ALSA: hda/hdmi: packet buffer index must be set before reading value

The check for infoframe transmit status in hdmi_infoframe_uptodate()
makes the assumption that packet buffer index is set to zero.

Align code with specification and explicitly set the index before
AC_VERB_GET_HDMI_DIP_XMIT. The packet index setting affects both
DIP-Data and DIP-XmitCtrl verbs.

There are no known cases where the old implementation has caused driver
to work incorrectly. This change is purely based on code review against
the specification (HDA spec rev1.0a).

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20201211131613.3271407-1-kai.vehmanen@linux.intel.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index 22f5a29..1e4a4b8 100644 (file)
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -638,11 +638,11 @@ static bool hdmi_infoframe_uptodate(struct hda_codec *codec, hda_nid_t pin_nid,
        u8 val;
        int i;
 
+       hdmi_set_dip_index(codec, pin_nid, 0x0, 0x0);
        if (snd_hda_codec_read(codec, pin_nid, 0, AC_VERB_GET_HDMI_DIP_XMIT, 0)
                                                            != AC_DIPXMIT_BEST)
                return false;
 
-       hdmi_set_dip_index(codec, pin_nid, 0x0, 0x0);
        for (i = 0; i < size; i++) {
                val = snd_hda_codec_read(codec, pin_nid, 0,
                                         AC_VERB_GET_HDMI_DIP_DATA, 0);