drm/dp: Add backpointer to drm_device in drm_dp_aux
This is something that we've wanted for a while now: the ability to
actually look up the respective drm_device for a given drm_dp_aux struct.
This will also allow us to transition over to using the drm_dbg_*() helpers
for debug message printing, as we'll finally have a drm_device to reference
for doing so.
Note that there is one limitation with this - because some DP AUX adapters
exist as platform devices which are initialized independently of their
respective DRM devices, one cannot rely on drm_dp_aux->drm_dev to always be
non-NULL until drm_dp_aux_register() has been called. We make sure to point
this out in the documentation for struct drm_dp_aux.
v3:
* Add WARN_ON_ONCE() to drm_dp_aux_register() if drm_dev isn't filled out
Signed-off-by: Lyude Paul <lyude@redhat.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210423184309.207645-4-lyude@redhat.com
Reviewed-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 1e85c20..95efe37 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1840,6 +1840,8 @@ struct drm_dp_aux_cec {
* @name: user-visible name of this AUX channel and the I2C-over-AUX adapter
* @ddc: I2C adapter that can be used for I2C-over-AUX communication
* @dev: pointer to struct device that is the parent for this AUX channel
+ * @drm_dev: pointer to the &drm_device that owns this AUX channel. Beware, this
+ * may be %NULL before drm_dp_aux_register() has been called.
* @crtc: backpointer to the crtc that is currently using this AUX channel
* @hw_mutex: internal mutex used for locking transfers
* @crc_work: worker that captures CRCs for each frame
@@ -1847,7 +1849,11 @@ struct drm_dp_aux_cec {
* @transfer: transfers a message representing a single AUX transaction
*
* The @dev field should be set to a pointer to the device that implements the
- * AUX channel.
+ * AUX channel. As well, the @drm_dev field should be set to the &drm_device
+ * that will be using this AUX channel as early as possible. For many graphics
+ * drivers this should happen before drm_dp_aux_init(), however it's perfectly
+ * fine to set this field later so long as it's assigned before calling
+ * drm_dp_aux_register().
*
* The @name field may be used to specify the name of the I2C adapter. If set to
* %NULL, dev_name() of @dev will be used.
@@ -1879,6 +1885,7 @@ struct drm_dp_aux {
const char *name;
struct i2c_adapter ddc;
struct device *dev;
+ struct drm_device *drm_dev;
struct drm_crtc *crtc;
struct mutex hw_mutex;
struct work_struct crc_work;