[PATCH V3 0/3] cdc-acm: fix incorrect runtime wakeup in acm_tty_write

[Zhang, Yanmin]

Resend as V1/V2 have email format issue. Sorry for bothering.

I use Thunderbird. It has no a button to enable LKML email simply. :)

V3: Change email config to resend.
	Add a space in comment.

 ---

There is a scenario about cdc-acm utilization.Application opens
n_gsm tty and cdc-acm tty. cdc-acm tty connects to xhci device.
The application configures cdc-adm tty to n_gsm tty as ldisc tty.

    n_gsm=>cdc-acm=>xhci driver

acm_tty_write can be called from n_gsm driver by ldisc connection,
and from application when application opens cdc-acm tty directly.
acm_tty_write wakes up the device by calling usb_autopm_get_interface_async,
which calls pm_runtime_get. However, pm_runtime_get can't wake up
the device before returning as it's an async wake up. Then, acm_tty_write
might access the device when it is off.

The patchset fixes it by:
1) add a new function usb_autopm_get_interface_upgrade to deal with
above 2 requirements;
2) wake up device in n_gsm driver if n_gsm drivers calls cdc-acm driver;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/