Re: [dpdk-dev] [PATCH v3 1/3] drivers/bus: move driver assignment to end of probing

[Thomas Monjalon <thomas@monjalon.net>]

11/10/2018 15:15, Andrew Rybchenko:
> On 10/11/18 3:59 PM, Thomas Monjalon wrote:
> > 11/10/2018 13:54, Andrew Rybchenko:
> >> On 10/11/18 2:45 PM, Thomas Monjalon wrote:
> >>> 11/10/2018 12:53, Andrew Rybchenko:
> >>>> On 10/8/18 1:09 AM, Thomas Monjalon wrote:
> >>>>> The PCI mapping requires to know the PCI driver to use,
> >>>>> even before the probing is done. That's why the PCI driver is
> >>>>> referenced early inside the PCI device structure. See
> >>>>> 1d20a073fa5e ("bus/pci: reference driver structure before mapping")
> >>>>>
> >>>>> However the rte_driver does not need to be referenced in rte_device
> >>>>> before the device probing is done.
> >>>>> By moving back this assignment at the end of the device probing,
> >>>>> it becomes possible to make clear the status of a rte_device.
> >>>>>
> >>>>> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> >>>>> ---
> >>>>> diff --git a/drivers/bus/pci/pci_common.c b/drivers/bus/pci/pci_common.c
> >>>>> index c7695d108..d63e68045 100644
> >>>>> --- a/drivers/bus/pci/pci_common.c
> >>>>> +++ b/drivers/bus/pci/pci_common.c
> >>>>> @@ -160,14 +160,12 @@ rte_pci_probe_one_driver(struct rte_pci_driver *dr,
> >>>>>     	 * driver flags for adjusting configuration.
> >>>>>     	 */
> >>>>>     	dev->driver = dr;
> >>>>> -	dev->device.driver = &dr->driver;
> >>>> It breaks net/sfc and I guess other drivers which use
> >>>> rte_eth_dma_zone_reserve()
> >>>> from probe. The function makes zone name using dev->device->driver->name.
> >>> Please, can you show code line where we does such access?
> >>>
> >>> I checked such access before and did not find some.
> >>> Anyway, it can be fixed by accessing rte_pci_driver->driver->name.
> >>> Note that rte_pci_driver is referenced in rte_pci_device.
> >> Below in snprintf(), in theory it can be called for vdev as well.
> >>
> >> const struct rte_memzone *
> >> rte_eth_dma_zone_reserve(const struct rte_eth_dev *dev, const char
> >> *ring_name,
> >>                            uint16_t queue_id, size_t size, unsigned align,
> >>                            int socket_id)
> >> {
> >>           char z_name[RTE_MEMZONE_NAMESIZE];
> >>           const struct rte_memzone *mz;
> >>
> >>           snprintf(z_name, sizeof(z_name), "%s_%s_%d_%d",
> >>                    dev->device->driver->name, ring_name,
> >>                    dev->data->port_id, queue_id);
> > I see, I missed it.
> >
> > I think it's strange to use rte_device name for ethdev memory.
> > Should we use the ethdev name instead?
> >
> >          snprintf(z_name, sizeof(z_name), "%s_%s_%d_%d",
> > -                dev->device->driver->name, ring_name,
> > +                dev->data->name, ring_name,
> >                   dev->data->port_id, queue_id);
> 
> data->name could be update to 63 characters (RTE_DEV_NAME_MAX_LEN=64).
> RTE_MEMZONE_NAMESIZE is 32. Sounds like a problem.
> It is especially a problem if name may be specified/set by user.
> 
> Right now device driver writer knows the driver name, choose ring name and
> have limits on port and queue ID. So, the writer at least has possibility to
> be sure that the results will always fit z_name.

What about removing the device name from the memzone name?
It is already unique thanks to port_id, queue_id and ring_name.