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Subject[PATCH 2/6] ALSA: line6: Add delay before reading status
Date
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>
---
sound/usb/line6/driver.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index aac1e35..222c14f 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -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, u16 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, u16 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 |
--
2.1.0


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