Re: [RFC 1/6] drm: Add top level Kconfig option for DRM fbdev emulation
From: Archit Taneja
Date: Fri Mar 13 2015 - 07:00:23 EST
On 03/13/2015 02:36 PM, Daniel Vetter wrote:
On Fri, Mar 13, 2015 at 11:55:07AM +0530, Archit Taneja wrote:
On 03/11/2015 08:47 PM, Daniel Vetter wrote:
On Wed, Mar 11, 2015 at 01:51:02PM +0530, Archit Taneja wrote:
On 03/10/2015 05:47 PM, Daniel Vetter wrote:
On Tue, Mar 10, 2015 at 03:52:41PM +0530, Archit Taneja wrote:
On 03/10/2015 03:35 PM, Daniel Vetter wrote:
On Tue, Mar 10, 2015 at 03:22:49PM +0530, Archit Taneja wrote:
On 03/10/2015 03:17 PM, Daniel Vetter wrote:
On Tue, Mar 10, 2015 at 03:11:28PM +0530, Archit Taneja wrote:
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 151a050..38f83a0 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -40,6 +40,24 @@ config DRM_KMS_FB_HELPER
help
FBDEV helpers for KMS drivers.
+config DRM_FBDEV_EMULATION
+ bool "Enable legacy fbdev support for your modesetting driver"
+ depends on DRM
+ select DRM_KMS_HELPER
+ select DRM_KMS_FB_HELPER
+ select FB_SYS_FILLRECT
+ select FB_SYS_COPYAREA
+ select FB_SYS_IMAGEBLIT
+ select FB_SYS_FOPS
+ select FB_CFB_FILLRECT
+ select FB_CFB_COPYAREA
+ select FB_CFB_IMAGEBLIT
+ default y
+ help
+ Choose this option if you have a need for the legacy fbdev
+ support. Note that this support also provide the linux console
+ support on top of your modesetting driver.
Maybe clarify that for linux console support you also need
CONFIG_FRAMEBUFFER_CONSOLE? fbdev alone isn't enough.
DRM_KMS_FB_HELPER selects that for us, right?
Hm right I've missed that. Reminds me that you need one more patch at the
end to remove all the various select DRM_KMS_FB_HELPER from all drm
drivers. Otherwise this knob here won't work by default if you e.g. select
radeon. In general we can't mix explicit options with menu entries with a
select.
I was trying that out. Removing DRM_KMS_FB_HELPER and having
DRM_FBDEV_EMULATION disabled breaks drivers which use FB stuff internally in
their respective xyz_fbdev.c files.
But with the stubbed out functions that should work, right? Why doesn't
it?
There are still calls to functions from fb core like fb_set_suspend and
register_framebuffer which aren't covered by the drm fb helper functions.
Hm, sounds like we need another patch to stub out fb_set_suspend when
fbdev isn't enabled. Is there anything else?
There are a handful of fb core functions which are called by drm drivers:
fb_alloc_cmap/fb_dealloc_cmap
fb_sys_read/fb_sys_write
register_framebuffer/unregister_framebuffer/unlink_framebuffer/
remove_conflicting_framebuffers
fb_set_suspend
fb_deferred_io_init/fb_deferred_io_cleanup
framebuffer_alloc/framebuffer_release
Hm yeah that's somewhat annoying indeed. What about the following:
1. We move all the #include <linux/fb.h> from drivers into drm_fb_helper.h
2. Then we add stubs for these functions in drm_fb_helper.h, like this
#if defined(CONFIG_FB)
#include <linux/fb.h>
#else
/* static inline stubs for all the fb stuff used by kms drivers */
#endif
Imo this makes sense since kms drivers really have a bit a special
situation with fbdev. They're not full-blown fbdev drivers and can be
useful fully without fbdev.
What do you think?
This looks good! I'll give it a try.
Archit
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/