Re: [PATCH 04/13] eal: introduce driver type

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue, 20 Dec 2016 14:00:55 +0100
Jan Blunck <jblunck@infradead.org> wrote:

> On Mon, Dec 19, 2016 at 10:59 PM, Stephen Hemminger
> <stephen@networkplumber.org> wrote:
> > Since multiple buses and device types need to be supported.
> > Provide type field in driver.
> > ---
> >  lib/librte_eal/common/include/rte_dev.h  | 15 ++++++++++++---
> >  lib/librte_eal/common/include/rte_pci.h  |  1 +
> >  lib/librte_eal/common/include/rte_vdev.h |  1 +
> >  3 files changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/librte_eal/common/include/rte_dev.h b/lib/librte_eal/common/include/rte_dev.h
> > index e5471a22..3f4e26e6 100644
> > --- a/lib/librte_eal/common/include/rte_dev.h
> > +++ b/lib/librte_eal/common/include/rte_dev.h
> > @@ -144,12 +144,21 @@ void rte_eal_device_insert(struct rte_device *dev);
> >  void rte_eal_device_remove(struct rte_device *dev);
> >
> >  /**
> > + * Type of device driver
> > + */
> > +enum rte_driver_type {
> > +       PMD_VIRTUAL,
> > +       PMD_PCI,
> > +};
> > +
> > +/**
> >   * A structure describing a device driver.
> >   */
> >  struct rte_driver {
> >         TAILQ_ENTRY(rte_driver) next;  /**< Next in list. */
> > -       const char *name;                   /**< Driver name. */
> > -       const char *alias;              /**< Driver alias. */
> > +       const char *name;              /**< Driver name. */
> > +       const char *alias;             /**< Driver alias. */
> > +       enum rte_driver_type type;     /**< Driver type. */
> >  };  
> 
> I wonder who is the user of the type. It can't be the driver itself
> because it must be aware of what kind of low-level interface it
> serves. So this seems to be a helper to allow users of rte_driver to
> upcast to the object that embeds the rte_driver at runtime. I don't
> believe that this is a good interface because it often leads to ugly
> and error prone code.

The thing I ran into was the test code. The testpmd (and related code) is an
example of how some code might want to use dev_info_get to find out about a device
then take some action based on the driver type.  Testpmd has code that manipulates
PCI registers. Right now it is broken when run on virtual devices.