[PATCH v4 2/2] drm/panel: Add device_link from panel device to drm device

[Daniel Vetter]

On Thu, Apr 26, 2018 at 10:07 AM, Jyri Sarha <jsarha at ti.com> wrote:
> Add device_link from panel device (supplier) to drm device (consumer)
> when drm_panel_attach() is called. This patch should protect the
> master drm driver if an attached panel driver unbinds while it is in
> use. The device_link should make sure the drm device is unbound before
> the panel driver becomes unavailable.
>
> The device_link is removed when drm_panel_detach() is called. The
> drm_panel_detach() should be called by the consumer DRM driver, not the
> panel driver, otherwise both drivers are racing to delete the same link.
>
> Signed-off-by: Jyri Sarha <jsarha at ti.com>
> Reviewed-by: Eric Anholt <eric at anholt.net>

Just noticed this complains when building docs:

./include/drm/drm_panel.h:98: warning: Function parameter or member
'link' not described in 'drm_panel'

Care to fix this? Also would be good to capture some of the
discussions that ensued from this patch in the docs ...

Thanks, Daniel

> ---
>  drivers/gpu/drm/drm_panel.c | 10 ++++++++++
>  include/drm/drm_panel.h     |  1 +
>  2 files changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> index 71e4075..965530a 100644
> --- a/drivers/gpu/drm/drm_panel.c
> +++ b/drivers/gpu/drm/drm_panel.c
> @@ -24,6 +24,7 @@
>  #include <linux/err.h>
>  #include <linux/module.h>
>
> +#include <drm/drm_device.h>
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_panel.h>
>
> @@ -104,6 +105,13 @@ int drm_panel_attach(struct drm_panel *panel, struct drm_connector *connector)
>         if (panel->connector)
>                 return -EBUSY;
>
> +       panel->link = device_link_add(connector->dev->dev, panel->dev, 0);
> +       if (!panel->link) {
> +               dev_err(panel->dev, "failed to link panel to %s\n",
> +                       dev_name(connector->dev->dev));
> +               return -EINVAL;
> +       }
> +
>         panel->connector = connector;
>         panel->drm = connector->dev;
>
> @@ -125,6 +133,8 @@ EXPORT_SYMBOL(drm_panel_attach);
>   */
>  int drm_panel_detach(struct drm_panel *panel)
>  {
> +       device_link_del(panel->link);
> +
>         panel->connector = NULL;
>         panel->drm = NULL;
>
> diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
> index 14ac240..26a1b5f 100644
> --- a/include/drm/drm_panel.h
> +++ b/include/drm/drm_panel.h
> @@ -89,6 +89,7 @@ struct drm_panel {
>         struct drm_device *drm;
>         struct drm_connector *connector;
>         struct device *dev;
> +       struct device_link *link;
>
>         const struct drm_panel_funcs *funcs;
>
> --
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch