drm/dp: add helper for reading DP sink/branch device desc from DPCD

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/acba54da7d80eafea9e59a893e27e3c31028c0ba.1495105635.git.jani.nikula@intel.com

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 3e5f52110ea17384c84f568ba9b1a4955922523c..52e0ca9a5bb1d0c5ebe809466f6ed67d2de61fc8 100644 (file)
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -1208,3 +1208,38 @@ int drm_dp_stop_crc(struct drm_dp_aux *aux)
        return 0;
 }
 EXPORT_SYMBOL(drm_dp_stop_crc);
+
+/**
+ * drm_dp_read_desc - read sink/branch descriptor from DPCD
+ * @aux: DisplayPort AUX channel
+ * @desc: Device decriptor to fill from DPCD
+ * @is_branch: true for branch devices, false for sink devices
+ *
+ * Read DPCD 0x400 (sink) or 0x500 (branch) into @desc. Also debug log the
+ * identification.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
+                    bool is_branch)
+{
+       struct drm_dp_dpcd_ident *ident = &desc->ident;
+       unsigned int offset = is_branch ? DP_BRANCH_OUI : DP_SINK_OUI;
+       int ret, dev_id_len;
+
+       ret = drm_dp_dpcd_read(aux, offset, ident, sizeof(*ident));
+       if (ret < 0)
+               return ret;
+
+       dev_id_len = strnlen(ident->device_id, sizeof(ident->device_id));
+
+       DRM_DEBUG_KMS("DP %s: OUI %*phD dev-ID %*pE HW-rev %d.%d SW-rev %d.%d\n",
+                     is_branch ? "branch" : "sink",
+                     (int)sizeof(ident->oui), ident->oui,
+                     dev_id_len, ident->device_id,
+                     ident->hw_rev >> 4, ident->hw_rev & 0xf,
+                     ident->sw_major_rev, ident->sw_minor_rev);
+
+       return 0;
+}
+EXPORT_SYMBOL(drm_dp_read_desc);

diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index c0bd0d7651a947bf06407d7c680dde5c377b9b26..84502da177a1681a6c7ac4b2b838e362bd24bc4d 100644 (file)
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -913,4 +913,23 @@ void drm_dp_aux_unregister(struct drm_dp_aux *aux);
 int drm_dp_start_crc(struct drm_dp_aux *aux, struct drm_crtc *crtc);
 int drm_dp_stop_crc(struct drm_dp_aux *aux);
 
+struct drm_dp_dpcd_ident {
+       u8 oui[3];
+       u8 device_id[6];
+       u8 hw_rev;
+       u8 sw_major_rev;
+       u8 sw_minor_rev;
+} __packed;
+
+/**
+ * struct drm_dp_desc - DP branch/sink device descriptor
+ * @ident: DP device identification from DPCD 0x400 (sink) or 0x500 (branch).
+ */
+struct drm_dp_desc {
+       struct drm_dp_dpcd_ident ident;
+};
+
+int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
+                    bool is_branch);
+
 #endif /* _DRM_DP_HELPER_H_ */