<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/drivers/usb/class, branch v4.9.207</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>USB: usblp: fix use-after-free on disconnect</title>
<updated>2019-10-29T08:15:17+00:00</updated>
<author>
<name>Johan Hovold</name>
<email>johan@kernel.org</email>
</author>
<published>2019-10-15T17:55:22+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=e5e48d279fce3d6536b0f70c786f7e98d8f84e1c'/>
<id>e5e48d279fce3d6536b0f70c786f7e98d8f84e1c</id>
<content type='text'>
commit 7a759197974894213621aa65f0571b51904733d6 upstream.

A recent commit addressing a runtime PM use-count regression, introduced
a use-after-free by not making sure we held a reference to the struct
usb_interface for the lifetime of the driver data.

Fixes: 9a31535859bf ("USB: usblp: fix runtime PM after driver unbind")
Cc: stable &lt;stable@vger.kernel.org&gt;
Reported-by: syzbot+cd24df4d075c319ebfc5@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold &lt;johan@kernel.org&gt;
Link: https://lore.kernel.org/r/20191015175522.18490-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 7a759197974894213621aa65f0571b51904733d6 upstream.

A recent commit addressing a runtime PM use-count regression, introduced
a use-after-free by not making sure we held a reference to the struct
usb_interface for the lifetime of the driver data.

Fixes: 9a31535859bf ("USB: usblp: fix runtime PM after driver unbind")
Cc: stable &lt;stable@vger.kernel.org&gt;
Reported-by: syzbot+cd24df4d075c319ebfc5@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold &lt;johan@kernel.org&gt;
Link: https://lore.kernel.org/r/20191015175522.18490-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>USB: usblp: fix runtime PM after driver unbind</title>
<updated>2019-10-17T20:42:36+00:00</updated>
<author>
<name>Johan Hovold</name>
<email>johan@kernel.org</email>
</author>
<published>2019-10-01T08:49:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=25184b8618959d6082b30f3e8318ffc467426e40'/>
<id>25184b8618959d6082b30f3e8318ffc467426e40</id>
<content type='text'>
commit 9a31535859bfd8d1c3ed391f5e9247cd87bb7909 upstream.

Since commit c2b71462d294 ("USB: core: Fix bug caused by duplicate
interface PM usage counter") USB drivers must always balance their
runtime PM gets and puts, including when the driver has already been
unbound from the interface.

Leaving the interface with a positive PM usage counter would prevent a
later bound driver from suspending the device.

Fixes: c2b71462d294 ("USB: core: Fix bug caused by duplicate interface PM usage counter")
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Johan Hovold &lt;johan@kernel.org&gt;
Link: https://lore.kernel.org/r/20191001084908.2003-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 9a31535859bfd8d1c3ed391f5e9247cd87bb7909 upstream.

Since commit c2b71462d294 ("USB: core: Fix bug caused by duplicate
interface PM usage counter") USB drivers must always balance their
runtime PM gets and puts, including when the driver has already been
unbound from the interface.

Leaving the interface with a positive PM usage counter would prevent a
later bound driver from suspending the device.

Fixes: c2b71462d294 ("USB: core: Fix bug caused by duplicate interface PM usage counter")
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Johan Hovold &lt;johan@kernel.org&gt;
Link: https://lore.kernel.org/r/20191001084908.2003-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>USB: cdc-wdm: fix race between write and disconnect due to flag abuse</title>
<updated>2019-09-06T08:19:48+00:00</updated>
<author>
<name>Oliver Neukum</name>
<email>oneukum@suse.com</email>
</author>
<published>2019-08-27T10:34:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7189b43f9280cdfa015f8f26b2c5cab89ffd9e4b'/>
<id>7189b43f9280cdfa015f8f26b2c5cab89ffd9e4b</id>
<content type='text'>
commit 1426bd2c9f7e3126e2678e7469dca9fd9fc6dd3e upstream.

In case of a disconnect an ongoing flush() has to be made fail.
Nevertheless we cannot be sure that any pending URB has already
finished, so although they will never succeed, they still must
not be touched.
The clean solution for this is to check for WDM_IN_USE
and WDM_DISCONNECTED in flush(). There is no point in ever
clearing WDM_IN_USE, as no further writes make sense.

