make fbdev/fbcon switchable per driver?

[Liviu Dudau]

On Fri, Jan 27, 2017 at 03:02:42PM +0100, Daniel Vetter wrote:
> On Fri, Jan 27, 2017 at 11:00:38AM +0100, Gerd Hoffmann wrote:
> >   Hi folks,
> > 
> > Problem at hand:  A virtual machine, equipped with two display devices,
> > one virtual, one physical (using pci pass-through, or kvmgt-based vgpu).
> > 
> > There is no easy way for the user to configure which of the two display
> > devices fbcon should run on.  i915 happens to win over bochs-drm or qxl,
> > so you can't use the emulated gfx device as text console.
> > 
> > One way out would be to add a module option to each driver, to turn off
> > fbdev emulation.  Attached patch does that for i915.
> > 
> > Comments?  Better ideas?
> 
> fbcon can be switched between different fbdev afaik, but don't ask me how.

Hint: Documentation/fb/fbcon.txt says fbcon=map:<ttynumbers>

Best regards,
Liviu

> I'd say if you want to keep fbcon (and not switch to something like
> kmscon), then that's where this logic should be. Might even exist already.
> Having a per-driver knob won't work, since then the next person complains
> about his multi-amd setup using the wrong gpu :-)
> -Daniel
> 
> > 
> > cheers,
> >   Gerd
> > 
> 
> > From 19236e412a6f0e9390c1ce77d8702bbdb5511174 Mon Sep 17 00:00:00 2001
> > From: Gerd Hoffmann <kraxel at redhat.com>
> > Date: Fri, 27 Jan 2017 08:05:40 +0100
> > Subject: [PATCH] drm i915: add fbdev option
> > 
> > Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
> > ---
> >  drivers/gpu/drm/i915/intel_fbdev.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> > index 3e3632c..cc0ba3e 100644
> > --- a/drivers/gpu/drm/i915/intel_fbdev.c
> > +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> > @@ -45,6 +45,11 @@
> >  #include <drm/i915_drm.h>
> >  #include "i915_drv.h"
> >  
> > +static bool enable_fbdev = true;
> > +module_param_named(fbdev, enable_fbdev, bool, 0600);
> > +MODULE_PARM_DESC(fbdev,
> > +		 "Enable legacy fbdev emulation [default=true]");
> > +
> >  static int intel_fbdev_set_par(struct fb_info *info)
> >  {
> >  	struct drm_fb_helper *fb_helper = info->par;
> > @@ -706,6 +711,9 @@ int intel_fbdev_init(struct drm_device *dev)
> >  	struct drm_i915_private *dev_priv = to_i915(dev);
> >  	int ret;
> >  
> > +	if (!enable_fbdev)
> > +		return 0;
> > +
> >  	if (WARN_ON(INTEL_INFO(dev)->num_pipes == 0))
> >  		return -ENODEV;
> >  
> > @@ -747,6 +755,8 @@ void intel_fbdev_initial_config_async(struct drm_device *dev)
> >  {
> >  	struct intel_fbdev *ifbdev = to_i915(dev)->fbdev;
> >  
> > +	if (!ifbdev)
> > +		return;
> >  	ifbdev->cookie = async_schedule(intel_fbdev_initial_config, ifbdev);
> >  }
> >  
> > -- 
> > 1.8.3.1
> > 
> 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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