GIT: unionfs2-2.6.27.y: libata: disable ATAPI AN by default

[Erez Zadok]

commit 90bfd720bcda3a04e22be93b66138a117c0bcf28
Author: Tejun Heo <tj at kernel.org>
Date:   Wed May 19 15:38:58 2010 +0200

    libata: disable ATAPI AN by default
    
    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 at kernel.org>
    Cc: Kay Sievers <kay.sievers at vrfy.org>
    Cc: Nick Bowler <nbowler at elliptictech.com>
    Cc: David Zeuthen <david at fubar.dk>
    Signed-off-by: Jeff Garzik <jgarzik at redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 8afc274..512c281 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -157,6 +157,10 @@ 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");
 
+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");
@@ -2341,7 +2345,8 @@ 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;