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SubjectRe: Public ridicule due to sound/soc/soc-core.c abuse of the driver model
On Fri, Jan 06, 2012 at 08:50:36PM +0000, Russell King - ARM Linux wrote:
> I also disagree with your statement - I think it's quite simple to fix:
> 1. Change to using a flag to indicate whether the struct device is
> registered rather than ac97->dev.bus.

Looking at this deeper, you already have such a flag. It's called
codec->ac97_registered:

ret = soc_ac97_dev_register(rtd->codec);
if (ret < 0) {
printk(KERN_ERR "asoc: AC97 device register failed\n");
return ret;
}
rtd->codec->ac97_registered = 1;

static void soc_unregister_ac97_dai_link(struct snd_soc_codec *codec)
{
if (codec->ac97_registered) {
soc_ac97_dev_unregister(codec);
codec->ac97_registered = 0;
}
}
and soc_ac97_dev_{un,}register() do this:
static int soc_ac97_dev_unregister(struct snd_soc_codec *codec)
{
if (codec->ac97->dev.bus)
device_unregister(&codec->ac97->dev);
return 0;
}
static int soc_ac97_dev_register(struct snd_soc_codec *codec)
{
int err;
codec->ac97->dev.bus = &ac97_bus_type;
...
err = device_register(&codec->ac97->dev);
if (err < 0) {
...
codec->ac97->dev.bus = NULL;
return err;
}
return 0;
}

So, dev.bus is really duplicating what ac97_registered is doing and nothing
more, and I'd suggest that the very first patch cleaning up this buggy code
is to get rid of this duplication:

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index a25fa63..961f980 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -452,8 +452,7 @@ static inline void soc_cleanup_card_debugfs(struct snd_soc_card *card)
/* unregister ac97 codec */
static int soc_ac97_dev_unregister(struct snd_soc_codec *codec)
{
- if (codec->ac97->dev.bus)
- device_unregister(&codec->ac97->dev);
+ device_unregister(&codec->ac97->dev);
return 0;
}

@@ -474,7 +473,6 @@ static int soc_ac97_dev_register(struct snd_soc_codec *codec)
err = device_register(&codec->ac97->dev);
if (err < 0) {
snd_printk(KERN_ERR "Can't register ac97 bus\n");
- codec->ac97->dev.bus = NULL;
return err;
}
return 0;
Second patch would be to make soc_ac97_dev_unregister return type void -
it's pointless to have a function which always returns 0 and its return
value is never checked at its solitary call site.

Overall, it should look something like this (untested):

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index a25fa63..090b89e 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -448,33 +448,34 @@ static inline void soc_cleanup_card_debugfs(struct snd_soc_card *card)
}
#endif

+/* stop no dev release warning */
+static void soc_ac97_device_release(struct device *dev)
+{
+ struct snd_ac97 *ac97 = container_of(dev, snd_ac97, dev);
+
+ kfree(ac97);
+}
+
#ifdef CONFIG_SND_SOC_AC97_BUS
/* unregister ac97 codec */
static int soc_ac97_dev_unregister(struct snd_soc_codec *codec)
{
- if (codec->ac97->dev.bus)
- device_unregister(&codec->ac97->dev);
+ device_del(&codec->ac97->dev);
return 0;
}

-/* stop no dev release warning */
-static void soc_ac97_device_release(struct device *dev){}
-
/* register ac97 codec to bus */
static int soc_ac97_dev_register(struct snd_soc_codec *codec)
{
int err;

codec->ac97->dev.bus = &ac97_bus_type;
- codec->ac97->dev.parent = codec->card->dev;
- codec->ac97->dev.release = soc_ac97_device_release;

dev_set_name(&codec->ac97->dev, "%d-%d:%s",
codec->card->snd_card->number, 0, codec->name);
- err = device_register(&codec->ac97->dev);
+ err = device_add(&codec->ac97->dev);
if (err < 0) {
snd_printk(KERN_ERR "Can't register ac97 bus\n");
- codec->ac97->dev.bus = NULL;
return err;
}
return 0;
@@ -1748,9 +1749,13 @@ int snd_soc_new_ac97_codec(struct snd_soc_codec *codec,
return -ENOMEM;
}

+ device_initialize(&codec->ac97->dev);
+ codec->ac97->dev.parent = codec->card->dev;
+ codec->ac97->dev.release = soc_ac97_device_release;
+
codec->ac97->bus = kzalloc(sizeof(struct snd_ac97_bus), GFP_KERNEL);
if (codec->ac97->bus == NULL) {
- kfree(codec->ac97);
+ device_put(&codec->ac97->dev);
codec->ac97 = NULL;
mutex_unlock(&codec->mutex);
return -ENOMEM;
@@ -1783,7 +1788,7 @@ void snd_soc_free_ac97_codec(struct snd_soc_codec *codec)
soc_unregister_ac97_dai_link(codec);
#endif
kfree(codec->ac97->bus);
- kfree(codec->ac97);
+ device_put(&codec->ac97->dev);
codec->ac97 = NULL;
codec->ac97_created = 0;
mutex_unlock(&codec->mutex);


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