Re: removable media revalidation - udev vs. devfs or static /dev

Jens Axboe
2004-01-07T11:16:12Z

On Wed, Jan 07 2004, Andrey Borzenkov wrote:
> On Wednesday 07 January 2004 14:05, Jens Axboe wrote:
> > On Wed, Jan 07 2004, Andrey Borzenkov wrote:
> > > On Wednesday 07 January 2004 12:50, Jens Axboe wrote:
> > > > > > So yeah, poll...
> > > > >
> > > > > Poll how? "kmediachangethread"? Or polling in userland? The latter
> > > > > would (probably) lead to endless IO errors. Not very good.
> > > >
> > > > No need to put it in the kernel, user space fits the bil nicely.
> > >
> > > unfortunately opening device in userland effectively locks tray making
> > > media change impossible. at least given current ->open semantic.
> > >
> > > even periodic access is quite annoying for users (tray closing while
> > > user attempts to insert CD)
> >
> > cdrom layer handles this with O_NONBLOCK basically meaning a 'not for
> > data' open.
> >
> > > we may agree that O_NDELAY does not affect locked state; currently
> > > this is not consistent across drivers (e.g. cdrom does not lock tray
> > > while sd does)
> >
> > cdrom has no special O_NDELAY checks.
>
> ok I meant O_NONBLOCK, sorry. they are synonyms anyway
>
> {pts/0}% grep NONBLO *
> fcntl.h:#define O_NONBLOCK 04000
> fcntl.h:#define O_NDELAY O_NONBLOCK

Oh right, so same thing :-). cdrom layer has always documented it as
O_NONBLOCK.

--
Jens Axboe