The issue is as old as the driver.

Fixes: afba937e540c9 ("USB: CDC WDM driver")
Reported-by: syzbot+d232cca6ec42c2edb3fc@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Link: https://lore.kernel.org/r/20190827103436.21143-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 1426bd2c9f7e3126e2678e7469dca9fd9fc6dd3e upstream.

In case of a disconnect an ongoing flush() has to be made fail.
Nevertheless we cannot be sure that any pending URB has already
finished, so although they will never succeed, they still must
not be touched.
The clean solution for this is to check for WDM_IN_USE
and WDM_DISCONNECTED in flush(). There is no point in ever
clearing WDM_IN_USE, as no further writes make sense.

The issue is as old as the driver.

Fixes: afba937e540c9 ("USB: CDC WDM driver")
Reported-by: syzbot+d232cca6ec42c2edb3fc@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Link: https://lore.kernel.org/r/20190827103436.21143-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>usb: cdc-acm: make sure a refcount is taken early enough</title>
<updated>2019-08-25T08:51:49+00:00</updated>
<author>
<name>Oliver Neukum</name>
<email>oneukum@suse.com</email>
</author>
<published>2019-08-08T14:21:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=fccd6134d5addf2be1407e3250efdc854b5c5d8a'/>
<id>fccd6134d5addf2be1407e3250efdc854b5c5d8a</id>
<content type='text'>
commit c52873e5a1ef72f845526d9f6a50704433f9c625 upstream.

destroy() will decrement the refcount on the interface, so that
it needs to be taken so early that it never undercounts.

Fixes: 7fb57a019f94e ("USB: cdc-acm: Fix potential deadlock (lockdep warning)")
Cc: stable &lt;stable@vger.kernel.org&gt;
Reported-and-tested-by: syzbot+1b2449b7b5dc240d107a@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Link: https://lore.kernel.org/r/20190808142119.7998-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit c52873e5a1ef72f845526d9f6a50704433f9c625 upstream.

destroy() will decrement the refcount on the interface, so that
it needs to be taken so early that it never undercounts.

Fixes: 7fb57a019f94e ("USB: cdc-acm: Fix potential deadlock (lockdep warning)")
Cc: stable &lt;stable@vger.kernel.org&gt;
Reported-and-tested-by: syzbot+1b2449b7b5dc240d107a@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Link: https://lore.kernel.org/r/20190808142119.7998-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>usb: cdc-acm: send ZLP for Telit 3G Intel based modems</title>
<updated>2019-01-16T21:12:31+00:00</updated>
<author>
<name>Daniele Palmas</name>
<email>dnlplm@gmail.com</email>
</author>
<published>2018-12-28T15:15:41+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=6fffa14699e77020ca5635a36a3b37357a44c123'/>
<id>6fffa14699e77020ca5635a36a3b37357a44c123</id>
<content type='text'>
commit 34aabf918717dd14e05051896aaecd3b16b53d95 upstream.

Telit 3G Intel based modems require zero packet to be sent if
out data size is equal to the endpoint max packet size.

Signed-off-by: Daniele Palmas &lt;dnlplm@gmail.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 34aabf918717dd14e05051896aaecd3b16b53d95 upstream.

Telit 3G Intel based modems require zero packet to be sent if
out data size is equal to the endpoint max packet size.

Signed-off-by: Daniele Palmas &lt;dnlplm@gmail.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>cdc-acm: fix abnormal DATA RX issue for Mediatek Preloader.</title>
<updated>2019-01-09T15:16:44+00:00</updated>
<author>
<name>Macpaul Lin</name>
<email>macpaul.lin@mediatek.com</email>
</author>
<published>2018-12-19T04:11:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=252098084eaccaa6f23959755c273c6b94c633ac'/>
<id>252098084eaccaa6f23959755c273c6b94c633ac</id>
<content type='text'>
commit eafb27fa5283599ce6c5492ea18cf636a28222bb upstream.

