firmware: enable to force disable the fallback mechanism at run time

You currently need four different kernel builds to test the firmware
API fully. By adding a proc knob to force disable the fallback mechanism
completely we are able to reduce the amount of kernels you need built
to test the firmware API down to two.

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
index 45cc40933a47..d6838e7ec00c 100644
--- a/drivers/base/firmware_loader/fallback.c
+++ b/drivers/base/firmware_loader/fallback.c
@@ -643,6 +643,11 @@ static bool fw_force_sysfs_fallback(unsigned int opt_flags)
 
 static bool fw_run_sysfs_fallback(unsigned int opt_flags)
 {
+        if (fw_fallback_config.ignore_sysfs_fallback) {
+                pr_info_once("Ignoring firmware sysfs fallback due to debugfs knob\n");
+                return false;
+        }
+
         if ((opt_flags & FW_OPT_NOFALLBACK))
                 return false;