linux-kernel - [PATCH 3.8 52/86] usb: Make DELAY_INIT quirk wait 100ms between Get Configuration requests

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Message-Id: <1396368519-12728-53-git-send-email-kamal@canonical.com>
Date:	Tue,  1 Apr 2014 09:08:05 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Julius Werner <jwerner@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.8 52/86] usb: Make DELAY_INIT quirk wait 100ms between Get Configuration requests

3.8.13.21 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Julius Werner <jwerner@...omium.org>

commit d86db25e53fa69e3e97f3b55dd82a70689787c5d upstream.

The DELAY_INIT quirk only reduces the frequency of enumeration failures
with the Logitech HD Pro C920 and C930e webcams, but does not quite
eliminate them. We have found that adding a delay of 100ms between the
first and second Get Configuration request makes the device enumerate
perfectly reliable even after several weeks of extensive testing. The
reasons for that are anyone's guess, but since the DELAY_INIT quirk
already delays enumeration by a whole second, wating for another 10th of
that isn't really a big deal for the one other device that uses it, and
it will resolve the problems with these webcams.

Signed-off-by: Julius Werner <jwerner@...omium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/usb/core/config.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index a6b2cab..62441e3 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -724,6 +724,10 @@ int usb_get_configuration(struct usb_device *dev)
 			result = -ENOMEM;
 			goto err;
 		}
+
+		if (dev->quirks & USB_QUIRK_DELAY_INIT)
+			msleep(100);
+
 		result = usb_get_descriptor(dev, USB_DT_CONFIG, cfgno,
 		    bigbuffer, length);
 		if (result < 0) {
-- 
1.8.3.2

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