag will allow a PMD to inform the system that 
> there may be more matches, more PMDs that can be used for this 
> particular device.
> There is a difference when comparing to the devices you mentioned above, 
> in this case the PMDs are totally different types, one network and one 
> cryptodev PMD for each IXGBE network card.

Yes I know it is a lack in DPDK.
Linux introduced MultiFunction Device in 2005:
	http://events.linuxfoundation.org/sites/events/files/slides/belloni-mfd-regmap-syscon_0.pdf

> > Do you think it is the best solution?
> 
> We evaluated different approaches and this is what we settled on. It 
> might not be the best, if there are any suggestions of other ways to 
> achieve this I would be thankful.

Please could you explain the other approaches you thought
with pros and cons?

Thanks