On Tue, Jan 09, 2007 at 09:37:21PM +0100, Hans Petter Selasky wrote:
> On Tuesday 09 January 2007 17:34, Luigi Rizzo wrote:
> > [sorry for the repost, not sure it went through]
> >
> > On Tue, Jan 09, 2007 at 08:16:29AM -0800, Luigi Rizzo wrote:
> > I am modifying a kernel device driver for webcams
> > (see http://info.iet.unipi.it/~luigi/FreeBSD/usb-cameras.html)
> > packing together various projects around, and i was wondering
> > how to handle the situation of a device being
> > detached while in use.
>
> If you look at the my USB driver for FreeBSD,
> http://www.turbocat.net/~hselasky/usb4bsd , there has been created a new
> device system, usb_cdev, with that goal in mind that you should not have to
> worry about detaching devices, hence this is somewhat complicated:
>
> http://www.turbocat.net/~hselasky/isdn4bsd/sources/src/sys/dev/usb/usb_cdev.c
>
> For example, have a look a the new URIO driver:
>
> http://www.turbocat.net/~hselasky/isdn4bsd/sources/src/sys/dev/usb/urio.c
sorry but i cannot figure out how the above helps in the
detach case e.g. when a process is waiting for an ioctl
or read operation to complete - can you give more details ?
In my case, i did the following:
USB_DETACH(pwc)
{
USB_DETACH_START(pwc, sc);
again:
if(sc->sc_videopipe != NULL) {
usbd_abort_pipe(sc->sc_videopipe);
usbd_close_pipe(sc->sc_videopipe);
sc->sc_videopipe = NULL;
}
sc->error_status = EPIPE;
if(sc->vopen) {
if(sc->state & PWC_ASLEEP)
wakeup(sc);
if(sc->state & PWC_POLL) {
sc->state &= ~PWC_POLL;
selwakeuppri(&sc->rsel,PZERO);
}
device_printf(sc->sc_dev, "Disconnected while webcam is in
use!\n");
usb_detach_wait(USBDEV(sc->sc_dev));
goto again;
}
if(sc->sc_dev_t != NULL)
destroy_dev(sc->sc_dev_t);
mtx_destroy(&sc->ptrlock);
pwc_free_buffers(sc,1);
usbd_add_drv_event(USB_EVENT_DRIVER_DETACH,sc->udev,USBDEV(sc->sc_dev));
return 0;
}
and at the end of the close routine
...
sc->vopen = 0;
usb_detach_wakeup(USBDEV(sc->sc_dev));
}
so the USB_DETACH() will wake up any process blocked,
the sc->error_status = EPIPE; should force an error and
cause the process to call close().
The down side is that you are still in the hands
of the process to let the detach complete. Ideally one
would just flag the descriptor as 'detach_pending'
and get rid of it at the end of the close(), while the
DETACH() could terminate without doing the free()
cheers
luigi
> >
> > Right now the code (from ports/multimedia/pwcbsd) detects
> > that the device is in use while the driver-specific USB_DETACH
> > routine is called, however then it goes on without doing
> > anything.
>
> Very bad!
>
> >
> > In another driver in the dree (urio.c) i see the driver
> > calls usb_detach_wait() to wait up to 60s for the
> > drivers to complete. However that function is not documented
> > and used a bit inconsistently in the rest of /sys/dev/usb
> >
>
> --HPS
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