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

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