Mediatek Preloader is a proprietary embedded boot loader for loading
Little Kernel and Linux into device DRAM.

This boot loader also handle firmware update. Mediatek Preloader will be
enumerated as a virtual COM port when the device is connected to Windows
or Linux OS via CDC-ACM class driver. When the USB enumeration has been
done, Mediatek Preloader will send out handshake command "READY" to PC
actively instead of waiting command from the download tool.

Since Linux 4.12, the commit "tty: reset termios state on device
registration" (93857edd9829e144acb6c7e72d593f6e01aead66) causes Mediatek
Preloader receiving some abnoraml command like "READYXX" as it sent.
This will be recognized as an incorrect response. The behavior change
also causes the download handshake fail. This change only affects
subsequent connects if the reconnected device happens to get the same minor
number.

By disabling the ECHO termios flag could avoid this problem. However, it
cannot be done by user space configuration when download tool open
/dev/ttyACM0. This is because the device running Mediatek Preloader will
send handshake command "READY" immediately once the CDC-ACM driver is
ready.

This patch wants to fix above problem by introducing "DISABLE_ECHO"
property in driver_info. When Mediatek Preloader is connected, the
CDC-ACM driver could disable ECHO flag in termios to avoid the problem.

Signed-off-by: Macpaul Lin &lt;macpaul.lin@mediatek.com&gt;
Cc: stable@vger.kernel.org
Reviewed-by: Johan Hovold &lt;johan@kernel.org&gt;
Acked-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit eafb27fa5283599ce6c5492ea18cf636a28222bb upstream.

Mediatek Preloader is a proprietary embedded boot loader for loading
Little Kernel and Linux into device DRAM.

This boot loader also handle firmware update. Mediatek Preloader will be
enumerated as a virtual COM port when the device is connected to Windows
or Linux OS via CDC-ACM class driver. When the USB enumeration has been
done, Mediatek Preloader will send out handshake command "READY" to PC
actively instead of waiting command from the download tool.

Since Linux 4.12, the commit "tty: reset termios state on device
registration" (93857edd9829e144acb6c7e72d593f6e01aead66) causes Mediatek
Preloader receiving some abnoraml command like "READYXX" as it sent.
This will be recognized as an incorrect response. The behavior change
also causes the download handshake fail. This change only affects
subsequent connects if the reconnected device happens to get the same minor
number.

By disabling the ECHO termios flag could avoid this problem. However, it
cannot be done by user space configuration when download tool open
/dev/ttyACM0. This is because the device running Mediatek Preloader will
send handshake command "READY" immediately once the CDC-ACM driver is
ready.

This patch wants to fix above problem by introducing "DISABLE_ECHO"
property in driver_info. When Mediatek Preloader is connected, the
CDC-ACM driver could disable ECHO flag in termios to avoid the problem.

Signed-off-by: Macpaul Lin &lt;macpaul.lin@mediatek.com&gt;
Cc: stable@vger.kernel.org
Reviewed-by: Johan Hovold &lt;johan@kernel.org&gt;
Acked-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>usb: cdc-acm: add entry for Hiro (Conexant) modem</title>
<updated>2018-11-27T15:09:41+00:00</updated>
<author>
<name>Maarten Jacobs</name>
<email>maarten256@outlook.com</email>
</author>
<published>2018-11-19T23:18:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=9f08cfeb966c15ff6b8938cc027c62ddeb65e6a6'/>
<id>9f08cfeb966c15ff6b8938cc027c62ddeb65e6a6</id>
<content type='text'>
commit 63529eaa6164ef7ab4b907b25ac3648177e5e78f upstream.

The cdc-acm kernel module currently does not support the Hiro (Conexant)
H05228 USB modem. The patch below adds the device specific information:
	idVendor	0x0572
	idProduct	0x1349

Signed-off-by: Maarten Jacobs &lt;maarten256@outlook.com&gt;
Acked-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 63529eaa6164ef7ab4b907b25ac3648177e5e78f upstream.

