driver: introduce less error-prone dev_get_drvdata alternative

We use dev_get_drvdata to get the driver match data associated with a
device. This has two shortcomings:

 - Linux has dev_get_drvdata too, which returns a private pointer for
   driver specific info to associate with a device. We use dev->priv
   (or more often container_of) for that in barebox instead

 - It nearly always involves a cast to a double pointer, which is
   error-prone as size and alignment match need to be ensured
   on the programmer's part and can easily be gotten wrong:
	enum dev_type type;
	dev_get_drvdata(dev, (const void **)&type); // UB!

Add a new function that instead of using a double pointer argument,
returns the pointer directly:

 - For normal pointer driver data, no cast is necessary
 - For integer driver data casted to a pointer for storage,
   the cast is still necessary, but it's only a single pointer
   this way

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/driver.h b/include/driver.h
index 154525e0fd..14220431f2 100644
--- a/include/driver.h
+++ b/include/driver.h
@@ -534,8 +534,26 @@ int devfs_create_partitions(const char *devname,
 #define DRV_OF_COMPAT(compat) \
 	IS_ENABLED(CONFIG_OFDEVICE) ? (compat) : NULL
 
+/**
+ * dev_get_drvdata - get driver match data associated with device
+ * @dev: device instance
+ * @data: pointer to void *, where match data is stored
+ *
+ * Returns 0 on success and error code otherwise.
+ *
+ * DEPRECATED: use device_get_match_data instead, which avoids
+ * common pitfalls due to explicit pointer casts
+ */
 int dev_get_drvdata(struct device_d *dev, const void **data);
 
+/**
+ * device_get_match_data - get driver match data associated with device
+ * @dev: device instance
+ *
+ * Returns match data on success and NULL otherwise
+ */
+const void *device_get_match_data(struct device_d *dev);
+
 int device_match_of_modalias(struct device_d *dev, struct driver_d *drv);
 
 #endif /* DRIVER_H */