video/hdmi: Constify infoframe passed to the pack functions

Let's make the infoframe pack functions usable with a const infoframe
structure. This allows us to precompute the infoframe earlier, and still
pack it later when we're no longer allowed to modify the structure.
So now we end up with a _check()+_pack_only() or _pack() functions
depending on whether you want to precompute the infoframes or not.
The names aren't great but I was lazy and didn't want to change all the
drivers.

v2: Deal with exynos churn
    Actually export the new funcs
v3: Fix various documentation fails (Hans)

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Cc: linux-media@vger.kernel.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180921143332.28970-1-ville.syrjala@linux.intel.comAcked-by: Hans Verkuil <hans.verkuil@cisco.com>

include/linux/hdmi.h

@@ -163,6 +163,9 @@ struct hdmi_avi_infoframe {
 int hdmi_avi_infoframe_init(struct hdmi_avi_infoframe *frame);
 ssize_t hdmi_avi_infoframe_pack(struct hdmi_avi_infoframe *frame, void *buffer,
 				size_t size);
+ssize_t hdmi_avi_infoframe_pack_only(const struct hdmi_avi_infoframe *frame,
+				     void *buffer, size_t size);
+int hdmi_avi_infoframe_check(struct hdmi_avi_infoframe *frame);
 
 enum hdmi_spd_sdi {
 	HDMI_SPD_SDI_UNKNOWN,
@@ -194,6 +197,9 @@ int hdmi_spd_infoframe_init(struct hdmi_spd_infoframe *frame,
 			    const char *vendor, const char *product);
 ssize_t hdmi_spd_infoframe_pack(struct hdmi_spd_infoframe *frame, void *buffer,
 				size_t size);
+ssize_t hdmi_spd_infoframe_pack_only(const struct hdmi_spd_infoframe *frame,
+				     void *buffer, size_t size);
+int hdmi_spd_infoframe_check(struct hdmi_spd_infoframe *frame);
 
 enum hdmi_audio_coding_type {
 	HDMI_AUDIO_CODING_TYPE_STREAM,
@@ -272,6 +278,9 @@ struct hdmi_audio_infoframe {
 int hdmi_audio_infoframe_init(struct hdmi_audio_infoframe *frame);
 ssize_t hdmi_audio_infoframe_pack(struct hdmi_audio_infoframe *frame,
 				  void *buffer, size_t size);
+ssize_t hdmi_audio_infoframe_pack_only(const struct hdmi_audio_infoframe *frame,
+				       void *buffer, size_t size);
+int hdmi_audio_infoframe_check(struct hdmi_audio_infoframe *frame);
 
 enum hdmi_3d_structure {
 	HDMI_3D_STRUCTURE_INVALID = -1,
@@ -299,6 +308,9 @@ struct hdmi_vendor_infoframe {
 int hdmi_vendor_infoframe_init(struct hdmi_vendor_infoframe *frame);
 ssize_t hdmi_vendor_infoframe_pack(struct hdmi_vendor_infoframe *frame,
 				   void *buffer, size_t size);
+ssize_t hdmi_vendor_infoframe_pack_only(const struct hdmi_vendor_infoframe *frame,
+					void *buffer, size_t size);
+int hdmi_vendor_infoframe_check(struct hdmi_vendor_infoframe *frame);
 
 union hdmi_vendor_any_infoframe {
 	struct {
@@ -330,8 +342,11 @@ union hdmi_infoframe {
 	struct hdmi_audio_infoframe audio;
 };
 
-ssize_t
-hdmi_infoframe_pack(union hdmi_infoframe *frame, void *buffer, size_t size);
+ssize_t hdmi_infoframe_pack(union hdmi_infoframe *frame, void *buffer,
+			    size_t size);
+ssize_t hdmi_infoframe_pack_only(const union hdmi_infoframe *frame,
+				 void *buffer, size_t size);
+int hdmi_infoframe_check(union hdmi_infoframe *frame);
 int hdmi_infoframe_unpack(union hdmi_infoframe *frame,
 			  const void *buffer, size_t size);
 void hdmi_infoframe_log(const char *level, struct device *dev,