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>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index c47373f01f89..8959f42c5b3b 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -160,6 +160,10 @@ int libata_allow_tpm = 0;
 module_param_named(allow_tpm, libata_allow_tpm, int, 0444);
 MODULE_PARM_DESC(allow_tpm, "Permit the use of TPM commands (0=off [default], 1=on)");
 
+static int atapi_an;
+module_param(atapi_an, int, 0444);
+MODULE_PARM_DESC(atapi_an, "Enable ATAPI AN media presence notification (0=0ff [default], 1=on)");
+
 MODULE_AUTHOR("Jeff Garzik");
 MODULE_DESCRIPTION("Library module for ATA devices");
 MODULE_LICENSE("GPL");
@@ -2510,7 +2514,8 @@ int ata_dev_configure(struct ata_device *dev)
                  * to enable ATAPI AN to discern between PHY status
                  * changed notifications and ATAPI ANs.
                  */
-                if ((ap->flags & ATA_FLAG_AN) && ata_id_has_atapi_AN(id) &&
+                if (atapi_an &&
+                    (ap->flags & ATA_FLAG_AN) && ata_id_has_atapi_AN(id) &&
                     (!sata_pmp_attached(ap) ||
                      sata_scr_read(&ap->link, SCR_NOTIFICATION, &sntf) == 0)) {
                         unsigned int err_mask;