The cdc-acm kernel module currently does not support the Hiro (Conexant)
H05228 USB modem. The patch below adds the device specific information:
	idVendor	0x0572
	idProduct	0x1349

Signed-off-by: Maarten Jacobs &lt;maarten256@outlook.com&gt;
Acked-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>cdc-acm: correct counting of UART states in serial state notification</title>
<updated>2018-11-10T15:43:00+00:00</updated>
<author>
<name>Tobias Herzog</name>
<email>t-herzog@gmx.de</email>
</author>
<published>2018-09-22T20:11:11+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=25c1b59c21dddc85d15c9e8610547f8f6816ade9'/>
<id>25c1b59c21dddc85d15c9e8610547f8f6816ade9</id>
<content type='text'>
commit f976d0e5747ca65ccd0fb2a4118b193d70aa1836 upstream.

The usb standard ("Universal Serial Bus Class Definitions for Communication
Devices") distiguishes between "consistent signals" (DSR, DCD), and
"irregular signals" (break, ring, parity error, framing error, overrun).
The bits of "irregular signals" are set, if this error/event occurred on
the device side and are immeadeatly unset, if the serial state notification
was sent.
Like other drivers of real serial ports do, just the occurence of those
events should be counted in serial_icounter_struct (but no 1-&gt;0
transitions).

Signed-off-by: Tobias Herzog &lt;t-herzog@gmx.de&gt;
Acked-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit f976d0e5747ca65ccd0fb2a4118b193d70aa1836 upstream.

The usb standard ("Universal Serial Bus Class Definitions for Communication
Devices") distiguishes between "consistent signals" (DSR, DCD), and
"irregular signals" (break, ring, parity error, framing error, overrun).
The bits of "irregular signals" are set, if this error/event occurred on
the device side and are immeadeatly unset, if the serial state notification
was sent.
Like other drivers of real serial ports do, just the occurence of those
events should be counted in serial_icounter_struct (but no 1-&gt;0
transitions).

Signed-off-by: Tobias Herzog &lt;t-herzog@gmx.de&gt;
Acked-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>Revert "usb: cdc-wdm: Fix a sleep-in-atomic-context bug in service_outstanding_interrupt()"</title>
<updated>2018-10-04T00:01:50+00:00</updated>
<author>
<name>Sebastian Andrzej Siewior</name>
<email>bigeasy@linutronix.de</email>
</author>
<published>2018-09-11T08:00:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=5c82d4a60c2f0315a8a550a54a79c80a64101a80'/>
<id>5c82d4a60c2f0315a8a550a54a79c80a64101a80</id>
<content type='text'>
commit e871db8d78df1c411032cbb3acfdf8930509360e upstream.

This reverts commit 6e22e3af7bb3a7b9dc53cb4687659f6e63fca427.

The bug the patch describes to, has been already fixed in commit
2df6948428542 ("USB: cdc-wdm: don't enable interrupts in USB-giveback")
so need to this, revert it.

Fixes: 6e22e3af7bb3 ("usb: cdc-wdm: Fix a sleep-in-atomic-context bug in service_outstanding_interrupt()")
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Sebastian Andrzej Siewior &lt;bigeasy@linutronix.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit e871db8d78df1c411032cbb3acfdf8930509360e upstream.

This reverts commit 6e22e3af7bb3a7b9dc53cb4687659f6e63fca427.

The bug the patch describes to, has been already fixed in commit
2df6948428542 ("USB: cdc-wdm: don't enable interrupts in USB-giveback")
so need to this, revert it.

Fixes: 6e22e3af7bb3 ("usb: cdc-wdm: Fix a sleep-in-atomic-context bug in service_outstanding_interrupt()")
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Sebastian Andrzej Siewior &lt;bigeasy@linutronix.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>Revert "cdc-acm: implement put_char() and flush_chars()"</title>
<updated>2018-09-26T06:36:37+00:00</updated>
<author>
<name>Oliver Neukum</name>
<email>oneukum@suse.com</email>
</author>
<published>2018-09-05T15:56:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=2c8adbfa328384986452fd64e1ad93b24729d418'/>
<id>2c8adbfa328384986452fd64e1ad93b24729d418</id>
<content type='text'>
commit df3aa13c7bbb307e172c37f193f9a7aa058d4739 upstream.

