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ALSA: usb-audio: Avoid superfluous usb_set_interface() calls

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This is a preliminary change for the upcoming quirk implementation.

Currently USB-audio driver tries to call usb_set_interface() whenever
the format change with interface/altset modification happens.  In this
patch, the check is replaced with the comparison of cur_altsetting and
the targeted altsetting pointer, so that the driver may skip the
unnecessary function calls.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2018-05-02 09:36:28 +02:00
parent 964af639ad
commit b099b9693d
1 changed files with 4 additions and 7 deletions
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11
sound/usb/pcm.c
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@ -499,7 +499,7 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
iface = usb_ifnum_to_if(dev, fmt->iface);
if (WARN_ON(!iface))
return -EINVAL;
alts = &iface->altsetting[fmt->altset_idx];
alts = usb_altnum_to_altsetting(iface, fmt->altsetting);
altsd = get_iface_desc(alts);
if (WARN_ON(altsd->bAlternateSetting != fmt->altsetting))
return -EINVAL;
@ -521,9 +521,7 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
}
/* set interface */
if (subs->interface != fmt->iface ||
subs->altset_idx != fmt->altset_idx) {
if (iface->cur_altsetting != alts) {
err = snd_usb_select_mode_quirk(subs, fmt);
if (err < 0)
return -EIO;
@ -537,12 +535,11 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
}
dev_dbg(&dev->dev, "setting usb interface %d:%d\n",
fmt->iface, fmt->altsetting);
subs->interface = fmt->iface;
subs->altset_idx = fmt->altset_idx;
snd_usb_set_interface_quirk(dev);
}
subs->interface = fmt->iface;
subs->altset_idx = fmt->altset_idx;
subs->data_endpoint = snd_usb_add_endpoint(subs->stream->chip,
alts, fmt->endpoint, subs->direction,
SND_USB_ENDPOINT_TYPE_DATA);