ALSA: line6: Add delay before reading status (e64e94df) · Commits · 戴 / test

The device indicates the result of a read/write operation by making the status available on a subsequent request from the driver. This is not ready immediately, though, so the driver is currently slamming the device with hundreds of pointless requests before getting the expected response. Add a two millisecond delay before each attempt. This is approximately the behavior observed with version 4.2.7.1 of the Windows driver. Signed-off-by:

Chris Rorvick <chris@rorvick.com> Signed-off-by:

Takashi Iwai <tiwai@suse.de>

sound/usb/line6/driver.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -296,6 +296,8 @@ static void line6_data_received(struct urb *urb)
		line6_start_listen(line6);
		}

		#define LINE6_READ_WRITE_STATUS_DELAY 2 /* milliseconds */

		/*
		Read data from device.
		*/
		@@ -319,6 +321,8 @@ int line6_read_data(struct usb_line6 line6, int address, void data,

		/* Wait for data length. We'll get 0xff until length arrives. */
		do {
		mdelay(LINE6_READ_WRITE_STATUS_DELAY);

		ret = usb_control_msg(usbdev, usb_rcvctrlpipe(usbdev, 0), 0x67,
		USB_TYPE_VENDOR \| USB_RECIP_DEVICE \|
		USB_DIR_IN,
		@@ -376,6 +380,8 @@ int line6_write_data(struct usb_line6 line6, int address, void data,
		}

		do {
		mdelay(LINE6_READ_WRITE_STATUS_DELAY);

		ret = usb_control_msg(usbdev, usb_rcvctrlpipe(usbdev, 0),
		0x67,
		USB_TYPE_VENDOR \| USB_RECIP_DEVICE \|

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