Re: [PATCH] drm: add locked variant of drm_fb_helper_force_kernel_mode

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Mon, 12 Apr 2010 10:05:00 +1000
Dave Airlie <airlied@gmail.com> wrote:

> On Sat, Apr 10, 2010 at 8:11 AM, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
> > Needed for panic and kdb, since we need to avoid taking the mode_config
> > mutex.
> 
> One comment below.
> 
> >
> > Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> > ---
> >  drivers/gpu/drm/drm_fb_helper.c |   42 +++++++++++++++++++++++++++++++++-----
> >  1 files changed, 36 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> > index 6929f5b..962eadb 100644
> > --- a/drivers/gpu/drm/drm_fb_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > @@ -242,18 +242,22 @@ static int drm_fb_helper_parse_command_line(struct drm_fb_helper *fb_helper)
> >        return 0;
> >  }
> >
> > -bool drm_fb_helper_force_kernel_mode(void)
> > +bool drm_fb_helper_force_kernel_mode_locked(void)
> >  {
> >        int i = 0;
> >        bool ret, error = false;
> >        struct drm_fb_helper *helper;
> > -
> > -       if (list_empty(&kernel_fb_helper_list))
> > -               return false;
> > +       struct drm_mode_set *mode_set;
> > +       struct drm_crtc *crtc;
> >
> >        list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) {
> >                for (i = 0; i < helper->crtc_count; i++) {
> > -                       struct drm_mode_set *mode_set = &helper->crtc_info[i].mode_set;
> > +                       mode_set = &helper->crtc_info[i].mode_set;
> > +                       crtc = helper->crtc_info[i].mode_set.crtc;
> > +
> > +                       if (!crtc->enabled)
> > +                               continue;
> > +
> >                        ret = drm_crtc_helper_set_config(mode_set);
> >                        if (ret)
> >                                error = true;
> > @@ -262,11 +266,37 @@ bool drm_fb_helper_force_kernel_mode(void)
> >        return error;
> >  }
> >
> > +bool drm_fb_helper_force_kernel_mode(void)
> > +{
> > +       bool ret;
> > +       struct drm_device *dev;
> > +       struct drm_fb_helper *helper;
> > +       struct drm_mode_set *mode_set;
> > +
> > +       if (list_empty(&kernel_fb_helper_list)) {
> > +               DRM_DEBUG_KMS("no fb helper list??\n");
> > +               return false;
> > +       }
> > +
> > +       /* Get the DRM device */
> > +       helper = list_first_entry(&kernel_fb_helper_list,
> > +                                 struct drm_fb_helper,
> > +                                 kernel_fb_list);
> > +       mode_set = &helper->crtc_info[0].mode_set;
> > +       dev = mode_set->crtc->dev;
> > +
> > +       mutex_lock(&dev->mode_config.mutex);
> > +       ret = drm_fb_helper_force_kernel_mode_locked();
> > +       mutex_unlock(&dev->mode_config.mutex);
> > +
> > +       return ret;
> > +}
> > +
> >  int drm_fb_helper_panic(struct notifier_block *n, unsigned long ununsed,
> >                        void *panic_str)
> >  {
> >        DRM_ERROR("panic occurred, switching back to text console\n");
> > -       return drm_fb_helper_force_kernel_mode();
> > +       drm_fb_helper_force_kernel_mode_locked();
> 
> Any reason to drop the return here?
> 
> not just remove the return 0?

Oh no; I don't think the return value is checked anywhere but we may as
well return it anyway.

-- 
Jesse Barnes, Intel Open Source Technology Center