Tom Zoerner <tomzo@xxxxxxxxxx> writes:
> Hi Gerd & list members,
>
> Gerd Knorr wrote:
> > I agree that priority levels are likely to complex.
>
> I was just trying to look ahead a little and find a solution that does
> not only solve my immediate problem. I do se a very similar problem
> one level up: when the user forgets that he has a TV recording running,
> he might fire up his TV app and start zapping through the channels,
> thereby destroying the recording. Of course that would be the user's
> fault, but it would be nice if there would be a way to prevent that
> kind of error in the first place.
Software trying to be more clever than the user is IMHO a bad idea ...
> > Another way would be to have some kind of O_EXCL flag, but at ioctl
> > level. So nxtvepg could set that for the S_FREQUENCY ioctl and the
> > driver would refuse the switch with -EBUSY if there is more than one
> > file handle open at that time.
>
> This would solve my problem, but not the one described above.
>
> Also, wouldn't that mean to add a flag to every struct that's passed
> to a "set" type ioctl?
Yes.
> To me (certainly not a driver expert) it'd seem simpler to pass this
> value once in a dedicated ioctl and keep it in the driver.
That would do the job equally well, yes.
> If you agree to that, you could also take the next step and make an
> integer out of the boolean flag and do a loop across all device
> users to find the maximum value, before doing the EBUSY refusal.
That isn't a small step. bttv doesn't even has a list of all device
users.
I think with open(O_EXCL) it would work if you close the device before
attempting to switch the tv station, i.e. like this:
open(/dev/vbi,0)
[ read vbi data ]
close(/dev/vbi)
if (open(/dev/vbi,O_EXCL)) {
[ switch station ]
close(/dev/vbi)
}
open(/dev/vbi,0)
[ read more vbi data ]
close(/dev/vbi)
Comments?
Gerd
--
Weil die späten Diskussionen nicht mal mehr den Rotwein lohnen.
-- Wacholder in "Melanie"
