From d8b86cba3cd210976fd9dfc3551f185edfedbfb9 Mon Sep 17 00:00:00 2001
From: Peter Bigot <peter.bigot@nordicsemi.no>
Date: Mon, 22 Jun 2020 10:01:39 -0500
Subject: [PATCH] device: add API to check whether a device is ready to use

Currently this is useful only for some internal applications that
iterate over the device table, since applications can't get access to
a device that isn't ready, and devices can't be made unready.  So it's
introduced as internal API that may be exposed as device_ready() when
those conditions change.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
---
 include/device.h                      | 11 +++++++++++
 kernel/device.c                       |  6 ++----
 subsys/shell/modules/device_service.c |  4 ++--
 subsys/shell/shell_utils.c            |  2 +-
 4 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/include/device.h b/include/device.h
index 3ad62e7a26..98c05e5911 100644
--- a/include/device.h
+++ b/include/device.h
@@ -240,6 +240,17 @@ __syscall struct device *device_get_binding(const char *name);
  */
 size_t z_device_get_all_static(struct device **devices);
 
+/** @brief Determine whether a device has been successfully initialized.
+ *
+ * @param dev pointer to the device in question.
+ *
+ * @return true if and only if the device is available for use.
+ */
+static inline bool z_device_ready(const struct device *dev)
+{
+	return dev->driver_api != NULL;
+}
+
 /**
  * @}
  */
diff --git a/kernel/device.c b/kernel/device.c
index 24866cded7..b4fb179f85 100644
--- a/kernel/device.c
+++ b/kernel/device.c
@@ -86,15 +86,13 @@ struct device *z_impl_device_get_binding(const char *name)
 	 * performed. Reserve string comparisons for a fallback.
 	 */
 	for (dev = __device_start; dev != __device_end; dev++) {
-		if ((dev->driver_api != NULL) &&
-		    (dev->name == name)) {
+		if (z_device_ready(dev) && (dev->name == name)) {
 			return dev;
 		}
 	}
 
 	for (dev = __device_start; dev != __device_end; dev++) {
-		if ((dev->driver_api != NULL) &&
-		    (strcmp(name, dev->name) == 0)) {
+		if (z_device_ready(dev) && (strcmp(name, dev->name) == 0)) {
 			return dev;
 		}
 	}
diff --git a/subsys/shell/modules/device_service.c b/subsys/shell/modules/device_service.c
index 2ca89968da..1c1fb425f2 100644
--- a/subsys/shell/modules/device_service.c
+++ b/subsys/shell/modules/device_service.c
@@ -39,7 +39,7 @@ static bool device_get_config_level(const struct shell *shell, int level)
 	bool devices = false;
 
 	for (dev = levels[level]; dev < levels[level+1]; dev++) {
-		if (dev->driver_api != NULL) {
+		if (z_device_ready(dev)) {
 			devices = true;
 
 			shell_fprintf(shell, SHELL_NORMAL, "- %s\n", dev->name);
@@ -92,7 +92,7 @@ static int cmd_device_list(const struct shell *shell,
 	shell_fprintf(shell, SHELL_NORMAL, "devices:\n");
 
 	for (dev = __device_start; dev != __device_end; dev++) {
-		if (dev->driver_api == NULL) {
+		if (!z_device_ready(dev)) {
 			continue;
 		}
 
diff --git a/subsys/shell/shell_utils.c b/subsys/shell/shell_utils.c
index 245030cab4..87c6f27b4c 100644
--- a/subsys/shell/shell_utils.c
+++ b/subsys/shell/shell_utils.c
@@ -470,7 +470,7 @@ struct device *shell_device_lookup(size_t idx,
 	struct device *dev_end = dev + len;
 
 	while (dev < dev_end) {
-		if ((dev->driver_api != NULL)
+		if (z_device_ready(dev)
 		    && (dev->name != NULL)
 		    && (strlen(dev->name) != 0)
 		    && ((prefix == NULL)