[PATCH 3/3] ALSA: hda - Support deferred i915 audio component binding

Takashi Iwai
2016-04-07T10:57:31Z

Since we have the reliable way to detect the availability of i915
audio component, the HD-audio driver may wait for the binding safely.

This patch puts a simple completion call in the binding callback and
let snd_hdac_i915_init() waiting until the i915 component gets bound
or it notifies.

The wait for binding has a timeout of 60 seconds, in case where the
i915 module isn't present on the media by some reason. Such a
situation is rather the system error, but it's still safe to get a
timeout and indicate user about that.

The explicit call of request_module() is still kept in this patch in
order to avoid regression even for a system without the implicit
driver loading. But now it's called in the condition only when no ops
is found, so it's slightly optimized.

The pin-down of i915 module is still kept, too, as the dynamic
unbinding is still problematic. It may be racy and lead to the
refcount unbalance.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
sound/hda/hdac_i915.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/sound/hda/hdac_i915.c b/sound/hda/hdac_i915.c
index 812777f9af1f..6455d239a928 100644
--- a/sound/hda/hdac_i915.c
+++ b/sound/hda/hdac_i915.c
@@ -22,6 +22,7 @@
#include <sound/hda_i915.h>

static struct i915_audio_component *hdac_acomp;
+static DECLARE_COMPLETION(bind_comp);

/**
* snd_hdac_set_codec_wakeup - Enable / disable HDMI/DP codec wakeup
@@ -248,10 +249,12 @@ static int hdac_component_master_bind(struct device *dev)
goto out_unbind;
}

+ complete_all(&bind_comp);
return 0;

out_unbind:
component_unbind_all(dev, acomp);
+ complete_all(&bind_comp);

return ret;
}
@@ -339,6 +342,7 @@ int snd_hdac_i915_init(struct hdac_bus *bus)
return -ENOMEM;
bus->audio_component = acomp;
hdac_acomp = acomp;
+ init_completion(&bind_comp);

component_match_add(dev, &match, hdac_component_master_match, bus);
ret = component_master_add_with_match(dev, &hdac_component_master_ops,
@@ -346,12 +350,10 @@ int snd_hdac_i915_init(struct hdac_bus *bus)
if (ret < 0)
goto out_err;

- /*
- * Atm, we don't support deferring the component binding, so make sure
- * i915 is loaded and that the binding successfully completes.
- */
- request_module("i915");
+ if (!acomp->ops)
+ request_module("i915");

+ wait_for_completion_timeout(&bind_comp, msecs_to_jiffies(60 * 1000));
if (!acomp->ops || acomp->ops->disabled) {
ret = -ENODEV;
goto out_master_del;
--
2.8.1