It adds an unpack only function for DRM infoframe for dynamic range and
mastering infoframe readout.
It unpacks the information data block contained in the binary buffer into
a structured frame of the HDMI Dynamic Range and Mastering (DRM)
information frame.

In contrast to hdmi_drm_infoframe_unpack() function, it does not verify
a checksum.

It can be used for unpacking a DP HDR Metadata Infoframe SDP case.
DP HDR Metadata Infoframe SDP uses the same Dynamic Range and Mastering
(DRM) information (CTA-861-G spec.) such as HDMI DRM infoframe.
But DP SDP header and payload structure are different from HDMI DRM
Infoframe. Therefore unpacking DRM infoframe for DP requires skipping of
a verifying checksum.

Signed-off-by: Gwan-gyeong Mun <gwan-gyeong....@intel.com>
Reviewed-by: Uma Shankar <uma.shan...@intel.com>
---
 drivers/video/hdmi.c | 58 +++++++++++++++++++++++++++++++-------------
 include/linux/hdmi.h |  2 ++
 2 files changed, 43 insertions(+), 17 deletions(-)

diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c
index 9c82e2a0a411..9818836d82b7 100644
--- a/drivers/video/hdmi.c
+++ b/drivers/video/hdmi.c
@@ -1775,20 +1775,18 @@ hdmi_vendor_any_infoframe_unpack(union 
hdmi_vendor_any_infoframe *frame,
 }
 
 /**
- * hdmi_drm_infoframe_unpack() - unpack binary buffer to a HDMI DRM infoframe
+ * hdmi_drm_infoframe_unpack_only() - unpack binary buffer to a HDMI DRM 
infoframe
  * @frame: HDMI DRM infoframe
  * @buffer: source buffer
  * @size: size of buffer
  *
- * Unpacks the information contained in binary @buffer into a structured
+ * Unpacks the information data block contained in binary @buffer into a 
structured
  * @frame of the HDMI Dynamic Range and Mastering (DRM) information frame.
- * Also verifies the checksum as required by section 5.3.5 of the HDMI 1.4
- * specification.
  *
  * Returns 0 on success or a negative error code on failure.
  */
-static int hdmi_drm_infoframe_unpack(struct hdmi_drm_infoframe *frame,
-                                    const void *buffer, size_t size)
+int hdmi_drm_infoframe_unpack_only(struct hdmi_drm_infoframe *frame,
+                                  const void *buffer, size_t size)
 {
        const u8 *ptr = buffer;
        const u8 *temp;
@@ -1797,23 +1795,13 @@ static int hdmi_drm_infoframe_unpack(struct 
hdmi_drm_infoframe *frame,
        int ret;
        int i;
 
-       if (size < HDMI_INFOFRAME_SIZE(DRM))
-               return -EINVAL;
-
-       if (ptr[0] != HDMI_INFOFRAME_TYPE_DRM ||
-           ptr[1] != 1 ||
-           ptr[2] != HDMI_DRM_INFOFRAME_SIZE)
-               return -EINVAL;
-
-       if (hdmi_infoframe_checksum(buffer, HDMI_INFOFRAME_SIZE(DRM)) != 0)
+       if (size < HDMI_DRM_INFOFRAME_SIZE)
                return -EINVAL;
 
        ret = hdmi_drm_infoframe_init(frame);
        if (ret)
                return ret;
 
-       ptr += HDMI_INFOFRAME_HEADER_SIZE;
-
        frame->eotf = ptr[0] & 0x7;
        frame->metadata_type = ptr[1] & 0x7;
 
@@ -1837,6 +1825,42 @@ static int hdmi_drm_infoframe_unpack(struct 
hdmi_drm_infoframe *frame,
 
        return 0;
 }
+EXPORT_SYMBOL(hdmi_drm_infoframe_unpack_only);
+
+/**
+ * hdmi_drm_infoframe_unpack() - unpack binary buffer to a HDMI DRM infoframe
+ * @frame: HDMI DRM infoframe
+ * @buffer: source buffer
+ * @size: size of buffer
+ *
+ * Unpacks the information contained in binary @buffer into a structured
+ * @frame of the HDMI Dynamic Range and Mastering (DRM) information frame.
+ * Also verifies the checksum as required by section 5.3.5 of the HDMI 1.4
+ * specification.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+static int hdmi_drm_infoframe_unpack(struct hdmi_drm_infoframe *frame,
+                                    const void *buffer, size_t size)
+{
+       const u8 *ptr = buffer;
+       int ret;
+
+       if (size < HDMI_INFOFRAME_SIZE(DRM))
+               return -EINVAL;
+
+       if (ptr[0] != HDMI_INFOFRAME_TYPE_DRM ||
+           ptr[1] != 1 ||
+           ptr[2] != HDMI_DRM_INFOFRAME_SIZE)
+               return -EINVAL;
+
+       if (hdmi_infoframe_checksum(buffer, HDMI_INFOFRAME_SIZE(DRM)) != 0)
+               return -EINVAL;
+
+       ret = hdmi_drm_infoframe_unpack_only(frame, ptr + 
HDMI_INFOFRAME_HEADER_SIZE,
+                                            size - HDMI_INFOFRAME_HEADER_SIZE);
+       return ret;
+}
 
 /**
  * hdmi_infoframe_unpack() - unpack binary buffer to a HDMI infoframe
diff --git a/include/linux/hdmi.h b/include/linux/hdmi.h
index 9918a6c910c5..afb43efc03e0 100644
--- a/include/linux/hdmi.h
+++ b/include/linux/hdmi.h
@@ -219,6 +219,8 @@ ssize_t hdmi_drm_infoframe_pack(struct hdmi_drm_infoframe 
*frame, void *buffer,
 ssize_t hdmi_drm_infoframe_pack_only(const struct hdmi_drm_infoframe *frame,
                                     void *buffer, size_t size);
 int hdmi_drm_infoframe_check(struct hdmi_drm_infoframe *frame);
+int hdmi_drm_infoframe_unpack_only(struct hdmi_drm_infoframe *frame,
+                                  const void *buffer, size_t size);
 
 enum hdmi_spd_sdi {
        HDMI_SPD_SDI_UNKNOWN,
-- 
2.25.0

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