[dpdk-dev] [PATCH 7/9] bus: add helper to find a bus from a device name

[Gaëtan Rivet]

On Thu, Jun 08, 2017 at 01:40:46PM +0200, Jan Blunck wrote:
> On Thu, Jun 8, 2017 at 1:36 PM, Gaëtan Rivet <gaetan.rivet at 6wind.com> wrote:
> > On Thu, Jun 08, 2017 at 12:45:17PM +0200, Jan Blunck wrote:
> >> On Wed, Jun 7, 2017 at 10:03 PM, Gaëtan Rivet <gaetan.rivet at 6wind.com> wrote:
> >> > On Wed, Jun 07, 2017 at 07:28:07PM +0200, Jan Blunck wrote:
> >> >> On Wed, May 24, 2017 at 5:12 PM, Gaetan Rivet <gaetan.rivet at 6wind.com> wrote:
> >> >> > Find which bus should be able to parse this device name into an internal
> >> >> > device representation.
> >> >> >
> >> >>
> >> >> No, please don't add this. One should know to what bus a device
> >> >> belongs to before plugging it. Artificially encoding the parent bus
> >> >> into the device name is not the right thing to do. Please keep those
> >> >> things separate.
> >> >>
> >> >
> >>
> >> When plugging a device the users know about:
> >> - bus name
> >> - device name
> >>
> >> Its not the case that the users invent the device names out of thin
> >> air. The EAL shouldn't codify what the users of the EAL already know
> >> about.
> >>
> >>
> >
> > Yes, but in that case the user is forced to explicitly name the bus used
> > for a device.
> >
> > I think it might be sufficient to have this as a private function to the
> > EAL, as it is currently only used within the rte_devargs parsing.
> > Applications could use this helper to recognize a bus from a device
> > name, but this is contrived.
> >
> 
> Just remove it. Putting the knowledge of what bus a device name could
> be for into code has failed before (e.g. biosdevname etc.). If the
> application doesn't know what bus the device is living on we have a
> different problem.
> 

This means that devices will be declared as follows:

  -w PCI:00:02.0 -w virtual:net_ring0

Without a way to keep the legacy behavior.
Do you agree with it?

> >> > The EAL has no way to know this currently. As you noted, it has to know
> >> > onto which bus a device belongs before plugging it.
> >> >
> >> >> > Signed-off-by: Gaetan Rivet <gaetan.rivet at 6wind.com>
> >> >> > ---
> >> >> >  lib/librte_eal/bsdapp/eal/rte_eal_version.map   |  1 +
> >> >> >  lib/librte_eal/common/eal_common_bus.c          | 15 +++++++++++++++
> >> >> >  lib/librte_eal/common/include/rte_bus.h         | 12 ++++++++++++
> >> >> >  lib/librte_eal/linuxapp/eal/rte_eal_version.map |  1 +
> >> >> >  4 files changed, 29 insertions(+)
> >> >> >
> >> >> > diff --git a/lib/librte_eal/bsdapp/eal/rte_eal_version.map b/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> >> >> > index 3517d74..04fa882 100644
> >> >> > --- a/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> >> >> > +++ b/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> >> >> > @@ -202,5 +202,6 @@ DPDK_17.08 {
> >> >> >         global:
> >> >> >
> >> >> >         rte_bus_from_name;
> >> >> > +       rte_bus_from_dev;
> >> >> >
> >> >> >  } DPDK_17.05;
> >> >> > diff --git a/lib/librte_eal/common/eal_common_bus.c b/lib/librte_eal/common/eal_common_bus.c
> >> >> > index 7977190..08fff60 100644
> >> >> > --- a/lib/librte_eal/common/eal_common_bus.c
> >> >> > +++ b/lib/librte_eal/common/eal_common_bus.c
> >> >> > @@ -242,3 +242,18 @@ rte_bus_from_name(const char *str)
> >> >> >                 return NULL;
> >> >> >         return rte_bus_find(bus_cmp_name, str);
> >> >> >  }
> >> >> > +
> >> >> > +static int
> >> >> > +bus_can_parse(const struct rte_bus *bus, const void *_name)
> >> >> > +{
> >> >> > +       const char *name = _name;
> >> >> > +
> >> >> > +       return (bus->parse && !bus->parse(name, NULL));
> >> >> > +}
> >> >> > +
> >> >> > +/* find a bus capable of parsing a device description */
> >> >> > +struct rte_bus *
> >> >> > +rte_bus_from_dev(const char *str)
> >> >> > +{
> >> >> > +       return rte_bus_find(bus_can_parse, str);
> >> >> > +}
> >> >> > diff --git a/lib/librte_eal/common/include/rte_bus.h b/lib/librte_eal/common/include/rte_bus.h
> >> >> > index 5b87ac4..0b48e66 100644
> >> >> > --- a/lib/librte_eal/common/include/rte_bus.h
> >> >> > +++ b/lib/librte_eal/common/include/rte_bus.h
> >> >> > @@ -251,6 +251,18 @@ struct rte_bus *rte_bus_find_by_device(const struct rte_device *dev);
> >> >> >  struct rte_bus *rte_bus_from_name(const char *str);
> >> >> >
> >> >> >  /**
> >> >> > + * Find a bus capable of identifying a device.
> >> >> > + *
> >> >> > + * @param str
> >> >> > + *   A device identifier (PCI address, virtual PMD name, ...).
> >> >> > + *
> >> >> > + * @return
> >> >> > + *   A valid bus structure if found.
> >> >> > + *   NULL if no bus is able to parse this device.
> >> >> > + */
> >> >> > +struct rte_bus *rte_bus_from_dev(const char *str);
> >> >> > +
> >> >> > +/**
> >> >> >   * Helper for Bus registration.
> >> >> >   * The constructor has higher priority than PMD constructors.
> >> >> >   */
> >> >> > diff --git a/lib/librte_eal/linuxapp/eal/rte_eal_version.map b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> >> >> > index 6607acc..a5127d6 100644
> >> >> > --- a/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> >> >> > +++ b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> >> >> > @@ -206,5 +206,6 @@ DPDK_17.08 {
> >> >> >         global:
> >> >> >
> >> >> >         rte_bus_from_name;
> >> >> > +       rte_bus_from_dev;
> >> >> >
> >> >> >  } DPDK_17.05;
> >> >> > --
> >> >> > 2.1.4
> >> >> >
> >> >
> >> > --
> >> > Gaėtan Rivet
> >> > 6WIND
> >
> > --
> > Gaëtan Rivet
> > 6WIND

-- 
Gaëtan Rivet
6WIND