PCI: add remove_id sysfs entry

This adds a remove_id sysfs entry to allow users of new_id to later
remove the added dynid.  One use case is management tools that want to
dynamically bind/unbind devices to pci-stub driver while devices are
assigned to KVM guests.  Rather than having to track which driver was
originally bound to the driver, a mangement tool can simply:

Guest uses device

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

2 files changed, 94 insertions, 2 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index e638e15a8895..3d29793a0ea2 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -41,6 +41,22 @@ Description:
                 for the device and attempt to bind to it.  For example:
                 # echo "8086 10f5" > /sys/bus/pci/drivers/foo/new_id
 
+What:           /sys/bus/pci/drivers/.../remove_id
+Date:           February 2009
+Contact:        Chris Wright <chrisw@sous-sol.org>
+Description:
+                Writing a device ID to this file will remove an ID
+                that was dynamically added via the new_id sysfs entry.
+                The format for the device ID is:
+                VVVV DDDD SVVV SDDD CCCC MMMM.  That is Vendor ID, Device
+                ID, Subsystem Vendor ID, Subsystem Device ID, Class,
+                and Class Mask.  The Vendor ID and Device ID fields are
+                required, the rest are optional.  After successfully
+                removing an ID, the driver will no longer support the
+                device.  This is useful to ensure auto probing won't
+                match the driver to the device.  For example:
+                # echo "8086 10f5" > /sys/bus/pci/drivers/foo/remove_id
+
 What:           /sys/bus/pci/devices/.../vpd
 Date:           February 2008
 Contact:        Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 93eac1423585..87a5ddbb324f 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -99,6 +99,52 @@ store_new_id(struct device_driver *driver, const char *buf, size_t count)
 }
 static DRIVER_ATTR(new_id, S_IWUSR, NULL, store_new_id);
 
+/**
+ * store_remove_id - remove a PCI device ID from this driver
+ * @driver: target device driver
+ * @buf: buffer for scanning device ID data
+ * @count: input size
+ *
+ * Removes a dynamic pci device ID to this driver.
+ */
+static ssize_t
+store_remove_id(struct device_driver *driver, const char *buf, size_t count)
+{
+        struct pci_dynid *dynid, *n;
+        struct pci_driver *pdrv = to_pci_driver(driver);
+        __u32 vendor, device, subvendor = PCI_ANY_ID,
+                subdevice = PCI_ANY_ID, class = 0, class_mask = 0;
+        int fields = 0;
+        int retval = -ENODEV;
+
+        fields = sscanf(buf, "%x %x %x %x %x %x",
+                        &vendor, &device, &subvendor, &subdevice,
+                        &class, &class_mask);
+        if (fields < 2)
+                return -EINVAL;
+
+        spin_lock(&pdrv->dynids.lock);
+        list_for_each_entry_safe(dynid, n, &pdrv->dynids.list, node) {
+                struct pci_device_id *id = &dynid->id;
+                if ((id->vendor == vendor) &&
+                    (id->device == device) &&
+                    (subvendor == PCI_ANY_ID || id->subvendor == subvendor) &&
+                    (subdevice == PCI_ANY_ID || id->subdevice == subdevice) &&
+                    !((id->class ^ class) & class_mask)) {
+                        list_del(&dynid->node);
+                        kfree(dynid);
+                        retval = 0;
+                        break;
+                }
+        }
+        spin_unlock(&pdrv->dynids.lock);
+
+        if (retval)
+                return retval;
+        return count;
+}
+static DRIVER_ATTR(remove_id, S_IWUSR, NULL, store_remove_id);
+
 static void
 pci_free_dynids(struct pci_driver *drv)
 {
@@ -125,6 +171,20 @@ static void pci_remove_newid_file(struct pci_driver *drv)
 {
         driver_remove_file(&drv->driver, &driver_attr_new_id);
 }
+
+static int
+pci_create_removeid_file(struct pci_driver *drv)
+{
+        int error = 0;
+        if (drv->probe != NULL)
+                error = driver_create_file(&drv->driver,&driver_attr_remove_id);
+        return error;
+}
+
+static void pci_remove_removeid_file(struct pci_driver *drv)
+{
+        driver_remove_file(&drv->driver, &driver_attr_remove_id);
+}
 #else /* !CONFIG_HOTPLUG */
 static inline void pci_free_dynids(struct pci_driver *drv) {}
 static inline int pci_create_newid_file(struct pci_driver *drv)
@@ -132,6 +192,11 @@ static inline int pci_create_newid_file(struct pci_driver *drv)
         return 0;
 }
 static inline void pci_remove_newid_file(struct pci_driver *drv) {}
+static inline int pci_create_removeid_file(struct pci_driver *drv)
+{
+        return 0;
+}
+static inline void pci_remove_removeid_file(struct pci_driver *drv) {}
 #endif
 
 /**
@@ -852,13 +917,23 @@ int __pci_register_driver(struct pci_driver *drv, struct module *owner,
         /* register with core */
         error = driver_register(&drv->driver);
         if (error)
-                return error;
+                goto out;
 
         error = pci_create_newid_file(drv);
         if (error)
-                driver_unregister(&drv->driver);
+                goto out_newid;
 
+        error = pci_create_removeid_file(drv);
+        if (error)
+                goto out_removeid;
+out:
         return error;
+
+out_removeid:
+        pci_remove_newid_file(drv);
+out_newid:
+        driver_unregister(&drv->driver);
+        goto out;
 }
 
 /**
@@ -874,6 +949,7 @@ int __pci_register_driver(struct pci_driver *drv, struct module *owner,
 void
 pci_unregister_driver(struct pci_driver *drv)
 {
+        pci_remove_removeid_file(drv);
         pci_remove_newid_file(drv);
         driver_unregister(&drv->driver);
         pci_free_dynids(drv);