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, 11 insertions, 0 deletions

diff --git a/drivers/base/driver.c b/drivers/base/driver.c
index 412db6c406..3205bbc3c3 100644
--- a/drivers/base/driver.c
+++ b/drivers/base/driver.c
@@ -500,3 +500,14 @@ int dev_get_drvdata(struct device_d *dev, const void **data)
 
 	return -ENODEV;
 }
+
+const void *device_get_match_data(struct device_d *dev)
+{
+	if (dev->of_id_entry)
+		return dev->of_id_entry->data;
+
+	if (dev->id_entry)
+		return (void *)dev->id_entry->driver_data;
+
+	return NULL;
+}