Date: Wed, 7 Jan 2004 12:05:16 +0100
From: Jens Axboe <axboe@suse.de>
To: Andrey Borzenkov <arvidjaar@mail.ru>
Cc: Olaf Hering <olh@suse.de>, Andries Brouwer <aebr@win.tue.nl>,
       Greg KH <greg@kroah.com>, linux-hotplug-devel@lists.sourceforge.net,
       linux-kernel@vger.kernel.org
Subject: Re: removable media revalidation - udev vs. devfs or static /dev
Message-ID: <20040107110516.GC3483@suse.de>
References: <200401012333.04930.arvidjaar@mail.ru> <20040107094321.GC21059@suse.de> <20040107095029.GX3483@suse.de> <200401071400.46286.arvidjaar@mail.ru>
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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.

-- 
Jens Axboe

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