linux-kernel - Re: [PATCH 1/2] drm/vkms: Use index instead of 0 in possible crtc

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Date:   Mon, 17 Jun 2019 23:19:44 -0300
From:   Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>
To:     Brian Starkey <brian.starkey@....com>,
        Liviu Dudau <liviu.dudau@....com>,
        Haneen Mohammed <hamohammed.sa@...il.com>,
        Simon Ser <contact@...rsion.fr>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] drm/vkms: Use index instead of 0 in possible crtc

On 06/07, Daniel Vetter wrote:
> On Fri, Jun 07, 2019 at 11:37:55AM -0300, Rodrigo Siqueira wrote:
> > On Fri, Jun 7, 2019 at 4:40 AM Daniel Vetter <daniel@...ll.ch> wrote:
> > >
> > > On Thu, Jun 06, 2019 at 07:40:38PM -0300, Rodrigo Siqueira wrote:
> > > > When vkms calls drm_universal_plane_init(), it sets 0 for the
> > > > possible_crtcs parameter which works well for a single encoder and
> > > > connector; however, this approach is not flexible and does not fit well
> > > > for vkms. This commit adds an index parameter for vkms_plane_init()
> > > > which makes code flexible and enables vkms to support other DRM features.
> > > >
> > > > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>
> > >
> > > I think a core patch to WARN_ON if this is NULL would be good. Since
> > > that's indeed a bit broken ... We'd need to check all callers to make sure
> > > there's not other such bugs anywhere ofc.
> > > -Daniel
> > 
> > Do you mean add WARN_ON in `drm_universal_plane_init()` if
> > `possible_crtcs` is equal to zero?
> 
> Yeah, and same for endcoders I guess too. Altough with encoders I think
> there's a ton of broken drivers.

I made the patch, but when I started to write the commit message, I just
realized that I did not understand why possible_crtcs should not be
equal zero. Why can we not use zero?

> -Daniel
> 
> > 
> > > > ---
> > > >  drivers/gpu/drm/vkms/vkms_drv.c    | 2 +-
> > > >  drivers/gpu/drm/vkms/vkms_drv.h    | 4 ++--
> > > >  drivers/gpu/drm/vkms/vkms_output.c | 6 +++---
> > > >  drivers/gpu/drm/vkms/vkms_plane.c  | 4 ++--
> > > >  4 files changed, 8 insertions(+), 8 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> > > > index 738dd6206d85..92296bd8f623 100644
> > > > --- a/drivers/gpu/drm/vkms/vkms_drv.c
> > > > +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> > > > @@ -92,7 +92,7 @@ static int vkms_modeset_init(struct vkms_device *vkmsdev)
> > > >       dev->mode_config.max_height = YRES_MAX;
> > > >       dev->mode_config.preferred_depth = 24;
> > > >
> > > > -     return vkms_output_init(vkmsdev);
> > > > +     return vkms_output_init(vkmsdev, 0);
> > > >  }
> > > >
> > > >  static int __init vkms_init(void)
> > > > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > > > index 81f1cfbeb936..e81073dea154 100644
> > > > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > > > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > > > @@ -113,10 +113,10 @@ bool vkms_get_vblank_timestamp(struct drm_device *dev, unsigned int pipe,
> > > >                              int *max_error, ktime_t *vblank_time,
> > > >                              bool in_vblank_irq);
> > > >
> > > > -int vkms_output_init(struct vkms_device *vkmsdev);
> > > > +int vkms_output_init(struct vkms_device *vkmsdev, int index);
> > > >
> > > >  struct drm_plane *vkms_plane_init(struct vkms_device *vkmsdev,
> > > > -                               enum drm_plane_type type);
> > > > +                               enum drm_plane_type type, int index);
> > > >
> > > >  /* Gem stuff */
> > > >  struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
> > > > diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> > > > index 3b162b25312e..1442b447c707 100644
> > > > --- a/drivers/gpu/drm/vkms/vkms_output.c
> > > > +++ b/drivers/gpu/drm/vkms/vkms_output.c
> > > > @@ -36,7 +36,7 @@ static const struct drm_connector_helper_funcs vkms_conn_helper_funcs = {
> > > >       .get_modes    = vkms_conn_get_modes,
> > > >  };
> > > >
> > > > -int vkms_output_init(struct vkms_device *vkmsdev)
> > > > +int vkms_output_init(struct vkms_device *vkmsdev, int index)
> > > >  {
> > > >       struct vkms_output *output = &vkmsdev->output;
> > > >       struct drm_device *dev = &vkmsdev->drm;
> > > > @@ -46,12 +46,12 @@ int vkms_output_init(struct vkms_device *vkmsdev)
> > > >       struct drm_plane *primary, *cursor = NULL;
> > > >       int ret;
> > > >
> > > > -     primary = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_PRIMARY);
> > > > +     primary = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_PRIMARY, index);
> > > >       if (IS_ERR(primary))
> > > >               return PTR_ERR(primary);
> > > >
> > > >       if (enable_cursor) {
> > > > -             cursor = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_CURSOR);
> > > > +             cursor = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_CURSOR, index);
> > > >               if (IS_ERR(cursor)) {
> > > >                       ret = PTR_ERR(cursor);
> > > >                       goto err_cursor;
> > > > diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> > > > index 0e67d2d42f0c..20ffc52f9194 100644
> > > > --- a/drivers/gpu/drm/vkms/vkms_plane.c
> > > > +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> > > > @@ -168,7 +168,7 @@ static const struct drm_plane_helper_funcs vkms_primary_helper_funcs = {
> > > >  };
> > > >
> > > >  struct drm_plane *vkms_plane_init(struct vkms_device *vkmsdev,
> > > > -                               enum drm_plane_type type)
> > > > +                               enum drm_plane_type type, int index)
> > > >  {
> > > >       struct drm_device *dev = &vkmsdev->drm;
> > > >       const struct drm_plane_helper_funcs *funcs;
> > > > @@ -190,7 +190,7 @@ struct drm_plane *vkms_plane_init(struct vkms_device *vkmsdev,
> > > >               funcs = &vkms_primary_helper_funcs;
> > > >       }
> > > >
> > > > -     ret = drm_universal_plane_init(dev, plane, 0,
> > > > +     ret = drm_universal_plane_init(dev, plane, 1 << index,
> > > >                                      &vkms_plane_funcs,
> > > >                                      formats, nformats,
> > > >                                      NULL, type, NULL);
> > > > --
> > > > 2.21.0
> > >
> > >
> > >
> > > --
> > > Daniel Vetter
> > > Software Engineer, Intel Corporation
> > > http://blog.ffwll.ch
> > 
> > 
> > 
> > -- 
> > 
> > Rodrigo Siqueira
> > https://siqueira.tech
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Rodrigo Siqueira
https://siqueira.tech