[dpdk-dev] [PATCH v5 04/12] eal: integrate bus scan and probe with EAL

[Shreyansh Jain]

On Wednesday 04 January 2017 03:16 AM, Thomas Monjalon wrote:
> 2016-12-26 18:53, Shreyansh Jain:
>> --- a/lib/librte_eal/linuxapp/eal/eal.c
>> +++ b/lib/librte_eal/linuxapp/eal/eal.c
>> @@ -844,6 +845,9 @@ rte_eal_init(int argc, char **argv)
>>         if (rte_eal_intr_init() < 0)
>>                 rte_panic("Cannot init interrupt-handling thread\n");
>>
>> +       if (rte_eal_bus_scan())
>> +               rte_panic("Cannot scan the buses for devices\n");
>
> Yes, definitely. Just one scan functions which scan registered bus.
>
>> @@ -884,6 +888,9 @@ rte_eal_init(int argc, char **argv)
>>         if (rte_eal_pci_probe())
>>                 rte_panic("Cannot probe PCI\n");
>>
>> +       if (rte_eal_bus_probe())
>> +               rte_panic("Cannot probe devices\n");
>> +
>>         if (rte_eal_dev_init() < 0)
>>                 rte_panic("Cannot init pmd devices\n");
>
> What is the benefit of initializing (probe) a device outside of the scan?
> Currently, it is done in two steps, so you are keeping the same behaviour.

Yes, only for compatibility to existing model of two-step process.
Ideally, only a single step is enough (init->probe).

During the discussion in [1] also this point was raised - at that time
for VDEV and applicability to PCI.

[1] http://dpdk.org/ml/archives/dev/2016-December/051306.html

If you want, I can merge these two. I postponed it because 1) it is an
independent change and should really impact bus and 2) I was not sure
of dependency of init *before* pthread_create for all workers.

>
> I imagine a model where the scan function decide to initialize the
> device and can require some help from a callback to make this decision.
> So the whitelist/blacklist policy can be implemented with callbacks at
> the scan level and possibly the responsibility of the application.
> Note that the callback model would be a change for a next release.
>

Agree. But, that is not really part of Bus patches - isn't it? Or, you
want to change that with this series?