On Tue, Sep 23, 2014 at 04:46:06PM +0200, Antonios Motakis wrote: > As already demonstrated with PCI [1] and the platform bus [2], a > driver_override property in sysfs can be used to bypass the id matching > of a device to a AMBA driver. This can be used by VFIO to bind to any AMBA > device requested by the user. > > [1] http://lists-archives.com/linux-kernel/28030441-pci-introduce-new-device-binding-path-using-pci_dev-driver_override.html > [2] https://www.redhat.com/archives/libvir-list/2014-April/msg00382.html > > Signed-off-by: Antonios Motakis <a.motakis@xxxxxxxxxxxxxxxxxxxxxx> I have to ask why this is even needed in the first place. To take the example in [2], what's wrong with: echo fff51000.ethernet > /sys/bus/platform/devices/fff51000.ethernet/driver/unbind echo fff51000.ethernet > /sys/bus/platform/drivers/vfio-platform/bind and similar for AMBA. All we would need to do is to introduce a way of having a driver accept explicit bind requests. In any case: > +static ssize_t driver_override_store(struct device *_dev, > + struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + struct amba_device *dev = to_amba_device(_dev); > + char *driver_override, *old = dev->driver_override, *cp; > + > + if (count > PATH_MAX) > + return -EINVAL; > + > + driver_override = kstrndup(buf, count, GFP_KERNEL); > + if (!driver_override) > + return -ENOMEM; > + > + cp = strchr(driver_override, '\n'); > + if (cp) > + *cp = '\0'; I hope that is not replicated everywhere. This allows up to a page to be allocated, even when the first byte may be a newline. This is wasteful. How about: if (count > PATH_MAX) return -EINVAL; cp = strnchr(buf, count, '\n'); if (cp) count = cp - buf - 1; if (count) { driver_override = kstrndup(buf, count, GFP_KERNEL); if (!driver_override) return -ENOMEM; } else { driver_override = NULL; } kfree(dev->driver_override); dev->driver_override = driver_override; Also: > +static ssize_t driver_override_show(struct device *_dev, > + struct device_attribute *attr, char *buf) > +{ > + struct amba_device *dev = to_amba_device(_dev); > + > + return sprintf(buf, "%s\n", dev->driver_override); > +} Do we really want to do a NULL pointer dereference here? -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
