driver core: prevent deferred probe with platform_driver_probe

Prevent drivers relying on platform_driver_probe from requesting
deferred probing in order to avoid further futile probe attempts (either
the driver has been unregistered or its probe function has been set to
platform_drv_probe_fail when probing is retried).

Note that several platform drivers currently return subsystem errors
from probe and that these can include -EPROBE_DEFER (e.g. if a gpio
request fails).

Add a warning to platform_drv_probe that can be used to catch drivers
that inadvertently request probe deferral while using
platform_driver_probe.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 4f8bef3..47051cd 100644 (file)
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -488,6 +488,11 @@ static int platform_drv_probe(struct device *_dev)
        if (ret && ACPI_HANDLE(_dev))
                acpi_dev_pm_detach(_dev, true);
 
+       if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) {
+               dev_warn(_dev, "probe deferral not supported\n");
+               ret = -ENXIO;
+       }
+
        return ret;
 }
 
@@ -553,8 +558,7 @@ EXPORT_SYMBOL_GPL(platform_driver_unregister);
 /**
  * platform_driver_probe - register driver for non-hotpluggable device
  * @drv: platform driver structure
- * @probe: the driver probe routine, probably from an __init section,
- *         must not return -EPROBE_DEFER.
+ * @probe: the driver probe routine, probably from an __init section
  *
  * Use this instead of platform_driver_register() when you know the device
  * is not hotpluggable and has already been registered, and you want to
@@ -565,8 +569,7 @@ EXPORT_SYMBOL_GPL(platform_driver_unregister);
  * into system-on-chip processors, where the controller devices have been
  * configured as part of board setup.
  *
- * This is incompatible with deferred probing so probe() must not
- * return -EPROBE_DEFER.
+ * Note that this is incompatible with deferred probing.
  *
  * Returns zero if the driver registered and bound to a device, else returns
  * a negative error code and with the driver not registered.
@@ -576,6 +579,12 @@ int __init_or_module platform_driver_probe(struct platform_driver *drv,
 {
        int retval, code;
 
+       /*
+        * Prevent driver from requesting probe deferral to avoid further
+        * futile probe attempts.
+        */
+       drv->prevent_deferred_probe = true;
+
        /* make sure driver won't have bind/unbind attributes */
        drv->driver.suppress_bind_attrs = true;
 

diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index ce8e4ff..16f6654 100644 (file)
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -178,6 +178,7 @@ struct platform_driver {
        int (*resume)(struct platform_device *);
        struct device_driver driver;
        const struct platform_device_id *id_table;
+       bool prevent_deferred_probe;
 };
 
 #define to_platform_driver(drv)        (container_of((drv), struct platform_driver, \