[010/200] libata: disable ATAPI AN by default

[Greg KH]

2.6.34-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tejun Heo <tj@xxxxxxxxxx>

commit e7ecd435692ca9bde9d124be30b3a26e672ea6c2 upstream.

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@xxxxxxxxxx>
Cc: Kay Sievers <kay.sievers@xxxxxxxx>
Cc: Nick Bowler <nbowler@xxxxxxxxxxxxxxxx>
Cc: David Zeuthen <david@xxxxxxxx>
Signed-off-by: Jeff Garzik <jgarzik@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/ata/libata-core.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- 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");
@@ -2572,7 +2576,8 @@ int ata_dev_configure(struct ata_device
 		 * 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;


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