ALSA: hda - hdmi: Protect ELD buffer

Because the eld buffer can be simultaneously accessed from both
workqueue context (updating) and process context (kcontrol read),
we need to protect it with a mutex to guarantee consistency.

To avoid holding the mutex while reading the ELD info from the
codec, we introduce a temporary eld buffer.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 39 insertions, 12 deletions

diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index 1e381918eb82..e77735d804a3 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -91,6 +91,7 @@ struct hdmi_spec {
         struct hda_pcm pcm_rec[MAX_HDMI_PINS];
         unsigned int channels_max; /* max over all cvts */
 
+        struct hdmi_eld temp_eld;
         /*
          * Non-generic ATI/NVIDIA specific
          */
@@ -352,7 +353,9 @@ static int hdmi_eld_ctl_info(struct snd_kcontrol *kcontrol,
         pin_idx = kcontrol->private_value;
         eld = &spec->pins[pin_idx].sink_eld;
 
+        mutex_lock(&eld->lock);
         uinfo->count = eld->eld_valid ? eld->eld_size : 0;
+        mutex_unlock(&eld->lock);
 
         return 0;
 }
@@ -368,7 +371,9 @@ static int hdmi_eld_ctl_get(struct snd_kcontrol *kcontrol,
         pin_idx = kcontrol->private_value;
         eld = &spec->pins[pin_idx].sink_eld;
 
+        mutex_lock(&eld->lock);
         if (eld->eld_size > ARRAY_SIZE(ucontrol->value.bytes.data)) {
+                mutex_unlock(&eld->lock);
                 snd_BUG();
                 return -EINVAL;
         }
@@ -378,6 +383,7 @@ static int hdmi_eld_ctl_get(struct snd_kcontrol *kcontrol,
         if (eld->eld_valid)
                 memcpy(ucontrol->value.bytes.data, eld->eld_buffer,
                        eld->eld_size);
+        mutex_unlock(&eld->lock);
 
         return 0;
 }
@@ -1164,7 +1170,9 @@ static int hdmi_read_pin_conn(struct hda_codec *codec, int pin_idx)
 static void hdmi_present_sense(struct hdmi_spec_per_pin *per_pin, int repoll)
 {
         struct hda_codec *codec = per_pin->codec;
-        struct hdmi_eld *eld = &per_pin->sink_eld;
+        struct hdmi_spec *spec = codec->spec;
+        struct hdmi_eld *eld = &spec->temp_eld;
+        struct hdmi_eld *pin_eld = &per_pin->sink_eld;
         hda_nid_t pin_nid = per_pin->pin_nid;
         /*
          * Always execute a GetPinSense verb here, even when called from
@@ -1175,38 +1183,56 @@ static void hdmi_present_sense(struct hdmi_spec_per_pin *per_pin, int repoll)
          * the unsolicited response to avoid custom WARs.
          */
         int present = snd_hda_pin_sense(codec, pin_nid);
-        bool eld_valid = false;
+        bool update_eld = false;
+        bool eld_changed = false;
 
-        eld->monitor_present    = !!(present & AC_PINSENSE_PRESENCE);
-        if (eld->monitor_present)
-                eld_valid       = !!(present & AC_PINSENSE_ELDV);
+        pin_eld->monitor_present = !!(present & AC_PINSENSE_PRESENCE);
+        if (pin_eld->monitor_present)
+                eld->eld_valid  = !!(present & AC_PINSENSE_ELDV);
+        else
+                eld->eld_valid = false;
 
         _snd_printd(SND_PR_VERBOSE,
                 "HDMI status: Codec=%d Pin=%d Presence_Detect=%d ELD_Valid=%d\n",
-                codec->addr, pin_nid, eld->monitor_present, eld_valid);
+                codec->addr, pin_nid, eld->monitor_present, eld->eld_valid);
 
-        eld->eld_valid = false;
-        if (eld_valid) {
+        if (eld->eld_valid) {
                 if (snd_hdmi_get_eld(codec, pin_nid, eld->eld_buffer,
                                                      &eld->eld_size) < 0)
-                        eld_valid = false;
+                        eld->eld_valid = false;
                 else {
                         memset(&eld->info, 0, sizeof(struct parsed_hdmi_eld));
                         if (snd_hdmi_parse_eld(&eld->info, eld->eld_buffer,
                                                     eld->eld_size) < 0)
-                                eld_valid = false;
+                                eld->eld_valid = false;
                 }
 
-                if (eld_valid) {
+                if (eld->eld_valid) {
                         snd_hdmi_show_eld(&eld->info);
-                        eld->eld_valid = true;
+                        update_eld = true;
                 }
                 else if (repoll) {
                         queue_delayed_work(codec->bus->workq,
                                            &per_pin->work,
                                            msecs_to_jiffies(300));
+                        return;
                 }
         }
+
+        mutex_lock(&pin_eld->lock);
+        if (pin_eld->eld_valid && !eld->eld_valid)
+                update_eld = true;
+        if (update_eld) {
+                pin_eld->eld_valid = eld->eld_valid;
+                eld_changed = memcmp(pin_eld->eld_buffer, eld->eld_buffer,
+                                     eld->eld_size) != 0;
+                if (eld_changed)
+                        memcpy(pin_eld->eld_buffer, eld->eld_buffer,
+                               eld->eld_size);
+                pin_eld->eld_size = eld->eld_size;
+                pin_eld->info = eld->info;
+        }
+        mutex_unlock(&pin_eld->lock);
 }
 
 static void hdmi_repoll_eld(struct work_struct *work)
@@ -1674,6 +1700,7 @@ static int generic_hdmi_init_per_pins(struct hda_codec *codec)
                 struct hdmi_eld *eld = &per_pin->sink_eld;
 
                 per_pin->codec = codec;
+                mutex_init(&eld->lock);
                 INIT_DELAYED_WORK(&per_pin->work, hdmi_repoll_eld);
                 snd_hda_eld_proc_new(codec, eld, pin_idx);
         }