Commit b96681bd authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: usb-audio: Initialize every feature unit once at probe time 



So far we used to read the current value of the mixer element
dynamically at the first access, and the error from a GET_CUR message
is treated as a fatal error (unless QUIRK_IGNORE_CTL_ERROR is set).
It's rather inconvenient, as most of GET_CUR errors are no fatal, and
we can continue operation with assumption of some fixed value.

This patch makes the USB-audio driver to change the behavior at probe
time; now it tries to initialize the current value of each mixer
element that is built from a feature unit (those for typically for
mixer volumes and switches).  When a read failure happens, it tries to
set the known minimum value.  After that point, a cached value is used
always, hence we won't hit GET_CUR message error any longer.

The error from GET_CUR message is still shown as a warning normally,
but only once at the probe time, and it'll keep operating.  If the
message is confirmed to be harmless, it can be shut up by
QUIRK_IGNORE_CTL_ERROR quirk flag, too.

Tested-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20211014130636.17860-4-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 509975c7

sound/usb/mixer.c

+33 −1
Original line number Diff line number Diff line
@@ -1199,12 +1199,32 @@ static void volume_control_quirks(struct usb_mixer_elem_info *cval, 
	}

}



/* forcibly initialize the current mixer value; if GET_CUR fails, set to

 * the minimum as default

 */

static void init_cur_mix_raw(struct usb_mixer_elem_info *cval, int ch, int idx)

{

	int val, err;



	err = snd_usb_get_cur_mix_value(cval, ch, idx, &val);

	if (!err)

		return;

	if (!cval->head.mixer->ignore_ctl_error)

		usb_audio_warn(cval->head.mixer->chip,

			       "%d:%d: failed to get current value for ch %d (%d)\n",

			       cval->head.id, mixer_ctrl_intf(cval->head.mixer),

			       ch, err);

	snd_usb_set_cur_mix_value(cval, ch, idx, cval->min);

}



/*

 * retrieve the minimum and maximum values for the specified control

 */

static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,

				   int default_min, struct snd_kcontrol *kctl)

{

	int i, idx;



	/* for failsafe */

	cval->min = default_min;

	cval->max = cval->min + 1;
@@ -1217,7 +1237,6 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval, 
	} else {

		int minchn = 0;

		if (cval->cmask) {

			int i;

			for (i = 0; i < MAX_CHANNELS; i++)

				if (cval->cmask & (1 << i)) {

					minchn = i + 1;
@@ -1318,6 +1337,19 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval, 
		}

	}



	/* initialize all elements */

	if (!cval->cmask) {

		init_cur_mix_raw(cval, 0, 0);

	} else {

		idx = 0;

		for (i = 0; i < MAX_CHANNELS; i++) {

			if (cval->cmask & (1 << i)) {

				init_cur_mix_raw(cval, i + 1, idx);

				idx++;

			}

		}

	}



	return 0;

}