accessing a PCIe register from userspace through kmem or other ways ?

[Ryan Stone]

On Thu, Mar 31, 2016 at 4:39 PM, John Baldwin <jhb at freebsd.org> wrote:

> On Wednesday, March 30, 2016 11:20:51 AM Jim Harris wrote:
> > On Wed, Mar 30, 2016 at 10:47 AM, Luigi Rizzo <rizzo at iet.unipi.it>
> wrote:
> >
> > > Hi,
> > > I'd like to test the rate at which I can access device registers
> > > on a PCIe card, and was wondering whether I need to patch a device
> > > driver, or perhaps I can use /dev/kmem once I figure out where
> > > the registers are mapped ?
> > >
> >
> > You do not need to patch a device driver.  Have you looked at
> > libpciaccess?  This should give you everything you need.
>
> You can also look at what pciconf uses.  (It has a read_config() method
> that uses an ioctl on an fd of /dev/pci).
>

pciconf can only access the configuration space, right?  I believe that
Luigi is more interested in measuring the latency to a register mapped from
a BAR.