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

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Message-ID: <CAF1ivSYofajj+hr8zDGA=1c0J5mTjdqojjvyE5x1C3g1MkhgYA@mail.gmail.com>
Date:	Thu, 5 Apr 2012 16:48:06 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Aaron Lu <aaron.lu@....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

On Thu, Apr 5, 2012 at 4:32 PM, Aaron Lu <aaron.lu@....com> wrote:
> 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.

That's better.

> 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?

I think so.
Will add this patch.

Thanks,
Lin Ming

>
> -Aaron
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