[PATCH v3 3/3] scsi: add shost attribute to set max queue depth on all devices on the shost

[James Smart <jsmart2021@gmail.com>]

This patch adds an shost attribute, max_device_queue_depth, that will
cycle through all devices on the shost and change their current and max
queue depth to the new value.

Signed-off-by: James Smart <jsmart2021@gmail.com>

---
v3:
 use kstrtouint
 specify permissions in octl, not by mnemonic
 remove unnecessary parens
---
 drivers/scsi/scsi_sysfs.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index d4e9ad9a6f18..98dbbfb6397b 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -368,6 +368,26 @@ store_shost_eh_deadline(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR(eh_deadline, S_IRUGO | S_IWUSR, show_shost_eh_deadline, store_shost_eh_deadline);
 
+static ssize_t
+store_host_max_device_queue_depth(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	unsigned int depth;
+	int retval;
+
+	retval = kstrtouint(buf, 10, &depth);
+	if (retval)
+		return -EINVAL;
+
+	retval = shost_change_max_queue_depths(shost, depth);
+
+	return retval < 0 ? retval : count;
+}
+
+static DEVICE_ATTR(max_device_queue_depth, 0200, NULL,
+		   store_host_max_device_queue_depth);
+
 shost_rd_attr(unique_id, "%u\n");
 shost_rd_attr(cmd_per_lun, "%hd\n");
 shost_rd_attr(can_queue, "%hd\n");
@@ -411,6 +431,7 @@ static struct attribute *scsi_sysfs_shost_attrs[] = {
 	&dev_attr_prot_guard_type.attr,
 	&dev_attr_host_reset.attr,
 	&dev_attr_eh_deadline.attr,
+	&dev_attr_max_device_queue_depth.attr,
 	NULL
 };
 
-- 
2.13.7