Read DisplayPort downstream port capabilities. Depending on
the DP port the capabilities are defined in length of 1 byte
or 4 bytes depending if the detailed capability information is
available.
Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 27 +++++++++++++++++++++++++++
include/drm/drm_dp_helper.h | 3 +++
2 files changed, 30 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index eeaf5a7..c4149fd 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -438,6 +438,33 @@ int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)
}
EXPORT_SYMBOL(drm_dp_link_configure);
+/**
+ * drm_dp_downstream_port_cap() - read downstream port capabilities
+ * @dpcd: DisplayPort configuration data
+ * @port_cap: port capabilities
+ *
+ * returns size of the port capabilites
+ */
+int drm_dp_downstream_port_cap(struct drm_dp_aux *aux,
+ const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+ u8 port_cap[4])
+{
+ int size;
+ bool detailed_cap_info = dpcd[DP_DOWNSTREAMPORT_PRESENT] &
+ DP_DETAILED_CAP_INFO_AVAILABLE;
+
+ if (detailed_cap_info) {
+ size = 4;
+ drm_dp_dpcd_read(aux, DP_DOWNSTREAM_PORT_0, port_cap, size);
+ } else {
+ size = 1;
+ drm_dp_dpcd_read(aux, DP_DOWNSTREAM_PORT_0, &port_cap[0], size);
+ }
+
+ return size;
+}
+EXPORT_SYMBOL(drm_dp_downstream_port_cap);
+
/*
* I2C-over-AUX implementation
*/
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index e384c7f..db8d3d47 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -806,6 +806,9 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);
int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link);
int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);
+int drm_dp_downstream_port_cap(struct drm_dp_aux *aux,
+ const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+ u8 port_cap[4]);
int drm_dp_aux_register(struct drm_dp_aux *aux);
void drm_dp_aux_unregister(struct drm_dp_aux *aux);
--
1.9.1
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