This reverts commit a81cf9799ad7299b03a4dff020d9685f9ac5f3e0.

The patch causes a regression, which I cannot find the reason for.
So let's revert for now, as a revert hurts only performance.

Original report:
I was trying to resolve the problem with Oliver but we don't get any conclusion
for 5 months, so I am now sending this to mail list and cdc_acm authors.

I am using simple request-response protocol to obtain the boiller parameters
in constant intervals.

A simple one transaction is:
1. opening the /dev/ttyACM0
2. sending the following 10-bytes request to the device:
   unsigned char req[] = {0x02, 0xfe, 0x01, 0x05, 0x08, 0x02, 0x01, 0x69, 0xab, 0x03};
3. reading response (frame of 74 bytes length).
4. closing the descriptor
I am doing this transaction with 5 seconds intervals.

Before the bad commit everything was working correctly: I've got a requests and
a responses in a timely manner.

After the bad commit more time I am using the kernel module, more problems I have.
The graph [2] is showing the problem.

As you can see after module load all seems fine but after about 30 minutes I've got
a plenty of EAGAINs when doing read()'s and trying to read back the data.

When I rmmod and insmod the cdc_acm module again, then the situation is starting
over again: running ok shortly after load, and more time it is running, more EAGAINs
I have when calling read().

As a bonus I can see the problem on the device itself:
The device is configured as you can see here on this screen [3].
It has two transmision LEDs: TX and RX. Blink duration is set for 100ms.
This is a recording before the bad commit when all is working fine: [4]
And this is with the bad commit: [5]
As you can see the TX led is blinking wrongly long (indicating transmission?)
and I have problems doing read() calls (EAGAIN).

Reported-by: Mariusz Bialonczyk &lt;manio@skyboo.net&gt;
Signed-off-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Fixes: a81cf9799ad7 ("cdc-acm: implement put_char() and flush_chars()")
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit df3aa13c7bbb307e172c37f193f9a7aa058d4739 upstream.

This reverts commit a81cf9799ad7299b03a4dff020d9685f9ac5f3e0.

The patch causes a regression, which I cannot find the reason for.
So let's revert for now, as a revert hurts only performance.

Original report:
I was trying to resolve the problem with Oliver but we don't get any conclusion
for 5 months, so I am now sending this to mail list and cdc_acm authors.

I am using simple request-response protocol to obtain the boiller parameters
in constant intervals.

A simple one transaction is:
1. opening the /dev/ttyACM0
2. sending the following 10-bytes request to the device:
   unsigned char req[] = {0x02, 0xfe, 0x01, 0x05, 0x08, 0x02, 0x01, 0x69, 0xab, 0x03};
3. reading response (frame of 74 bytes length).
4. closing the descriptor
I am doing this transaction with 5 seconds intervals.

Before the bad commit everything was working correctly: I've got a requests and
a responses in a timely manner.

After the bad commit more time I am using the kernel module, more problems I have.
The graph [2] is showing the problem.

As you can see after module load all seems fine but after about 30 minutes I've got
a plenty of EAGAINs when doing read()'s and trying to read back the data.

When I rmmod and insmod the cdc_acm module again, then the situation is starting
over again: running ok shortly after load, and more time it is running, more EAGAINs
I have when calling read().

As a bonus I can see the problem on the device itself:
The device is configured as you can see here on this screen [3].
It has two transmision LEDs: TX and RX. Blink duration is set for 100ms.
This is a recording before the bad commit when all is working fine: [4]
And this is with the bad commit: [5]
As you can see the TX led is blinking wrongly long (indicating transmission?)
and I have problems doing read() calls (EAGAIN).

Reported-by: Mariusz Bialonczyk &lt;manio@skyboo.net&gt;
Signed-off-by: Oliver Neukum &lt;oneukum@suse.com&gt;
Fixes: a81cf9799ad7 ("cdc-acm: implement put_char() and flush_chars()")
Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
</feed>
