driver core: add test of driver remove calls during probe

In recent discussions on ksummit-discuss[1], it was suggested to do a
sequence of probe, remove, probe for testing driver remove paths. This
adds a kconfig option for said test.

[1] https://lists.linuxfoundation.org/pipermail/ksummit-discuss/2016-August/003459.html

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 31 insertions, 0 deletions

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 98504ec99c7d..fdf44cac08e6 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -212,6 +212,16 @@ config DEBUG_DEVRES
 
           If you are unsure about this, Say N here.
 
+config DEBUG_TEST_DRIVER_REMOVE
+        bool "Test driver remove calls during probe"
+        depends on DEBUG_KERNEL
+        help
+          Say Y here if you want the Driver core to test driver remove functions
+          by calling probe, remove, probe. This tests the remove path without
+          having to unbind the driver or unload the driver module.
+
+          If you are unsure about this, say N here.
+
 config SYS_HYPERVISOR
         bool
         default n
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 16688f50729c..4910e6db2a34 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -329,6 +329,7 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 {
         int ret = -EPROBE_DEFER;
         int local_trigger_count = atomic_read(&deferred_trigger_count);
+        bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE);
 
         if (defer_all_probes) {
                 /*
@@ -346,6 +347,7 @@ static int really_probe(struct device *dev, struct device_driver *drv)
                  drv->bus->name, __func__, drv->name, dev_name(dev));
         WARN_ON(!list_empty(&dev->devres_head));
 
+re_probe:
         dev->driver = drv;
 
         /* If using pinctrl, bind pins now before probing */
@@ -383,6 +385,25 @@ static int really_probe(struct device *dev, struct device_driver *drv)
                         goto probe_failed;
         }
 
+        if (test_remove) {
+                test_remove = false;
+
+                if (dev->bus && dev->bus->remove)
+                        dev->bus->remove(dev);
+                else if (drv->remove)
+                        drv->remove(dev);
+
+                devres_release_all(dev);
+                driver_sysfs_remove(dev);
+                dev->driver = NULL;
+                dev_set_drvdata(dev, NULL);
+                if (dev->pm_domain && dev->pm_domain->dismiss)
+                        dev->pm_domain->dismiss(dev);
+                pm_runtime_reinit(dev);
+
+                goto re_probe;
+        }
+
         pinctrl_init_done(dev);
 
         if (dev->pm_domain && dev->pm_domain->sync)