Patchwork [v6,5/7] scsi: pm: add may_power_off flag

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Submitter Aaron Lu
Date Sept. 4, 2012, 2:24 p.m.
Message ID <1346768680-7287-6-git-send-email-aaron.lwe@gmail.com>
Download mbox | patch
Permalink /patch/181588/
State Not Applicable
Delegated to: David Miller
Headers show

Comments

Aaron Lu - Sept. 4, 2012, 2:24 p.m.
From: Aaron Lu <aaron.lu@intel.com>

Add a new flag may_power_off for scsi device, it gives the user a chance
to control when the device is runtime suspended, can we remove its power
if possible.

And if the device can be powered off(reflected by can_power_off flag,
determined by individual driver), create a sysfs entry named
may_power_off to let user control the flag.

When user changes this flag through sysfs entry and if the device is
already runtime suspended, runtime resume it so that it can respect this
flag next time it is runtime suspended.

I'm planning using this flag for sr and sd.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
---
 drivers/scsi/scsi_sysfs.c  | 37 ++++++++++++++++++++++++++++++++++++-
 include/scsi/scsi_device.h |  1 +
 2 files changed, 37 insertions(+), 1 deletion(-)
Oliver Neukum - Sept. 4, 2012, 4:01 p.m.
On Tuesday 04 September 2012 22:24:38 Aaron Lu wrote:
> From: Aaron Lu <aaron.lu@intel.com>
> 
> Add a new flag may_power_off for scsi device, it gives the user a chance
> to control when the device is runtime suspended, can we remove its power
> if possible.
> 
> And if the device can be powered off(reflected by can_power_off flag,
> determined by individual driver), create a sysfs entry named
> may_power_off to let user control the flag.

Do we really need yet another interface to user space?

	Regards
		Oliver

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Aaron Lu - Sept. 6, 2012, 1:52 a.m.
On Tue, Sep 04, 2012 at 06:01:22PM +0200, Oliver Neukum wrote:
> On Tuesday 04 September 2012 22:24:38 Aaron Lu wrote:
> > From: Aaron Lu <aaron.lu@intel.com>
> > 
> > Add a new flag may_power_off for scsi device, it gives the user a chance
> > to control when the device is runtime suspended, can we remove its power
> > if possible.
> > 
> > And if the device can be powered off(reflected by can_power_off flag,
> > determined by individual driver), create a sysfs entry named
> > may_power_off to let user control the flag.
> 
> Do we really need yet another interface to user space?

We do not have a way to let user decide when device is runtime
suspended, can we remove its power, so I added this flag. PCI subsystem
has a similar flag named d3cold_allowed.

This flag can disable the power off of ZPODD capable devices, or put a
rotational disk into powered off if user so choose.

Thanks,
Aaron
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Patch

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 093d4f6..8c8efd3 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -509,6 +509,7 @@  sdev_store_##field (struct device *dev, struct device_attribute *attr,	\
 	return ret;							\
 }									\
 static DEVICE_ATTR(field, S_IRUGO | S_IWUSR, sdev_show_##field, sdev_store_##field);
+#endif
 
 /*
  * scsi_sdev_check_buf_bit: return 0 if buf is "0", return 1 if buf is "1",
@@ -526,7 +527,7 @@  static int scsi_sdev_check_buf_bit(const char *buf)
 	} else
 		return -EINVAL;
 }
-#endif
+
 /*
  * Create the actual show/store functions and data structures.
  */
@@ -860,6 +861,37 @@  static struct device_attribute sdev_attr_queue_type_rw =
 	__ATTR(queue_type, S_IRUGO | S_IWUSR, show_queue_type_field,
 	       sdev_store_queue_type_rw);
 
+static ssize_t
+sdev_show_may_power_off(struct device *dev, struct device_attribute *attr,
+			char *buf)
+{
+	struct scsi_device *sdev;
+	sdev = to_scsi_device(dev);
+	return snprintf (buf, 20, "%d\n", sdev->may_power_off);
+}
+
+static ssize_t
+sdev_store_may_power_off(struct device *dev, struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	int ret;
+	struct scsi_device *sdev;
+
+	ret = scsi_sdev_check_buf_bit(buf);
+	if (ret >= 0) {
+		sdev = to_scsi_device(dev);
+		if (sdev->may_power_off != ret) {
+			sdev->may_power_off = ret;
+			if (pm_runtime_suspended(dev))
+				pm_runtime_resume(dev);
+		}
+		ret = count;
+	}
+	return ret;
+}
+static DEVICE_ATTR(may_power_off, S_IRUGO | S_IWUSR,
+			sdev_show_may_power_off, sdev_store_may_power_off);
+
 /**
  * scsi_sysfs_add_sdev - add scsi device to sysfs
  * @sdev:	scsi_device to add
@@ -950,6 +982,9 @@  int scsi_sysfs_add_sdev(struct scsi_device *sdev)
 		}
 	}
 
+	if (sdev->can_power_off)
+		device_create_file(&sdev->sdev_gendev, &dev_attr_may_power_off);
+
 	return error;
 }
 
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 72d946f..41cec7f 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -157,6 +157,7 @@  struct scsi_device {
 	unsigned can_power_off:1; /* Device supports runtime power off */
 	unsigned wce_default_on:1;	/* Cache is ON by default */
 	unsigned wakeup_by_user:1;	/* User wakes up the device */
+	unsigned may_power_off:1;	/* Power off is allowed by user */
 
 	DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
 	struct list_head event_list;	/* asserted events */