[dpdk-dev] [PATCH v7 2/9] eal: introduce RTE common initialization level

[David Marchand]

On Mon, Jul 20, 2020 at 9:30 PM Ori Kam <orika at mellanox.com> wrote:
> > net and vdpa code expect the common code being initialised.
> > It is a dependency internal to mlx5 drivers, I see nothing generic.
> >
> First the idea was to declare a new bus not a PMD.
> The issue is not from common code but from loading more than one
> device on the same PCI.
> So the logic is Mellanox PMD are registering to the new bus, the new bus
> register to the PCI one.

- Is there a problem with the snippet I sent yesterday that removes
the COMMON priority?


- Currently in the main branch, the net/mlx5 driver is a pci driver
registered to the pci bus driver.
This registration happens in a constructor which puts the net/mlx5 pci
driver struct (with a populated id map) into the pci driver list.
Later (out of constructor context), a probe on the pci bus uses this
driver list.


A new pci driver is introduced by Mellanox to solve resources
dispatching between mlx5 drivers.
I'd rather not call this new pci driver a bus, it is not registered as
such (no rte_bus object) => no reason its constructor should be called
from the RTE_PRIO_BUS priority.

This driver not being a bus, I would not put it in drivers/bus/,
rather in the common code.
If there is a build dependency issue with the pci bus driver, you can
probably use the trick from qat
(https://git.dpdk.org/dpdk/tree/drivers/Makefile#n17) and write an
explicit dependency in drivers/Makefile.
meson should be just fine.


net/mlx5 and vdpa/mlx5 are not classes => no reason their constructor
should be called from the RTE_PRIO_CLASS priority.
The only classes we have are ethdev and vdpa.


The new pci driver simply serves as a proxy for mlx5 net and vdpa drivers.
>From what I see, the new pci driver constructs its pci device id
map/drv_flags when registering to the pci bus driver based on what
mlx5 net and vdpa drivers registered before.
This is where a dependency was created.

You can move the id_table/drv_flags construction from
RTE_INIT(mlx5_bus_pci) to rte_mlx5_pci_register() itself.
This way, net/mlx5 and vdpa/mlx5 will pass their id_map to the mlx5
pci driver whether it is registered to the pci bus or not yet.


-- 
David Marchand