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From:   Paul Kocialkowski <contact@paulk.fr>
To:     dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Cc:     Maxime Ripard <maxime.ripard@bootlin.com>,
        David Airlie <airlied@linux.ie>, Chen-Yu Tsai <wens@csie.org>,
        linux-sunxi@googlegroups.com, Paul Kocialkowski <contact@paulk.fr>
Subject: [PATCH] drm/sun4i: Avoid failing to init fbdev without any connector
Date:   Tue,  7 Aug 2018 21:39:19 +0200
Message-Id: <20180807193919.4800-1-contact@paulk.fr>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Initializing and registering fbdev requires at least one DRM connector
and will fail otherwise. In order to support headless setups (for
instance for GPU rendering with the GBM backend, where a DRI card node
is required to provide GEM memory reservation), add a check on the
number of registered connectors before initializing fbdev.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
---
 drivers/gpu/drm/sun4i/sun4i_framebuffer.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_framebuffer.c b/drivers/gpu/drm/sun4i/sun4i_framebuffer.c
index 5f29850ef8ac..19a265e4a93a 100644
--- a/drivers/gpu/drm/sun4i/sun4i_framebuffer.c
+++ b/drivers/gpu/drm/sun4i/sun4i_framebuffer.c
@@ -49,6 +49,8 @@ static struct drm_mode_config_helper_funcs sun4i_de_mode_config_helpers = {
 
 int sun4i_framebuffer_init(struct drm_device *drm)
 {
+	int ret;
+
 	drm_mode_config_reset(drm);
 
 	drm->mode_config.max_width = 8192;
@@ -57,7 +59,13 @@ int sun4i_framebuffer_init(struct drm_device *drm)
 	drm->mode_config.funcs = &sun4i_de_mode_config_funcs;
 	drm->mode_config.helper_private = &sun4i_de_mode_config_helpers;
 
-	return drm_fb_cma_fbdev_init(drm, 32, 0);
+	if (drm->mode_config.num_connector > 0) {
+		ret = drm_fb_cma_fbdev_init(drm, 32, 0);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
 }
 
 void sun4i_framebuffer_free(struct drm_device *drm)
-- 
2.18.0