[PATCH v2 20/23] firmware: add debug facility to emulate disabling sysfs fallback

["Luis R. Rodriguez" <mcgrof@kernel.org>]

One can build a kernel without CONFIG_FW_LOADER_USER_HELPER being
enabled, but testing it requires a unique kernel configuration most
folks do not enable. This makes it hard to test.

Provide a debugfs facility to enable us to emulate such kernels.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
 drivers/base/firmware_debug.c  |  5 +++++
 drivers/base/firmware_debug.h  | 14 ++++++++++++++
 drivers/base/firmware_loader.c |  5 +++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/base/firmware_debug.c b/drivers/base/firmware_debug.c
index f2817eb6f480..9332f0acfa8f 100644
--- a/drivers/base/firmware_debug.c
+++ b/drivers/base/firmware_debug.c
@@ -20,6 +20,11 @@ int __init register_fw_debugfs(void)
 				 &fw_debug.force_sysfs_fallback))
 		goto err_out;
 
+	if (!debugfs_create_bool("ignore_sysfs_fallback", S_IRUSR | S_IWUSR,
+				 debugfs_firmware,
+				 &fw_debug.ignore_sysfs_fallback))
+		goto err_out;
+
 	return 0;
 err_out:
 	debugfs_remove_recursive(debugfs_firmware);
diff --git a/drivers/base/firmware_debug.h b/drivers/base/firmware_debug.h
index bc41bbca9a54..5f551d8b9003 100644
--- a/drivers/base/firmware_debug.h
+++ b/drivers/base/firmware_debug.h
@@ -12,9 +12,13 @@
  *	as if one had enabled CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y.
  *	Useful to help debug a CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
  *	functionality on a kernel where that config entry has been disabled.
+ * @ignore_sysfs_fallback: force to disable the sysfs fallback mechanism.
+ * 	This emulates the behaviour as if we had set the kernel
+ * 	config CONFIG_FW_LOADER_USER_HELPER=n.
  */
 struct firmware_debug {
 	bool force_sysfs_fallback;
+	bool ignore_sysfs_fallback;
 };
 
 extern struct firmware_debug fw_debug;
@@ -26,6 +30,11 @@ static inline bool fw_debug_force_sysfs_fallback(void)
 {
 	return fw_debug.force_sysfs_fallback;
 }
+
+static inline bool fw_debug_ignore_sysfs_fallback(void)
+{
+	return fw_debug.ignore_sysfs_fallback;
+}
 #else
 static inline int register_fw_debugfs(void)
 {
@@ -39,6 +48,11 @@ static inline bool fw_debug_force_sysfs_fallback(void)
 {
 	return false;
 }
+
+static inline bool fw_debug_ignore_sysfs_fallback(void)
+{
+	return false;
+}
 #endif /* CONFIG_FW_LOADER_DEBUG */
 
 #endif /* __FIRMWARE_DEBUG_H */
diff --git a/drivers/base/firmware_loader.c b/drivers/base/firmware_loader.c
index b2b52ba9f245..6c44ede98be0 100644
--- a/drivers/base/firmware_loader.c
+++ b/drivers/base/firmware_loader.c
@@ -1170,6 +1170,11 @@ static bool fw_force_sysfs_fallback(unsigned int opt_flags)
 
 static bool fw_run_sysfs_fallback(unsigned int opt_flags)
 {
+	if (fw_debug_ignore_sysfs_fallback()) {
+		pr_info("Ignoring firmware sysfs fallback due to debugfs knob\n");
+		return false;
+	}
+
 	if ((opt_flags & FW_OPT_NOFALLBACK))
 		return false;
 
-- 
2.15.0