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Commit b099b969 authored by Takashi Iwai's avatar Takashi Iwai
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ALSA: usb-audio: Avoid superfluous usb_set_interface() calls 



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: default avatarTakashi Iwai <tiwai@suse.de>
parent 964af639

sound/usb/pcm.c

+4 −7
Original line number Diff line number Diff line
@@ -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);