Re: [alsa-devel] [PATCH v4 4/5] ALSA: hda - hdmi: Protect ELD buffer

At Tue, 19 Feb 2013 13:23:04 +0100, David Henningsson wrote:

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

Looks almost good to me.

One remaining question is whether we should copy the data when the probe is being repolled. During repolling, it's essentially an "unknown" state: the display is detected, but ELD isn't. Since you'll very get a valid ELD soon later, wouldn't it be better to just postpone the update / copy of eld to pin_eld until the successful repoll? i.e. simply add "return" after queue_delayed_work().

thanks,

Takashi

---

sound/pci/hda/hda_eld.c | 8 ++++++- sound/pci/hda/hda_local.h | 1 + sound/pci/hda/patch_hdmi.c | 50 +++++++++++++++++++++++++++++++++----------- 3 files changed, 46 insertions(+), 13 deletions(-)

diff --git a/sound/pci/hda/hda_eld.c b/sound/pci/hda/hda_eld.c index 16066d7..7dd8463 100644 --- a/sound/pci/hda/hda_eld.c +++ b/sound/pci/hda/hda_eld.c @@ -500,10 +500,13 @@ static void hdmi_print_eld_info(struct snd_info_entry *entry, [4 ... 7] = "reserved" };

• mutex_lock(&eld->lock); snd_iprintf(buffer, "monitor_present\t\t%d\n", eld->monitor_present); snd_iprintf(buffer, "eld_valid\t\t%d\n", eld->eld_valid);

• if (!eld->eld_valid)

• if (!eld->eld_valid) {

• mutex_unlock(&eld->lock);
  

  return;
• } snd_iprintf(buffer, "monitor_name\t\t%s\n", e->monitor_name); snd_iprintf(buffer, "connection_type\t\t%s\n", eld_connection_type_names[e->conn_type]);

@@ -525,6 +528,7 @@ static void hdmi_print_eld_info(struct snd_info_entry *entry,

for (i = 0; i < e->sad_count; i++) hdmi_print_sad_info(i, e->sad + i, buffer);

• mutex_unlock(&eld->lock);

}

static void hdmi_write_eld_info(struct snd_info_entry *entry, @@ -538,6 +542,7 @@ static void hdmi_write_eld_info(struct snd_info_entry *entry, long long val; unsigned int n;

• mutex_lock(&eld->lock); while (!snd_info_get_line(buffer, line, sizeof(line))) { if (sscanf(line, "%s %llx", name, &val) != 2) continue;

@@ -589,6 +594,7 @@ static void hdmi_write_eld_info(struct snd_info_entry *entry, e->sad_count = n + 1; } }

• mutex_unlock(&eld->lock);

}

diff --git a/sound/pci/hda/hda_local.h b/sound/pci/hda/hda_local.h index 363cd48..83b7486 100644 --- a/sound/pci/hda/hda_local.h +++ b/sound/pci/hda/hda_local.h @@ -739,6 +739,7 @@ struct hdmi_eld { int eld_size; char eld_buffer[ELD_MAX_SIZE]; struct parsed_hdmi_eld info;

• struct mutex lock;

#ifdef CONFIG_PROC_FS struct snd_info_entry *proc_entry; #endif diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c index d157528..ec3ff3f 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; }

@@ -376,6 +381,7 @@ 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;

} @@ -1162,7 +1168,9 @@ 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

@@ -1173,31 +1181,33 @@ 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,

@@ -1205,6 +1215,21 @@ static void hdmi_present_sense(struct hdmi_spec_per_pin *per_pin, int repoll) msecs_to_jiffies(300)); } }

• 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) @@ -1672,6 +1697,7 @@ 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); }

-- 1.7.9.5

---

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