linux-kernel - Re: [RFC PATCH v2 8/8] [SCSI] sr: check and enable Zero-power ODD support

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Date:	Fri, 02 Mar 2012 15:02:45 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Zhang Rui <rui.zhang@...el.com>, Jeff Garzik <jgarzik@...ox.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Tejun Heo <tj@...nel.org>,
	Aaron Lu <aaron.lu@....com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	linux-ide@...r.kernel.org,
	SCSI development list <linux-scsi@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...r.kernel.org>,
	linux-acpi <linux-acpi@...r.kernel.org>
Subject: Re: [RFC PATCH v2 8/8] [SCSI] sr: check and enable Zero-power ODD
 support

On Thu, 2012-03-01 at 11:02 -0500, Alan Stern wrote:
> On Thu, 1 Mar 2012, Lin Ming wrote:
> 
> > ZPODD(Zero Power Optical Disk Drive) is a new feature in
> > SATA 3.1 specification. It provides a way to power off unused ODD.
> > 
> > ZPODD support is checked in in sr_probe().
> > can_power_off flag is set during suspend if ZPODD is supported.
> > 
> > ATA port's runtime suspend callback will actually power off the ODD
> > and its runtime resume callback will actually power on the ODD.
> > 
> > When ODD is powered off(D3Cold state), inserting disk will trigger a
> > wakeup event(GPE). GPE AML handler notifies the associated device. Then
> > ODD is resumed in the notify handler.
> 
> I have one stylistic comment on this patch...
> 
> > diff --git a/drivers/scsi/sr.h b/drivers/scsi/sr.h
> > index 37c8f6b..39b3d8c 100644
> > --- a/drivers/scsi/sr.h
> > +++ b/drivers/scsi/sr.h
> > @@ -42,6 +42,9 @@ typedef struct scsi_cd {
> >  	unsigned readcd_cdda:1;	/* reading audio data using READ_CD */
> >  	unsigned media_present:1;	/* media is present */
> >  
> > +	unsigned zpodd:1;	/* is ZPODD supported */
> > +	unsigned zpodd_event:1;
> > +
> 
> You should not expect your readers to understand what "ZPODD" means.  
> drivers/scsi/sr.h is used by lots of different people, many of whom 
> will have no idea what it refers to, especially since it is part of 
> the SATA spec and not the SCSI spec.  You should provide a brief 
> explanation.

I'll add some explanation.

But I'm thinking maybe it's better to move this flag to ata layer, for
example, adding a flag to libata.h

ATA_DFLAG_ZPODD

sr runtime pm is only enabled when ZPODD(or more general, power off) is
supported.
So the problem is how will sr driver know this flag?


> 
> Alan Stern
> 


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