Re: [PATCH v7 2/6] scsi: sr: support runtime pm

[Aaron Lu <aaron.lu@intel.com>]

On 09/25/2012 10:23 PM, Oliver Neukum wrote:
> On Tuesday 25 September 2012 22:20:21 Aaron Lu wrote:
>> On Tue, Sep 25, 2012 at 01:47:52PM +0200, Rafael J. Wysocki wrote:
>>> On Tuesday, September 25, 2012, Aaron Lu wrote:
>>>> I'm thinking of enabling this GPE in sr_suspend once we decided that it
>>>> is ready to be powered off, so the time frame between sr_suspend and
>>>> when the power is actually removed in libata should be taken care of by
>>>> the GPE. If GPE fires, the notification function will request a runtime
>>>> resume of the device. Does this sound OK?
>>>
>>> Well, depending on the implementation.  sr_suspend() should be rather
>>> generic, but the ACPI association (including the GPE thing) is specific to ATA.
>>
>> Sorry, but don't quite understand this.
>>
>> We have ACPI bindings for scsi devices, isn't that for us to use ACPI
>> when needed in scsi?
> 
> We don't have ACPI bindings for generic SCSI devices. We have such
> bindings for SATA drives. You can put such things only in sr if it applies
> to all (maybe most) types of drives.

OK. Then these scsi bindings for sata drives will be pretty much of
no use I think.

> 
>> BTW, if sr_suspend should be generic, that would suggest I shouldn't
>> write any ZPODD related code there, right? Any suggestion where these
>> code should go then?
> 
> libata. Maybe some generic hooks can be called in sr_suspend().

Thanks for the suggestion.
The problem is, I need to know whether the door is closed and if there
is a medium inside. I've no way of getting such information in libata.

> PS: Are you sure sr_suspend() handles DVD-RAMs correctly?

No. Is there a spec for it?
Considering there are many different drives sr handle, is it possible to
write a generic sr_suspend?
Maybe your suggestion of callback is the way to go.
What about this idea, if we find this is a ZPODD capable drive, we
enable runtime suspend for it and write a suspend callback according to
ZPODD spec. For other drives that does not have a suspend callback, we
do not enable runtime suspend.
Does this sound reasonable?

Thanks,
Aaron