[PATCH] drm: Fix HDCP failures when SRM fw is missing

[Sean Paul]

From: Sean Paul <seanpaul at chromium.org>

The SRM cleanup in 79643fddd6eb2 ("drm/hdcp: optimizing the srm
handling") inadvertently altered the behavior of HDCP auth when
the SRM firmware is missing. Before that patch, missing SRM was
interpreted as the device having no revoked keys. With that patch,
if the SRM fw file is missing we reject _all_ keys.

This patch fixes that regression by returning success if the file
cannot be found.

Fixes: 79643fddd6eb ("drm/hdcp: optimizing the srm handling")
Cc: stable at vger.kernel.org
Cc: Ramalingam C <ramalingam.c at intel.com>
Cc: Sean Paul <sean at poorly.run>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: dri-devel at lists.freedesktop.org
Signed-off-by: Sean Paul <seanpaul at chromium.org>
---
 drivers/gpu/drm/drm_hdcp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_hdcp.c b/drivers/gpu/drm/drm_hdcp.c
index 7f386adcf872..3c36005d367b 100644
--- a/drivers/gpu/drm/drm_hdcp.c
+++ b/drivers/gpu/drm/drm_hdcp.c
@@ -241,8 +241,10 @@ static int drm_hdcp_request_srm(struct drm_device *drm_dev,
 
 	ret = request_firmware_direct(&fw, (const char *)fw_name,
 				      drm_dev->dev);
-	if (ret < 0)
+	if (ret < 0) {
+		ret = 0;
 		goto exit;
+	}
 
 	if (fw->size && fw->data)
 		ret = drm_hdcp_srm_update(fw->data, fw->size, revoked_ksv_list,
-- 
Sean Paul, Software Engineer, Google / Chromium OS