On 12/07/2012 02:13 PM, Aaron Lu wrote:
> On 12/04/2012 08:11 PM, James Bottomley wrote:
>> On Mon, 2012-12-03 at 08:23 -0800, Tejun Heo wrote:
>>> Hello, James.
>>>
>>> On Mon, Dec 03, 2012 at 08:25:43AM +0000, James Bottomley wrote:
>>>>> 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.
>>
>> Can't we do that via an event? It's a bit clunky because we need the
>> callback in the layer that sees the sdev, which is libata-scsi, we just
>> need an analogue of ata_scsi_media_change_notify, but ignoring and
>> allowing polling is essentially event driven as well, so it should all
>> work. We'll need a listener in genhd, which might be trickier.
>
> Hi Tejun,
>
> Do you have any comments on James' suggestion? I want to know your
> opinion, thanks.
Hi Tejun,
A colleague of mine reminded me that it's impolite to write something
like this, and here is my apology. I didn't mean to be rude, I'm sorry
for this if it made you feel uncomfortable.
If possible, can you please shed some light on this problem and James'
suggestion? I need your opinions to make progress, thanks.
-Aaron
>
> Hi James,
>
> Do you mean we start a thread in genhd that listen to events, so that
> some driver can send an event to genhd about if the device should be
> polled? I'm thinking where to store such information. If store it in
> struct disk_events, then we will need to know which gendisk is for
> the device, but how? Maybe by loop scan all gendisk's driverfs_dev?
> If store it in struct device, then we do not need to send the event but
> just set a flag in sturct device in libata, and let genhd check this
> flag when poll. So I don't quite understand this, can you please
> elaborate? Thanks.
>
> Thanks,
> Aaron
>
>>
>> This may also work as the more generic route for stuff where we can't
>> connect the bottom to the top of the stack (which looks like a problem
>> we'll begin wrestling with a lot now).
>>
>> James
>>
>>
>
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