Hi Takashi,
On 9/7/2023 8:36 AM, Takashi Iwai wrote:
On Tue, 29 Aug 2023 23:06:36 +0200,
Wesley Cheng wrote:
Allow for different platforms to be notified on USB SND connect/disconnect
seqeunces. This allows for platform USB SND modules to properly initialize
and populate internal structures with references to the USB SND chip
device.
Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
---
sound/usb/card.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
sound/usb/card.h | 9 +++++++++
2 files changed, 54 insertions(+)
diff --git a/sound/usb/card.c b/sound/usb/card.c
index 1b2edc0fd2e9..067a1e82f4bf 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -118,6 +118,34 @@ MODULE_PARM_DESC(skip_validation, "Skip unit descriptor validation (default: no)
static DEFINE_MUTEX(register_mutex);
static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
static struct usb_driver usb_audio_driver;
+static struct snd_usb_platform_ops *platform_ops;
+
+int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops)
+{
+ int ret;
+
+ mutex_lock(®ister_mutex);
+ if (platform_ops) {
+ ret = -EEXIST;
+ goto out;
+ }
+
+ platform_ops = ops;
+out:
+ mutex_unlock(®ister_mutex);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(snd_usb_register_platform_ops);
For adding this kind of API, please give the proper comment.
Especially this API is special and need a caution, to mention that it
can be used only for a single instance.
Also, it should be mentioned that all callbacks are exclusive under
the global register_mutex.
Thanks for taking the time to review. Sure, I'll add some comments in
these new APIs to document what they are used for and how they are
protected and limited.
@@ -910,7 +938,11 @@ static int usb_audio_probe(struct usb_interface *intf,
chip->num_interfaces++;
usb_set_intfdata(intf, chip);
atomic_dec(&chip->active);
+
+ if (platform_ops && platform_ops->connect_cb)
+ platform_ops->connect_cb(chip);
mutex_unlock(®ister_mutex);
One uncertain thing is the argument for connect_cb and disconnect_cb.
Those take snd_usb_audio object, but the callback gets called per
interface at each probe and disconnect. How does the callee handle
multiple calls?
I guess it should depend on how the platform driver wants to handle it?
I haven't run into a device with multiple UAC interfaces before, so
I'll need to mimic this configuration on a device, so I can see how it
exposes itself.
Will investigate this a bit more on my end and come back with my findings.
Last but not least, the patch subject should be with "ALSA:" prefix,
and in this case, at best "ALSA: usb-audio: xxx".
Got it, thanks!
Thanks
Wesley Cheng
