device: fix potential truncation of DT-derived device names

While using the encoded path to a device tree node guarantees a unique
identifier for the corresponding device there is a limit on the number
of characters of that name that can be captured when looking up a
device by name from user mode, and the path can exceed that limit.

Synthesize a unique name from the node dependency ordinal instead, and
update the gen_defines script to record the name associated with the
full path in the extern declaration.

Add a build-time check that no device is created with a name that
violates the user mode requirement.

Also update the network device DTS helper functions to use the same
inference for dev_name and label that the real one does, since they
bypass the real one.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>

include/device.h

@@ -99,7 +99,8 @@ extern "C" {
  * since the API is not specified;
  *
  * @param dev_name Device name. This must be less than Z_DEVICE_MAX_NAME_LEN
- * characters in order to be looked up from user mode with device_get_binding().
+ * characters (including terminating NUL) in order to be looked up from user
+ * mode with device_get_binding().
  *
  * @param drv_name The name this instance of the driver exposes to
  * the system.
@@ -168,7 +169,7 @@ extern "C" {
  */
 #define DEVICE_DT_DEFINE(node_id, init_fn, pm_control_fn,		\
 			 data_ptr, cfg_ptr, level, prio, api_ptr)	\
-	Z_DEVICE_DEFINE(node_id, node_id,				\
+	Z_DEVICE_DEFINE(node_id, Z_DEVICE_DT_DEV_NAME(node_id),		\
 			DT_PROP_OR(node_id, label, NULL), init_fn,	\
 			pm_control_fn,					\
 			data_ptr, cfg_ptr, level, prio, api_ptr)
@@ -202,7 +203,7 @@ extern "C" {
  * @return The expanded name of the device object created by
  * DEVICE_DT_DEFINE()
  */
-#define DEVICE_DT_NAME_GET(node_id) DEVICE_NAME_GET(node_id)
+#define DEVICE_DT_NAME_GET(node_id) DEVICE_NAME_GET(Z_DEVICE_DT_DEV_NAME(node_id))
 
 /**
  * @def DEVICE_DT_GET
@@ -688,10 +689,20 @@ static inline int device_pm_put_sync(const struct device *dev) { return -ENOTSUP
  * @}
  */
 
+/* Node paths can exceed the maximum size supported by device_get_binding() in user mode,
+ * so synthesize a unique dev_name from the devicetree node.
+ *
+ * The ordinal used in this name can be mapped to the path by
+ * examining zephyr/include/generated/device_extern.h header.  If the
+ * format of this conversion changes, gen_defines should be updated to
+ * match it.
+ */
+#define Z_DEVICE_DT_DEV_NAME(node_id) _CONCAT(dts_ord_, DT_DEP_ORD(node_id))
+
 #define Z_DEVICE_DEFINE(node_id, dev_name, drv_name, init_fn, pm_control_fn, \
 			data_ptr, cfg_ptr, level, prio, api_ptr)	\
 	Z_DEVICE_DEFINE_PM(dev_name)					\
-	COND_CODE_1(DT_NODE_EXISTS(dev_name), (), (static))		\
+	COND_CODE_1(DT_NODE_EXISTS(node_id), (), (static))		\
 		const Z_DECL_ALIGN(struct device)			\
 		DEVICE_NAME_GET(dev_name) __used			\
 	__attribute__((__section__(".device_" #level STRINGIFY(prio)))) = { \
@@ -701,8 +712,10 @@ static inline int device_pm_put_sync(const struct device *dev) { return -ENOTSUP
 		.data = (data_ptr),					\
 		Z_DEVICE_DEFINE_PM_INIT(dev_name, pm_control_fn)	\
 	};								\
-	Z_INIT_ENTRY_DEFINE(_CONCAT(__device_, dev_name), init_fn,	\
-			    (&_CONCAT(__device_, dev_name)), level, prio)
+	BUILD_ASSERT(sizeof(Z_STRINGIFY(drv_name)) <= Z_DEVICE_MAX_NAME_LEN, \
+		     Z_STRINGIFY(DEVICE_GET_NAME(drv_name)) " too long"); \
+	Z_INIT_ENTRY_DEFINE(DEVICE_NAME_GET(dev_name), init_fn,		\
+		(&DEVICE_NAME_GET(dev_name)), level, prio)
 
 #ifdef CONFIG_PM_DEVICE
 #define Z_DEVICE_DEFINE_PM(dev_name)					\

include/net/ethernet.h

@@ -711,7 +711,8 @@ static inline bool net_eth_get_vlan_status(struct net_if *iface)
  */
 #define ETH_NET_DEVICE_DT_DEFINE(node_id, init_fn, pm_control_fn, data,	\
 			       cfg, prio, api, mtu)			\
-	Z_ETH_NET_DEVICE_INIT(node_id, node_id, DT_LABEL(node_id),	\
+	Z_ETH_NET_DEVICE_INIT(node_id, Z_DEVICE_DT_DEV_NAME(node_id),	\
+			      DT_PROP_OR(node_id, label, NULL),		\
 			      init_fn, pm_control_fn, data, cfg, prio,	\
 			      api, mtu)
 

include/net/net_if.h

@@ -2268,7 +2268,8 @@ struct net_if_api {
  */
 #define NET_DEVICE_DT_DEFINE(node_id, init_fn, pm_control_fn, data, cfg,	\
 			   prio, api, l2, l2_ctx_type, mtu)		\
-	Z_NET_DEVICE_INIT(node_id, node_id, DT_LABEL(node_id), init_fn,	\
+	Z_NET_DEVICE_INIT(node_id, Z_DEVICE_DT_DEV_NAME(node_id),	\
+			  DT_PROP_OR(node_id, label, NULL), init_fn,	\
 			  pm_control_fn, data, cfg, prio, api, l2,	\
 			  l2_ctx_type, mtu)
 

scripts/dts/gen_defines.py

@@ -132,7 +132,8 @@ def write_device_extern_header(device_header_out, edt):
         print("", file=dev_header_file)
 
         for node in sorted(edt.nodes, key=lambda node: node.dep_ordinal):
-            print(f"extern const struct device DEVICE_DT_NAME_GET(DT_{node.z_path_id});", file=dev_header_file)
+            print(f"extern const struct device DEVICE_DT_NAME_GET(DT_{node.z_path_id}); /* dts_ord_{node.dep_ordinal} */",
+                  file=dev_header_file)
 
         print("", file=dev_header_file)
         print("#ifdef __cplusplus", file=dev_header_file)