[dpdk-dev] [RFC 3/4] lib/librte_eal/common: Add Intel FPGA Bus Second Scan, it should be scanned after PCI Bus

[Gaëtan Rivet]

On Tue, Mar 06, 2018 at 10:42:14AM +0000, Xu, Rosen wrote:
> 
> 
> -----Original Message-----
> From: Shreyansh Jain [mailto:shreyansh.jain at nxp.com] 
> Sent: Tuesday, March 06, 2018 14:20
> To: Xu, Rosen <rosen.xu at intel.com>
> Cc: dev at dpdk.org; Doherty, Declan <declan.doherty at intel.com>; Zhang, Tianfei <tianfei.zhang at intel.com>
> Subject: Re: [dpdk-dev] [RFC 3/4] lib/librte_eal/common: Add Intel FPGA Bus Second Scan, it should be scanned after PCI Bus
> 
> On Tue, Mar 6, 2018 at 7:13 AM, Rosen Xu <rosen.xu at intel.com> wrote:
> > Signed-off-by: Rosen Xu <rosen.xu at intel.com>
> > ---
> >  lib/librte_eal/common/eal_common_bus.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/librte_eal/common/eal_common_bus.c 
> > b/lib/librte_eal/common/eal_common_bus.c
> > index 3e022d5..74bfa15 100644
> > --- a/lib/librte_eal/common/eal_common_bus.c
> > +++ b/lib/librte_eal/common/eal_common_bus.c
> > @@ -70,15 +70,27 @@ struct rte_bus_list rte_bus_list =
> >  rte_bus_scan(void)
> >  {
> >         int ret;
> > -       struct rte_bus *bus = NULL;
> > +       struct rte_bus *bus = NULL, *ifpga_bus = NULL;
> >
> >         TAILQ_FOREACH(bus, &rte_bus_list, next) {
> > +               if (!strcmp(bus->name, "ifpga")) {
> > +                       ifpga_bus = bus;
> > +                       continue;
> > +               }
> > +
> >                 ret = bus->scan();
> >                 if (ret)
> >                         RTE_LOG(ERR, EAL, "Scan for (%s) bus failed.\n",
> >                                 bus->name);
> >         }
> >
> > +       if (ifpga_bus) {
> > +               ret = ifpga_bus->scan();
> > +               if (ret)
> > +                       RTE_LOG(ERR, EAL, "Scan for (%s) bus failed.\n",
> > +                               ifpga_bus->name);
> > +       }
> > +
> 
> You are doing this just so that PCI scans are completed *before* ifpga scans?
> Rosen: yes
> Well, I understand that this certainly is an issue that we can't yet define a priority ordering of bus scans.
> 
> But, I think what you are require is a simpler:
> 
> In the file ifpga_bus.c:
> 
> +RTE_REGISTER_BUS(IFPGA_BUS_NAME, rte_ifpga_bus.bus); <== this
> ...
> ...
> #define RTE_REGISTER_BUS(nm, bus) \
> RTE_INIT_PRIO(businitfn_ ##nm, 110); \
> 
> If you define your own version of RTE_REGISTER_BUS with the priority number higher, it would be inserted later in the bus list.
> rte_register_bus doesn't do any inherent ordering.
> This would save the changes you are doing in the lib/librte_eal/common/eal_common_bus.c file.
> 
> But I think there has to be a better provision of defining priority of bus scans - I am sure when new devices come in, there would be possibility of dependencies as in your case.
> Rosen: is the priority scan of bus is implemented?

No, there is no priority set for scanning order.
However, the order in which buses are registered, will modify the order
in which scans are done.

Thus, if you change the priority of your registration, you should be
able to ensure that your scan comes last.

> 
> >         return 0;
> >  }
> >
> > --
> > 1.8.3.1
> >

-- 
Gaëtan Rivet
6WIND