[PATCH 2/5] drm/DP: Create pointer to generic DPCD access function

[Egbert Eich <eich@suse.de>]

This way a driver can replace this function with its own version.

Signed-off-by: Egbert Eich <eich@suse.de>
---
 drivers/gpu/drm/drm_dp_helper.c | 5 +++--
 include/drm/drm_dp_helper.h     | 8 ++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 959e207..d132838 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -238,7 +238,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
 			 void *buffer, size_t size)
 {
-	return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
+	return aux->dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
 				  size);
 }
 EXPORT_SYMBOL(drm_dp_dpcd_read);
@@ -260,7 +260,7 @@ EXPORT_SYMBOL(drm_dp_dpcd_read);
 ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
 			  void *buffer, size_t size)
 {
-	return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
+	return aux->dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
 				  size);
 }
 EXPORT_SYMBOL(drm_dp_dpcd_write);
@@ -552,6 +552,7 @@ static const struct i2c_algorithm drm_dp_i2c_algo = {
 int drm_dp_aux_register(struct drm_dp_aux *aux)
 {
 	mutex_init(&aux->hw_mutex);
+	aux->dpcd_access = drm_dp_dpcd_access;
 
 	aux->ddc.algo = &drm_dp_i2c_algo;
 	aux->ddc.algo_data = aux;
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 11f8c84..cd7b464 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -497,6 +497,8 @@ struct drm_dp_aux_msg {
  * @dev: pointer to struct device that is the parent for this AUX channel
  * @hw_mutex: internal mutex used for locking transfers
  * @transfer: transfers a message representing a single AUX transaction
+ * @dp_dpcd_access: hook to optionally wrap or replace high level dpcd message
+ *                  function.
  *
  * The .dev field should be set to a pointer to the device that implements
  * the AUX channel.
@@ -519,6 +521,10 @@ struct drm_dp_aux_msg {
  * transactions. The drm_dp_aux_register_i2c_bus() function registers an
  * I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers
  * should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter.
+ * dpcd_access() can be used by the driver to wrap or replace the generic
+ * dpcd access function in case certain operations should be performed before
+ * a dpcd transaction is started if this cannot reasonably performed in
+ * .transfer(). It is initialized to its default value by drm_dp_aux_register().
  *
  * Note that the aux helper code assumes that the .transfer() function
  * only modifies the reply field of the drm_dp_aux_msg structure.  The
@@ -531,6 +537,8 @@ struct drm_dp_aux {
 	struct mutex hw_mutex;
 	ssize_t (*transfer)(struct drm_dp_aux *aux,
 			    struct drm_dp_aux_msg *msg);
+	int (*dpcd_access)(struct drm_dp_aux *aux, u8 request,
+			     unsigned int offset, void *buffer, size_t size);
 	unsigned i2c_nack_count, i2c_defer_count;
 };
 
-- 
1.8.4.5

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