Re: [PATCH v3 1/2] eal/pci: introduce a PCI driver flag

[Thomas Monjalon <thomas@monjalon.net>]

13/06/2017 06:43, Jerin Jacob:
> -----Original Message-----
> > Date: Mon, 12 Jun 2017 18:21:33 +0200
> > From: Thomas Monjalon <thomas@monjalon.net>
> > To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > Cc: dev@dpdk.org, ferruh.yigit@intel.com
> > Subject: Re: [dpdk-dev]  [PATCH v3 1/2] eal/pci: introduce a PCI driver flag
> > 
> > 09/06/2017 12:27, Jerin Jacob:
> > > Some ethdev devices like nicvf thunderx PMD need special treatment for
> > > Secondary queue set(SQS) PCIe VF devices, where, it expects to not unmap
> > > or free the memory without registering the ethdev subsystem.
> > > 
> > > Introducing a new RTE_PCI_DRV_KEEP_MAPPED_RES
> > > PCI driver flag to request PCI subsystem to not unmap the mapped PCI
> > > resources(PCI BAR address) if unsupported device detected.
> > > 
> > > Suggested-by: Ferruh Yigit <ferruh.yigit@intel.com>
> > > Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > [...]
> > > --- a/lib/librte_eal/common/eal_common_pci.c
> > > +++ b/lib/librte_eal/common/eal_common_pci.c
> > > @@ -221,7 +221,12 @@ rte_pci_probe_one_driver(struct rte_pci_driver *dr,
> > >  	ret = dr->probe(dr, dev);
> > >  	if (ret) {
> > >  		dev->driver = NULL;
> > > -		if (dr->drv_flags & RTE_PCI_DRV_NEED_MAPPING)
> > > +		if ((dr->drv_flags & RTE_PCI_DRV_NEED_MAPPING) &&
> > > +			/* Don't unmap if device is unsupported and
> > > +			 * driver needs mapped resources.
> > > +			 */
> > > +			!(ret > 0 &&
> > > +				(dr->drv_flags & RTE_PCI_DRV_KEEP_MAPPED_RES)))
> > >  			rte_pci_unmap_device(dev);
> > >  	}
> > >  
> > > --- a/lib/librte_eal/common/include/rte_pci.h
> > > +++ b/lib/librte_eal/common/include/rte_pci.h
> > > +/** Device driver needs to keep mapped resources if unsupported dev detected */
> > > +#define RTE_PCI_DRV_KEEP_MAPPED_RES 0x0020
> > 
> > If I understand well, you want to map resources but not probe it?
> 
> Yes.
> 
> > Shouldn't it be less hacky to probe it as a (new) null class?
> 
> The Vendor and Class ID is same for those device too so we need to map
> the PCI bar and have access to know the class of device. If you are concerned about
> if it an common code change, My first version was without common code change.
> http://dpdk.org/dev/patchwork/patch/24983/
> 
> Ferruh would like to have flag scheme, I think it make sense for
> PMD maintenance perspective.

Yes

My idea was to have a new class of device interface to reserve those
resources, so the probe function would succeed.
Do you think it would be a good idea?