Re: [PATCH V3 1/6] vDPA/ifcvf: get_vendor_id returns a device specific vendor id

[Zhu Lingshan]

On 3/11/2021 11:23 AM, Jason Wang wrote:
> On 2021/3/10 5:00 下午, Zhu Lingshan wrote:
> > In this commit, ifcvf_get_vendor_id() will return
> > a device specific vendor id of the probed pci device
> > than a hard code.
> >
> > Signed-off-by: Zhu Lingshan <lingshan.zhu@xxxxxxxxx>
> > ---
> >   drivers/vdpa/ifcvf/ifcvf_main.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
> > b/drivers/vdpa/ifcvf/ifcvf_main.c
> > index fa1af301cf55..e501ee07de17 100644
> > --- a/drivers/vdpa/ifcvf/ifcvf_main.c
> > +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> > @@ -324,7 +324,10 @@ static u32 ifcvf_vdpa_get_device_id(struct 
> > vdpa_device *vdpa_dev)
> >     static u32 ifcvf_vdpa_get_vendor_id(struct vdpa_device *vdpa_dev)
> >   {
> > -    return IFCVF_SUBSYS_VENDOR_ID;
> > +    struct ifcvf_adapter *adapter = vdpa_to_adapter(vdpa_dev);
> > +    struct pci_dev *pdev = adapter->pdev;
> > +
> > +    return pdev->subsystem_vendor;
> >   }
>
>
> While at this, I wonder if we can do something similar in 
> get_device_id() if it could be simple deduced from some simple math 
> from the pci device id?
>
> Thanks
Hi Jason,

IMHO, this implementation is just some memory read ops, I think other 
implementations may not save many cpu cycles, an if cost at least three 
cpu cycles.

Thanks!
> >     static u32 ifcvf_vdpa_get_vq_align(struct vdpa_device *vdpa_dev)