[dpdk-dev] [PATCH V2 2/5] Add Intel FPGA BUS Probe Code

[Shreyansh Jain]

Hello Rosen,

On Wed, Mar 21, 2018 at 1:21 PM, 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..e3bcebe 100644
> --- a/lib/librte_eal/common/eal_common_bus.c
> +++ b/lib/librte_eal/common/eal_common_bus.c
> @@ -87,7 +87,7 @@ struct rte_bus_list rte_bus_list =
>  rte_bus_probe(void)
>  {
>         int ret;
> -       struct rte_bus *bus, *vbus = NULL;
> +       struct rte_bus *bus, *vbus = NULL, *ifpga_bus = NULL;
>
>         TAILQ_FOREACH(bus, &rte_bus_list, next) {
>                 if (!strcmp(bus->name, "vdev")) {
> @@ -95,6 +95,11 @@ struct rte_bus_list rte_bus_list =
>                         continue;
>                 }
>
> +               if (!strcmp(bus->name, "ifpga")) {
> +                       ifpga_bus = bus;
> +                       continue;
> +               }
> +
>                 ret = bus->probe();
>                 if (ret)
>                         RTE_LOG(ERR, EAL, "Bus (%s) probe failed.\n",
> @@ -108,6 +113,13 @@ struct rte_bus_list rte_bus_list =
>                                 vbus->name);
>         }
>
> +       if (ifpga_bus) {
> +               ret = ifpga_bus->probe();
> +               if (ret)
> +                       RTE_LOG(ERR, EAL, "Scan for (%s) bus failed.\n",
> +                               ifpga_bus->name);
> +       }
> +

Just like my comment on RFC, I still think this is not the right thing to do.
I understand you want a case where IFPGA bus gets probed only after
PCI bus is probed.
There can be multiple ways. Two of them which I can quickly list
without much deliberation:

1. A framework which can 'defer probing'
   So, a bus can register for defer probe and its
check_if_probe_available() function callback is called through
rte_bus_probe()
   If it returns OK, its probe is called, else it is added to a defer
list which is called once all first register buses are probed.

2. Modify the priority in RTE_REGISTER_BUS and make it as an argument
or a new variant which can take an argument.

It is not ok to change this function specifically for a bus is because
this method is not scalable.

Is there some specific reason you would like to stick to this approach?

[...]

-
Shreyansh