driver core: have match() callback in struct bus_type take a const *

In the match() callback, the struct device_driver * should not be
changed, so change the function callback to be a const *.  This is one
step of many towards making the driver core safe to have struct
device_driver in read-only memory.

Because the match() callback is in all busses, all busses are modified
to handle this properly.  This does entail switching some container_of()
calls to container_of_const() to properly handle the constant *.

For some busses, like PCI and USB and HV, the const * is cast away in
the match callback as those busses do want to modify those structures at
this point in time (they have a local lock in the driver structure.)
That will have to be changed in the future if they wish to have their
struct device * in read-only-memory.

Cc: Rafael J. Wysocki <rafael@kernel.org>
Reviewed-by: Alex Elder <elder@kernel.org>
Acked-by: Sumit Garg <sumit.garg@linaro.org>
Link: https://lore.kernel.org/r/2024070136-wrongdoer-busily-01e8@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 10 deletions

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 3ef9550bd2ca..fde29e0ad68b 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -39,12 +39,9 @@ static int dax_bus_uevent(const struct device *dev, struct kobj_uevent_env *env)
 	return add_uevent_var(env, "MODALIAS=" DAX_DEVICE_MODALIAS_FMT, 0);
 }
 
-static struct dax_device_driver *to_dax_drv(struct device_driver *drv)
-{
-	return container_of(drv, struct dax_device_driver, drv);
-}
+#define to_dax_drv(__drv)	container_of_const(__drv, struct dax_device_driver, drv)
 
-static struct dax_id *__dax_match_id(struct dax_device_driver *dax_drv,
+static struct dax_id *__dax_match_id(const struct dax_device_driver *dax_drv,
 		const char *dev_name)
 {
 	struct dax_id *dax_id;
@@ -57,7 +54,7 @@ static struct dax_id *__dax_match_id(struct dax_device_driver *dax_drv,
 	return NULL;
 }
 
-static int dax_match_id(struct dax_device_driver *dax_drv, struct device *dev)
+static int dax_match_id(const struct dax_device_driver *dax_drv, struct device *dev)
 {
 	int match;
 
@@ -68,7 +65,7 @@ static int dax_match_id(struct dax_device_driver *dax_drv, struct device *dev)
 	return match;
 }
 
-static int dax_match_type(struct dax_device_driver *dax_drv, struct device *dev)
+static int dax_match_type(const struct dax_device_driver *dax_drv, struct device *dev)
 {
 	enum dax_driver_type type = DAXDRV_DEVICE_TYPE;
 	struct dev_dax *dev_dax = to_dev_dax(dev);
@@ -156,7 +153,7 @@ static struct attribute *dax_drv_attrs[] = {
 };
 ATTRIBUTE_GROUPS(dax_drv);
 
-static int dax_bus_match(struct device *dev, struct device_driver *drv);
+static int dax_bus_match(struct device *dev, const struct device_driver *drv);
 
 /*
  * Static dax regions are regions created by an external subsystem
@@ -250,9 +247,9 @@ static const struct bus_type dax_bus_type = {
 	.drv_groups = dax_drv_groups,
 };
 
-static int dax_bus_match(struct device *dev, struct device_driver *drv)
+static int dax_bus_match(struct device *dev, const struct device_driver *drv)
 {
-	struct dax_device_driver *dax_drv = to_dax_drv(drv);
+	const struct dax_device_driver *dax_drv = to_dax_drv(drv);
 
 	if (dax_match_id(dax_drv, dev))
 		return 1;