linux-kernel - Re: [PATCH v3 7/7] [SCSI] sr: adds Zero-power ODD support

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Date:	Thu, 5 Apr 2012 16:32:45 +0800
From:	Aaron Lu <aaron.lu@....com>
To:	Lin Ming <ming.m.lin@...el.com>
CC:	Alan Stern <stern@...land.harvard.edu>,
	Zhang Rui <rui.zhang@...el.com>,
	Jeff Garzik <jgarzik@...ox.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Tejun Heo <tj@...nel.org>,
	<linux-kernel@...r.kernel.org>, <linux-ide@...r.kernel.org>,
	<linux-scsi@...r.kernel.org>, <linux-pm@...r.kernel.org>,
	linux-acpi <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v3 7/7] [SCSI] sr: adds Zero-power ODD support

Hi,

On Thu, Apr 05, 2012 at 02:00:57PM +0800, Lin Ming wrote:
> >
> > Another thing to consider is, user might want to eject the tray by
> > software like the
> > eject /dev/sr0 command or some UI mouse clicks against the cdrom icon. I'm still
> > thinking how to do this correctly.
> 
> Assume eject /dev/sr0 is implemented as:
> 
> int fd = open("/dev/sr0", ...)
> ioctl(fd, CDROMEJECT)
> 

Indeed, it is implemented as this :-)

> We may need to resume ODD in the ioctl handler(scsi_cmd_ioctl).
> 

I prefer we do this in sr_block_ioctl.
Suppose the ODD is now runtime suspended and received an ioctl:
if the ioctl's cmd is CDROMEJECT, resume it.
For other cases, return an error code like EPERM.
When done, according to the result of ioctl: if success, leave it resumed;
if failed, put it back to sleep.

Something like this:

diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 5fc97d2..aa6e920 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -45,6 +45,7 @@
 #include <linux/blkdev.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/pm_runtime.h>
 #include <asm/uaccess.h>
 
 #include <scsi/scsi.h>
@@ -538,10 +539,21 @@ static int sr_block_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
        struct scsi_cd *cd = scsi_cd(bdev->bd_disk);
        struct scsi_device *sdev = cd->device;
        void __user *argp = (void __user *)arg;
-       int ret;
+       int ret, rpm_resumed = 0;
 
        mutex_lock(&sr_mutex);
 
+       if (pm_runtime_suspended(&sdev->sdev_gendev)) {
+               if (cmd == CDROMEJECT) {
+                       scsi_autopm_get_device(sdev);
+                       rpm_resumed = 1;
+               }
+               else {
+                       ret = -EPERM;
+                       goto out;
+               }
+       }
+
        /*
         * Send SCSI addressing ioctls directly to mid level, send other
         * ioctls to cdrom/block level.
@@ -570,6 +582,9 @@ static int sr_block_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
        ret = scsi_ioctl(sdev, cmd, argp);
 
 out:
+       if (rpm_resumed && ret)
+               scsi_autopm_put_device(sdev);
+
        mutex_unlock(&sr_mutex);
        return ret;
 }

Does this work?

-Aaron


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