> Dan Williams wrote:
> > Kobayashi,Daisuke wrote:
> > > Add sysfs attribute for CXL 1.1 device link status to the cxl pci device.
> > >
> > > In CXL1.1, the link status of the device is included in the RCRB mapped to
> > > the memory mapped register area. Critically, that arrangement makes the
> link
> > > status and control registers invisible to existing PCI user tooling.
> > >
> > > Export those registers via sysfs with the expectation that PCI user
> > > tooling will alternatively look for these sysfs files when attempting to
> > > access to these CXL 1.1 endpoints registers.
> > >
> > > Signed-off-by: "Kobayashi,Daisuke" <kobayashi.da-06@xxxxxxxxxxx>
> > > ---
> > > drivers/cxl/pci.c | 74
> +++++++++++++++++++++++++++++++++++++++++++++++
> > > 1 file changed, 74 insertions(+)
> > >
> > > diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> > > index 2ff361e756d6..0ff15738b1ba 100644
> > > --- a/drivers/cxl/pci.c
> > > +++ b/drivers/cxl/pci.c
> [..]
> > 3/ The port corresponding to a memdev can disappear at any time so you
> > need to do the same validation the cxl_mem_probe() does to keep the port
> > active during the register access:
> >
> > guard(device)(&port->dev);
> > if (!port->dev.driver)
> > return -ENXIO;
>
> Apologies, I made a mistake here. Copy how cxl_mem_probe() accesses the
> dport.
>
> endpoint_parent = port->uport_dev;
> guard(device)(&endpoint_parent->dev);
> if (!endpoint_parent->driver)
> return -ENXIO;
Thank you for your feedback.
I could not find the exact same code as the suggestion from cxl_mem_probe(),
but would your suggestion be correct with the following modification:
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index 2ff361e756d6..0ff15738b1ba 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -786,6 +786,79 @@ static int cxl_event_config(struct pci_host_bridge *host_bridge,
return 0;
}
+static ssize_t rcd_link_cap_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct cxl_port *port;
+ struct cxl_dport *dport;
+ struct cxl_dev_state *cxlds = dev_get_drvdata(dev);
+ struct cxl_memdev *cxlmd = cxlds->cxlmd;
+ struct device *endpoint_parent;
+
+ port = cxl_mem_find_port(cxlmd, &dport);
+ if (!port)
+ return -EINVAL;
+
+ endpoint_parent = port->uport_dev;
+ guard(device)(&endpoint_parent);
+ if (!endpoint_parent->driver)
+ return -ENXIO;
+ return sysfs_emit(buf, "%x\n", dport->rcrb.rcd_lnkcap);
+}
+static DEVICE_ATTR_RO(rcd_link_cap);
[..]
--
>From reading the guard macro, my understanding is that this is a macro which
calls the constructor here, and calls the destructor when the scope is exited.
Will this prevent the port from disappearing?
