linux-kernel - [PATCH] load fbcon from drm_kms

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Date:	Sat, 11 Dec 2010 15:05:48 -0600
From:	David Fries <david@...es.net>
To:	linux-kernel@...r.kernel.org
Cc:	David Airlie <airlied@...ux.ie>, dri-devel@...ts.freedesktop.org
Subject: [PATCH] load fbcon from drm_kms_helper

Kconfig says fbcon is required by drm_kms_helper.  If radeon, fbcon,
and drm_kms_helper are all modules, radeon is auto loaded (by PCI id?),
drm_kms_helper is loaded because of the module dependency, but fbcon
isn't loaded leaving the console unusable.  Since fbcon is required
and there isn't an explicit module dependency, request the module
to be loaded from drm_kms_helper.

Signed-off-by: David Fries <david@...es.net>
Cc: David Airlie <airlied@...ux.ie>
Cc: dri-devel@...ts.freedesktop.org
---
This solves compiling CONFIG_FB=m and being left with a blank screen
because the radeon module is automatically loaded, but fbcon isn't.
If radeon had to be manually loaded, then it would be the user's fault for
not loading fbcon as well, but as radeon is being loaded automatically,
there isn't much a user can do from console to even fix it.  More bug
details from here,
https://bugzilla.kernel.org/show_bug.cgi?id=16221

Does this look like a reasonable solution?  Should it bother checking
find_module first?

 drivers/gpu/drm/drm_fb_helper.c |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index d2849e4..dd1e726 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1530,3 +1530,24 @@ bool drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
 }
 EXPORT_SYMBOL(drm_fb_helper_hotplug_event);
 
+/* The Kconfig DRM_KMS_HELPER selects FRAMEBUFFER_CONSOLE (if !EMBEDDED)
+ * but the module doesn't depend on any fb console symbols.  At least
+ * attempt to load fbcon to avoid leaving the system without a usable console.
+ */
+#if defined(CONFIG_FRAMEBUFFER_CONSOLE_MODULE) && !defined(CONFIG_EMBEDDED)
+static int __init drm_fb_helper_modinit(void)
+{
+	const char *namue = "fbcon";
+	struct module *fbcon;
+
+	mutex_lock(&module_mutex);
+	fbcon = find_module(name);
+	mutex_unlock(&module_mutex);
+
+	if (!fbcon)
+		request_module_nowait(name);
+	return 0;
+}
+
+module_init(drm_fb_helper_modinit);
+#endif
-- 
1.7.2.3

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