[PATCH] PCI: endpoint: Fix NULL pointer dereference error when CONFIGFS is disabled

[Kishon Vijay Abraham I]

commit ef1433f717a2c63747a519d86965d73 ("PCI: endpoint: Create configfs
entry for each pci_epf_device_id table entry") while adding configfs
entry for each pci_epf_device_id table entry introduced a NULL pointer
dereference error when CONFIG_PCI_ENDPOINT_CONFIGFS is not enabled.
Fix it here.

Fixes: ef1433f717a2c63747a519d86965d73 ("PCI: endpoint: Create configfs
entry for each pci_epf_device_id table entry")

Signed-off-by: Kishon Vijay Abraham I <kis...@ti.com>
---
 drivers/pci/endpoint/pci-epf-core.c | 62 ++++++++++++++++++++---------
 1 file changed, 43 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/endpoint/pci-epf-core.c 
b/drivers/pci/endpoint/pci-epf-core.c
index 523a8cab3bfb..7fe1930d6589 100644
--- a/drivers/pci/endpoint/pci-epf-core.c
+++ b/drivers/pci/endpoint/pci-epf-core.c
@@ -137,25 +137,60 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t 
size, enum pci_barno bar)
 }
 EXPORT_SYMBOL_GPL(pci_epf_alloc_space);
 
-/**
- * pci_epf_unregister_driver() - unregister the PCI EPF driver
- * @driver: the PCI EPF driver that has to be unregistered
- *
- * Invoke to unregister the PCI EPF driver.
- */
-void pci_epf_unregister_driver(struct pci_epf_driver *driver)
+static void pci_epf_remove_cfs(struct pci_epf_driver *driver)
 {
        struct config_group *group;
 
+       if (!IS_ENABLED(CONFIG_PCI_ENDPOINT_CONFIGFS))
+               return;
+
        mutex_lock(&pci_epf_mutex);
        list_for_each_entry(group, &driver->epf_group, group_entry)
                pci_ep_cfs_remove_epf_group(group);
        list_del(&driver->epf_group);
        mutex_unlock(&pci_epf_mutex);
+}
+
+/**
+ * pci_epf_unregister_driver() - unregister the PCI EPF driver
+ * @driver: the PCI EPF driver that has to be unregistered
+ *
+ * Invoke to unregister the PCI EPF driver.
+ */
+void pci_epf_unregister_driver(struct pci_epf_driver *driver)
+{
+       pci_epf_remove_cfs(driver);
        driver_unregister(&driver->driver);
 }
 EXPORT_SYMBOL_GPL(pci_epf_unregister_driver);
 
+static int pci_epf_add_cfs(struct pci_epf_driver *driver)
+{
+       struct config_group *group;
+       const struct pci_epf_device_id *id;
+
+       if (!IS_ENABLED(CONFIG_PCI_ENDPOINT_CONFIGFS))
+               return 0;
+
+       INIT_LIST_HEAD(&driver->epf_group);
+
+       id = driver->id_table;
+       while (id->name[0]) {
+               group = pci_ep_cfs_add_epf_group(id->name);
+               if (IS_ERR(group)) {
+                       pci_epf_remove_cfs(driver);
+                       return PTR_ERR(group);
+               }
+
+               mutex_lock(&pci_epf_mutex);
+               list_add_tail(&group->group_entry, &driver->epf_group);
+               mutex_unlock(&pci_epf_mutex);
+               id++;
+       }
+
+       return 0;
+}
+
 /**
  * __pci_epf_register_driver() - register a new PCI EPF driver
  * @driver: structure representing PCI EPF driver
@@ -167,8 +202,6 @@ int __pci_epf_register_driver(struct pci_epf_driver *driver,
                              struct module *owner)
 {
        int ret;
-       struct config_group *group;
-       const struct pci_epf_device_id *id;
 
        if (!driver->ops)
                return -EINVAL;
@@ -183,16 +216,7 @@ int __pci_epf_register_driver(struct pci_epf_driver 
*driver,
        if (ret)
                return ret;
 
-       INIT_LIST_HEAD(&driver->epf_group);
-
-       id = driver->id_table;
-       while (id->name[0]) {
-               group = pci_ep_cfs_add_epf_group(id->name);
-               mutex_lock(&pci_epf_mutex);
-               list_add_tail(&group->group_entry, &driver->epf_group);
-               mutex_unlock(&pci_epf_mutex);
-               id++;
-       }
+       pci_epf_add_cfs(driver);
 
        return 0;
 }
-- 
2.17.1