Hi Tejun,

On 12/04/2012 12:23 AM, Tejun Heo wrote:

Hello, James.

On Mon, Dec 03, 2012 at 08:25:43AM +0000, James Bottomley wrote:

quoted

quoted

diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index e65c62e..1756151 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h

@@ -160,6 +160,7 @@ struct scsi_device {
 	unsigned can_power_off:1; /* Device supports runtime power off */
 	unsigned wce_default_on:1;	/* Cache is ON by default */
 	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
+	unsigned event_driven:1; /* No need to poll the device */
 
 	DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
 	struct list_head event_list;	/* asserted events */

Yes, but if we can get away with doing that, it should be in genhd
because it's completely generic.

I was imagining we'd have to fake the reply to the test unit ready or
some other commands, which is why it would need to be in sr.c

The check events code is Tejun's baby, if he's OK with it then just do
it in genhd.c

The problem here is there's no easy to reach genhd from libata (or the
other way around) without going through sr.  I think we're gonna have
to have something in sr one way or the other.

Do you think we can do something like the following to get the gendisk
pointer in libata? - We have ata_dev->sdev->sdev_gendev, and the
gendisk->part0.__dev is a child of it, so we can loop scan sdev_gendev's
children to see which one is of block_class and disk_type. Assuming one
device will alloc only one disk(correct?), we can get the gendisk from
libata layer. Code like this:

diff --git a/block/genhd.c b/block/genhd.c
index 9a289d7..448b201 100644
--- a/block/genhd.c
+++ b/block/genhd.c

@@ -1619,6 +1619,38 @@ static void disk_events_workfn(struct work_struct *work)
 		kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
 }
 
+static int is_gendisk_part0(struct device *dev, void *data)
+{
+	struct device **child = data;
+
+	if (dev->class == &block_class && dev->type == &disk_type) {
+		*child = dev;
+		return 1;
+	} else
+		return 0;
+}
+
+/**
+ * disk_from_device - Get the gendisk pointer for this device.
+ * @dev: the device this gendisk is created for, i.e. gendisk->driverfs_dev
+ *
+ * LLD sometimes need to play with the gendisk without HLD's aware,
+ * this routine gives LLD the required access to gendisk.
+ *
+ * CONTEXT:
+ * Don't care.
+ */
+struct gendisk *disk_from_device(struct device *dev)
+{
+	struct device *child;
+
+	if (device_for_each_child(dev, &child, is_gendisk_part0))
+		return dev_to_disk(child);
+	else
+		return NULL;
+}
+EXPORT_SYMBOL(disk_from_device);
+
 /*
  * A disk events enabled device has the following sysfs nodes under
  * its /sys/block/X/ directory.

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 79b8bba..e8002c0 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h

@@ -427,6 +427,7 @@ extern void disk_block_events(struct gendisk *disk);
 extern void disk_unblock_events(struct gendisk *disk);
 extern void disk_flush_events(struct gendisk *disk, unsigned int mask);
 extern unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask);
+extern struct gendisk *disk_from_device(struct device *dev);
 
 /* drivers/char/random.c */
 extern void add_disk_randomness(struct gendisk *disk);

Then together with disk_try_block_events and disk_unblock_events, we can
avoid touching SCSI layer to let ODD stay in zero power state.

So what do you think?

Thanks,
Aaron