[dpdk-dev] [PATCH 0/9] rte_bus parse API

[Gaëtan Rivet]

On Wed, Jun 07, 2017 at 07:22:05PM +0200, Jan Blunck wrote:
> On Wed, May 24, 2017 at 5:12 PM, Gaetan Rivet <gaetan.rivet at 6wind.com> wrote:
> > Following the evolutions announced in [1], here is the first part of
> > the rte_devargs rework planned for 17.08. The rationale has been partially
> > explained in [2].
> >
> > This first part covers the introduction of the necessary facilities in
> > rte_bus to allow for generic device parsing. This API is implemented for
> > the virtual and PCI buses. Additionally, this rte_bus evolution is being
> > used within rte_devargs to characterize a device type by its bus.
> > This work is the first of two parts to reduce the dependency of the EAL
> > upon specific bus implementations.
> >
> > Two public functions are added to rte_bus to help bus recognition:
> >
> > - rte_bus_from_name
> > - rte_bus_from_dev
> >
> > These functions are made public because the bus handle within devargs
> > becomes the generic device type. Recognizing device types is useful for
> > buses and PMDs alike.
> > The modified rte_devargs parsing allows declaring on the EAL command line
> > explicit buses to handle a device. The format is as follow:
> >
> >   --vdev="virtual:net_ring0" --vdev="net_tap0,iface=tap0"
> >   -w PCI:00:02.0 -w 00:03.0
> >
> 
> I don't see the point of doing this. The --vdev parameter implicitly
> defines the bus by its name (--vdev aka virtual device).
> 
> Why don't you add a commandline "--dev" parameter that supports a
> "bus=" devarg? You would need to clarify what that means for other
> busses than the virtual one. Is the bus switched into whitelist mode
> by that?
> 
> 

We cannot keep the current -w, -b and --vdev parameter. Those are
processed by the EAL, and use specifics from the virtual and PCI buses.

The rte_devargs rework has been to make the same functionality generic
to all rte_bus. As seen quickly in [2], rte_devargs has two functions:

* Validating a device declaration
* Keeping the relevant device info until it has been processed.

Both functionalities have been genericized. This results in all parameters
being able to be used with all types of devices. This is inherent to the
EAL becoming bus-agnostic.

Now, it is absolutely possible to rename for example -w as --dev, as it
is the expected behavior from users. This however should be discussed by
the community, last time I talked about the possibility of switching the
default of the PCI bus to whitelist mode the community wasn't all that
enthused by the prospect.

Finally, I do not like the idea of a special devarg just for declaring
explicitly buses for devices. The bus is not a device modifier, nor is
it a driver parameter. The bus is a way to define the location of the
device on the system. Adding a special "bus=" devargs means having some
preprocessing done on devargs upon rte_devargs allocation. This was
already abused by the bonding PMD with the driver= parameter. I do not
support this and did not want to repeat it. Passing down the device args
is a simple process and we should keep it as simple as possible.

I know you do not like having the bus as part of the device name.
As a compromise, I made the current system flexible and allowed the legacy
device definition to be kept.

However with a purely generic process, it is necessary to at least offer
the possibility to the user to explicitly use a bus, as nothing prevents
conflicting device names from existing.

> > [2]: http://dpdk.org/ml/archives/dev/2017-May/065670.html

> > This explicit bus designation is optional; no evolution is currently
> > forced on users to migrate to this new format. The separating character is
> > arbitrary and can be any character illegal within a bus name.
> > Subsequently, what is allowed within a bus name has been formally
> > defined and is now enforced.
> >
> > [1]: http://dpdk.org/ml/archives/dev/2017-May/065634.html
> > [2]: http://dpdk.org/ml/archives/dev/2017-May/065670.html
> >
> > This patchset depends on:
> >
> > bus: attach / detach API
> > http://dpdk.org/ml/archives/dev/2017-May/066330.html
> > http://dpdk.org/dev/patchwork/patch/24489/
> >
> > Gaetan Rivet (9):
> >   bus: fix bus name registration
> >   bus: verify bus name on registration
> >   bus: introduce parsing functionality
> >   vdev: implement parse bus operation
> >   pci: implement parse bus operation
> >   bus: add helper to find bus from a name
> >   bus: add helper to find a bus from a device name
> >   vdev: expose bus name
> >   devargs: parse bus info
> >
> >  lib/librte_eal/bsdapp/eal/rte_eal_version.map   |  8 +++
> >  lib/librte_eal/common/eal_common_bus.c          | 47 +++++++++++++++++
> >  lib/librte_eal/common/eal_common_devargs.c      | 17 +++++-
> >  lib/librte_eal/common/eal_common_pci.c          | 19 +++++++
> >  lib/librte_eal/common/eal_common_vdev.c         | 70 ++++++++++++++-----------
> >  lib/librte_eal/common/eal_private.h             | 16 ++++++
> >  lib/librte_eal/common/include/rte_bus.h         | 49 ++++++++++++++++-
> >  lib/librte_eal/common/include/rte_devargs.h     |  3 ++
> >  lib/librte_eal/common/include/rte_vdev.h        |  2 +
> >  lib/librte_eal/linuxapp/eal/rte_eal_version.map |  8 +++
> >  10 files changed, 205 insertions(+), 34 deletions(-)
> >
> > --
> > 2.1.4
> >

-- 
Gaëtan Rivet
6WIND