Re: [dpdk-dev] [EXT] Re: [PATCH v3 1/6] drivers: add generic API to find PCI extended cap

["Gaëtan Rivet" <grive@u256.net>]

On 26/07/20 19:47 +0000, Manish Chopra wrote:

[...]

> > > diff --git a/lib/librte_pci/rte_pci.h b/lib/librte_pci/rte_pci.h index
> > > a03235da1..fec51e15a 100644
> > > --- a/lib/librte_pci/rte_pci.h
> > > +++ b/lib/librte_pci/rte_pci.h
> > > @@ -22,6 +22,22 @@ extern "C" {
> > >  #include <inttypes.h>
> > >  #include <sys/types.h>
> > >
> > > +
> > > +/*
> > > + * Conventional PCI and PCI-X Mode 1 devices have 256 bytes of
> > > + * configuration space.  PCI-X Mode 2 and PCIe devices have 4096
> > > +bytes of
> > > + * configuration space.
> > > + */
> > > +#define RTE_PCI_CFG_SPACE_SIZE		256
> > > +#define RTE_PCI_CFG_SPACE_EXP_SIZE	4096
> > > +
> > > +/* Extended Capabilities (PCI-X 2.0 and Express) */
> > > +#define RTE_PCI_EXT_CAP_ID(header)	(header & 0x0000ffff)
> > > +#define RTE_PCI_EXT_CAP_NEXT(header)	((header >> 20) & 0xffc)
> > > +
> > > +#define RTE_PCI_EXT_CAP_ID_ERR	0x01	/* Advanced Error Reporting
> > */
> > > +#define RTE_PCI_EXT_CAP_ID_DSN	0x03	/* Device Serial Number */
> > > +
> > 
> > I understand that it is more natural to have those defines in the PCI lib, but I
> > think there is no point in adding them in a separate lib, while the function
> > using those is in the PCI bus.
> > 
> > I think the defines should be put right before the
> > rte_pci_find_next_ext_capability() prototype in
> > drivers/bus/pci/rte_bus_pci.h.
> 
> Hello Gaetan,
> 
> I think these comes in the category of all RTE_PCI_* generic defines (not just use in drivers/bus/pci/),
> Since caller of the API also need to use it, For example, couple of RTE_PCI_* were added in patch #2
> used by qede drivers specifically. rte_pci.h sounds more generic than rte_bus_pci.h hence I thought it
> is the suitable place to consolidate them in there.
> 
> Thanks !!

Reading the additional symbols, particularly about SRIOV capa,
I think you are right, it's probably better to have it all within
rte_pci.h.

To help developers, it would be better to point in the doc that the capability
IDs useable as parameter `cap` can be any from RTE_PCI_EXT_CAP_ID_*,
defined within librte_pci. The dev can then grep it.

One additional thing:

> > > +#define RTE_PCI_CFG_SPACE_SIZE		256
> > > +#define RTE_PCI_CFG_SPACE_EXP_SIZE	4096
> > > +
> > > +/* Extended Capabilities (PCI-X 2.0 and Express) */
> > > +#define RTE_PCI_EXT_CAP_ID(header)	(header & 0x0000ffff)
> > > +#define RTE_PCI_EXT_CAP_NEXT(header)	((header >> 20) & 0xffc)

I think those macros are not useful as part of the public API, they are
only used to implement rte_pci_find_next_ext_capability(). Can you
confirm? If this is correct, I think they should be moved to the
compilation unit implementing rte_pci_find_next_ext_capability().

Regards,
-- 
Gaëtan