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authorJani Nikula <jani.nikula@intel.com>2017-05-18 14:10:22 +0300
committerJani Nikula <jani.nikula@intel.com>2017-05-29 13:36:57 +0300
commit118b90f3f18e733c99f0e8b98ea31a815ffc4d14 (patch)
treec8a4302f16986bec4878eb1c014265821d5e1997 /drivers/gpu/drm/drm_dp_helper.c
parent5ed02dbb497422bf225783f46e6eadd237d23d6b (diff)
downloadlinux-118b90f3f18e733c99f0e8b98ea31a815ffc4d14.tar.xz
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
Diffstat (limited to 'drivers/gpu/drm/drm_dp_helper.c')
-rw-r--r--drivers/gpu/drm/drm_dp_helper.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 3e5f52110ea1..52e0ca9a5bb1 100644
--- 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);