libata: disable ATAPI AN by default

libata: disable ATAPI AN by default

There are ATAPI devices which raise AN when hit by commands issued by
open().  This leads to infinite loop of AN -> MEDIA_CHANGE uevent ->
udev open() to check media -> AN.

Both ACS and SerialATA standards don't define in which case ATAPI
devices are supposed to raise or not raise AN.  They both list media
insertion event as a possible use case for ATAPI ANs but there is no
clear description of what constitutes such events.  As such, it seems
a bit too naive to export ANs directly to userland as MEDIA_CHANGE
events without further verification (which should behave similarly to
windows as it apparently is the only thing that some hardware vendors
are testing against).

This patch adds libata.atapi_an module parameter and disables ATAPI AN
by default for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Nick Bowler <nbowler@elliptictech.com>
Cc: David Zeuthen <david@fubar.dk>
Cc: stable@kernel.org
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>