Re: [PATCH/RFC 1/2] Add jack reporting API for ALSA
From: Takashi Iwai <hidden>
Date: 2008-05-30 08:15:46
Also in:
alsa-devel
At Thu, 29 May 2008 22:09:04 +0100, Mark Brown wrote:
Currently very few systems provide information about jack status to user space, even though many have hardware facilities to do detection. Those systems that do use an input device with the existing SW_HEADPHONE_INSERT switch type to do so, often independently of ALSA. This patch introduces a standard method for representing jacks to user space into ALSA. It allows drivers to register jacks for a sound card with the input subsystem, binding the input device to the card to help user space associate the input devices with their sound cards. The created input devices are named in the form "card longname jack" where jack is provided by the driver when allocating a jack. The existing user space API with SW_HEADPHONE_INSERT is preserved.
The implementation looks good, simple enough.
quoted hunk ↗ jump to hunk
diff --git a/sound/core/Kconfig b/sound/core/Kconfig index 829ca38..4e8e52d 100644 --- a/sound/core/Kconfig +++ b/sound/core/Kconfig@@ -16,6 +16,11 @@ config SND_RAWMIDI tristate depends on SND +config SND_JACK + tristate + depends on SND + depends on INPUT
If you suppose to "select" SND_JACK, depends have no meaning.
quoted hunk ↗ jump to hunk
diff --git a/sound/core/Makefile b/sound/core/Makefile index 5a01c76..e1cb6d6 100644 --- a/sound/core/Makefile +++ b/sound/core/Makefile@@ -20,9 +20,11 @@ snd-rawmidi-objs := rawmidi.o snd-timer-objs := timer.o snd-rtctimer-objs := rtctimer.o snd-hwdep-objs := hwdep.o +snd-jack-objs := jack.o obj-$(CONFIG_SND) += snd.o obj-$(CONFIG_SND_HWDEP) += snd-hwdep.o +obj-$(CONFIG_SND_JACK) += snd-jack.o
The code is small, and I don't see a big merit to make it a module.
+static int snd_jack_dev_register(struct snd_device *device)
+{
+ struct snd_jack *jack = device->device_data;
+ struct snd_card *card = device->card;
+ int err;
+
+ snprintf(jack->name, sizeof(jack->name), "%s %s",
+ card->longname, jack->id);The longname field could be sometimes really too long and verbose. I guess shortname would match better.
+int snd_jack_new(struct snd_card *card, const char *id, int type, + struct snd_jack **jjack)
(snip)
+ jack->input_dev->phys = "ALSA"; + jack->input_dev->dev.parent = card->dev;
The card->dev pointer might not be initialized always at this stage. You should check rather at register. Also, someone may want to pass a different device pointer for this. Passing struct device * to snd_jack_new would be an alternative. thanks, Takashi