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833415a3e7
The driver enforces a strict one-to-one relationship between the received RESPONSE_AVAILABLE notifications and messages read from the device. At the same time, it will cancel the interrupt URB when there is no client holding the character device open. Many devices do not cope well with this behaviour. They maintain a FIFO queue of messages, and send notifications on a best effort basis. Messages are queued regardless of whether the notification is successful or not. So if the driver loses a single notification, which can easily happen when the interrupt URB is cancelled, then the device and driver becomes out-of-sync. New messages end up at the end of the queue, while the associated notification makes the driver read only the first message from the queue. This state is permanent from a user point of view. There is no no way to flush the device queue without resetting the device or using another driver. The problem is easy to hit with current QMI and MBIM command line tools, which typically close the character device after seeing the reply they expect. Any pending unsolicited messages from the device will then trigger the driver bug. Fix by always reading all queued messages from the device when the notification URB is first submitted. This is expected to end with an -EPIPE status when there are no more pending messages, so demote the printk associated with -EPIPE to debug level. The workaround has been tested on a large number of different MBIM and QMI devices, as well as the Ericsson F5521gw and H5321gw modems with real Device Management functions. Signed-off-by: Bjørn Mork <bjorn@mork.no> Acked-by: Oliver Neukum <oneukum@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| cdc-acm.c | ||
| cdc-acm.h | ||
| cdc-wdm.c | ||
| Kconfig | ||
| Makefile | ||
| usblp.c | ||
| usbtmc.c | ||