Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752802AbbBKFEw (ORCPT ); Wed, 11 Feb 2015 00:04:52 -0500 Received: from mail-ie0-f170.google.com ([209.85.223.170]:36117 "EHLO mail-ie0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751006AbbBKFDj (ORCPT ); Wed, 11 Feb 2015 00:03:39 -0500 From: Chris Rorvick To: Takashi Iwai Cc: Chris Rorvick , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, Stefan Hajnoczi Subject: [PATCH 2/6] ALSA: line6: Add delay before reading status Date: Tue, 10 Feb 2015 23:03:13 -0600 Message-Id: <1423630997-25464-3-git-send-email-chris@rorvick.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1423630997-25464-1-git-send-email-chris@rorvick.com> References: <1423630997-25464-1-git-send-email-chris@rorvick.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1789 Lines: 52 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 --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/