[PATCH] drm/fbdev-client: Ignore EOPNOTSUPP errors

[Thierry Reding <thierry.reding@gmail.com>]

From: Thierry Reding <treding@nvidia.com>

Recent generations of Tegra have moved the display components outside of
host1x, leading to a device that has no CRTCs attached and hence doesn't
support any of the modesetting functionality. When this is detected, the
driver clears the DRIVER_MODESET and DRIVER_ATOMIC flags for the device.

Unfortunately, this causes the following errors during boot:

    [      15.418958] ERR KERN drm drm: [drm] *ERROR* Failed to register client: -95
    [      15.425311] WARNING KERN drm drm: [drm] Failed to set up DRM client; error -95

These originate from the fbdev client checking for the presence of the
DRIVER_MODESET flag and returning -EOPNOTSUPP. However, if a driver does
not support DRIVER_MODESET this is entirely expected and the error isn't
helpful.

One solution would have been to conditionally call drm_client_setup()
only if modesetting is supported. This seems a bit redundant, however,
and could further complicate things if ever any DRM clients are added
that do not rely on modesetting.

Instead, simply add an extra check to ignore this expected error and
skip the fbdev client registration.

Reported-by: Jonathan Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 drivers/gpu/drm/clients/drm_fbdev_client.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/clients/drm_fbdev_client.c b/drivers/gpu/drm/clients/drm_fbdev_client.c
index f894ba52bdb5..8c8552ed912e 100644
--- a/drivers/gpu/drm/clients/drm_fbdev_client.c
+++ b/drivers/gpu/drm/clients/drm_fbdev_client.c
@@ -152,7 +152,11 @@ int drm_fbdev_client_setup(struct drm_device *dev, const struct drm_format_info
 
 	ret = drm_client_init(dev, &fb_helper->client, "fbdev", &drm_fbdev_client_funcs);
 	if (ret) {
-		drm_err(dev, "Failed to register client: %d\n", ret);
+		if (ret != -EOPNOTSUPP)
+			drm_err(dev, "Failed to register client: %d\n", ret);
+		else
+			ret = 0;
+
 		goto err_drm_client_init;
 	}
 
-- 
2.49.0