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

On Thu, Apr 26, 2018 at 10:07 AM, Jyri Sarha jsarha@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@ti.com Reviewed-by: Eric Anholt eric@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;
  
  

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