[PATCH v2 5/6] drm/bochs: Use shadow buffer for bochs framebuffer console

Thomas Zimmermann
Fri, 05 Jul 2019 09:26:12 -0000

The bochs driver (and virtual hardware) requires buffer objects to
reside in video ram to display them to the screen. So it can not
display the framebuffer console because the respective buffer object
is permanently pinned in system memory.

Using a shadow buffer for the console solves this problem. The console
emulation will pin the buffer object only during updates from the shadow
buffer. Otherwise, the bochs driver can freely relocated the buffer
between system memory and video ram.

v2:
	* select shadow FB via struct drm_mode_config.prefer_shadow_fbdev

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Acked-by: Noralf Tr?nnes <noralf at tronnes.org>
---
 drivers/gpu/drm/bochs/bochs_kms.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/bochs/bochs_kms.c
b/drivers/gpu/drm/bochs/bochs_kms.c
index bc19dbd531ef..359030d5d818 100644
--- a/drivers/gpu/drm/bochs/bochs_kms.c
+++ b/drivers/gpu/drm/bochs/bochs_kms.c
@@ -191,6 +191,7 @@ int bochs_kms_init(struct bochs_device *bochs)
 	bochs->dev->mode_config.fb_base = bochs->fb_base;
 	bochs->dev->mode_config.preferred_depth = 24;
 	bochs->dev->mode_config.prefer_shadow = 0;
+	bochs->dev->mode_config.prefer_shadow_fbdev = 1;
 	bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true;

 	bochs->dev->mode_config.funcs = &bochs_mode_funcs;
--
2.21.0