Re: udev cdrom_id rules prevent unmounted CD from spinning down

[Tejun Heo <tj@kernel.org>]

Hello,

On 05/18/2010 07:53 PM, Kay Sievers wrote:
> Tejun,
> an AN capable SATA optical drive seems to send AN events with every
> open(). For userspace these look the same as the media changed events,
> and cause a loop when udev checks if there is a new media. Any ideas
> if these AN events are expected, or useful for anything?

The open() path issues several commands and it could be that the drive
is raising AN when certain conditions are met just in case.  After all
windows only uses single command for media presence polling, so
there's nothing stopping vendors from using TUR, for example, as the
level triggered check point to see whether media is available and
raise AN if so.  After all, that wouldn't lose any event and in case
the internal state went out of sync, it would work as an easy resync
point.

Long term, I think the only solution is to do what windows does for
media presence polling; otherwise, we'll keep running into various
obscure issues.  For short term, I dunno.  Don't use AN for the time
being?  :-)

Thanks.

-- 
tejun