Messages in this thread | | | Subject | Re: [PATCH] usb/serial: Add compat_ioctl pass-through | From | Keith Packard <> | Date | Thu, 27 Nov 2008 10:27:04 -0800 |
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On Thu, 2008-11-27 at 15:31 +0100, Arnd Bergmann wrote: > On Thursday 27 November 2008, Keith Packard wrote: > > +static long serial_compat_ioctl(struct tty_struct *tty, struct file *file, > > + unsigned int cmd, unsigned long arg) > > +{ > > + struct usb_serial_port *port = tty->driver_data; > > + long retval = -ENODEV; > > + > > + dbg("%s - port %d, cmd 0x%.4x", __func__, port->number, cmd); > > + > > + WARN_ON(!port->port.count); > > + > > + /* pass on to the driver specific version of this function > > + if it is available */ > > + if (port->serial->type->compat_ioctl) { > > + lock_kernel(); > > + retval = port->serial->type->compat_ioctl(tty, file, cmd, arg); > > + unlock_kernel(); > > By convention, compat_ioctl functions should be called without the big kernel > lock held.
Thanks - I didn't realize these were supposed to be different.
> You should probably define compat_ioctl to return an int as well > so that it becomes possible to use the same function for both eventually.
The existing tty layer compat_ioctl is defined to return long; is that also wrong?
> Then again, we can also drop the file argument, which is entirely unused > in all the usb-serial ioctls.
I'm not sure it's worth the effort; if some future usb serial ioctl needs the argument, we'd end up changing every existing driver back. I assume there are some serial devices for which the file is relevant during ioctl.
> Maybe the best way for now is to make the new compat_ioctl be > int compat_ioctl(struct tty_struct, unsigned int cmd, unsigned long arg); > and leave the old ioctl as it is. When we get around to pushing the > BKL down into ->ioctl, we can change the prototype at the same time > to warn potential out-of-tree drivers.
Let's figure out what the right compat_ioctl interface is first and worry about fixing the existing ioctl interface later.
-- keith.packard@intel.com [unhandled content-type:application/pgp-signature] | |