[RFC] drm/fb: Propagate physical display dimensions to fbdev

[Daniel Vetter]

> Sun, Jul 30, 2017 at 11:11 PM, David Lechner <david at lechnology.com> wrote:
> fbdev has a place for the physical width and height of a display. I would
> like to have this information available to userspace. This patch works for me,
> but I have a strong suspicion that this is not the "right way".
>
> Any suggestions on how to get the proper struct drm_display_info here
> rather than assuming the first connector one is valid? I don't see an obvious
> way to do this.

This data can also change at runtime, which means we need to reprobe
it. And as you mention, we need to pick the data of the first
connected connector, not the very first connector the driver has. The
final connector loo in drm_setup_crtcs() would be a good place to do
that I think.
-Daniel

> ---
>  drivers/gpu/drm/drm_fb_helper.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 574af01..ff422da 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1768,8 +1768,14 @@ void drm_fb_helper_fill_var(struct fb_info *info, struct drm_fb_helper *fb_helpe
>         info->var.xoffset = 0;
>         info->var.yoffset = 0;
>         info->var.activate = FB_ACTIVATE_NOW;
> -       info->var.height = -1;
> -       info->var.width = -1;
> +
> +       if (fb_helper->connector_count) {
> +               info->var.height = fb_helper->connector_info[0]->connector->display_info.width_mm;
> +               info->var.width = fb_helper->connector_info[0]->connector->display_info.height_mm;
> +       } else {
> +               info->var.height = -1;
> +               info->var.width = -1;
> +       }
>
>         switch (fb->format->depth) {
>         case 8:
> --
> 2.7.4
>
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch