drm/dp: add helper for reading DP sink/branch device desc from DPCD (118b90f3) · Commits · e / devices / android_kernel_fairphone_FP4

drivers/gpu/drm/drm_dp_helper.c

+35 −0

Original line number	Diff line number	Diff line
		@@ -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);

+19 −0

Original line number	Diff line number	Diff line
		@@ -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_ */