linux-kernel - [PATCH] scsi: scsi_sysfs.c: Hide wwid sdev attr if VPD is not supported

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Message-Id: <20190612020828.8140-1-marcos.souza.org@gmail.com>
Date:   Tue, 11 Jun 2019 23:08:28 -0300
From:   Marcos Paulo de Souza <marcos.souza.org@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Marcos Paulo de Souza <marcos.souza.org@...il.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org (open list:SCSI SUBSYSTEM)
Subject: [PATCH] scsi: scsi_sysfs.c: Hide wwid sdev attr if VPD is not supported

WWID composed from VPD data from device, specifically page 0x83. So,
when a device does not have VPD support, for example USB storage devices
where VPD is specifically disabled, a read into <blk device>/device/wwid
file will always return ENXIO. To avoid this, change the
scsi_sdev_attr_is_visible function to hide wwid sysfs file when the
devices does not support VPD.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@...il.com>
---
 drivers/scsi/scsi_sysfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index dbb206c90ecf..bfd890fa0c69 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1159,6 +1159,9 @@ static umode_t scsi_sdev_attr_is_visible(struct kobject *kobj,
 	struct device *dev = container_of(kobj, struct device, kobj);
 	struct scsi_device *sdev = to_scsi_device(dev);
 
+	/* do not present wwid if the device does not support VPD */
+	if (attr == &dev_attr_wwid.attr && sdev->skip_vpd_pages)
+		return 0;
 
 	if (attr == &dev_attr_queue_depth.attr &&
 	    !sdev->host->hostt->change_queue_depth)
-- 
2.21.0