cvs commit: src/sys/cam/scsi scsi_da.c src/sys/dev/usb umass.c usbdevs

[Nate Lawson]

Scott Long wrote:
> Matthew Jacob wrote:
>>>>
>>>> And how will you distinguish between "not currently enabled" and 
>>>> "not supported"?
>>>>
>>>
>>> If WCE is not supported, will the device lie and report the WCE bit as
>>> set?
>>>
>>
>> No. But a device could have it turned off and you wouldn't then infer 
>> that you *could*.
> 
> 
> I guess I don't follow.  There was a suggestion to read page 8 during 
> the da device probe, cache the WCE value, and act on it accordingly
> later on.  There was also a suggestion to read the page on demand as
> part of the immediate decision to do the SYNC CACHE.  As much of a
> hassle as it could be, the latter is likely the better approach as it
> eliminates the messy state tracking that you'd have to do on the user.
> Who wants to hack up the pass driver to trap mode page writes and then
> try to correlate which da device to pass that info on to?  And yeah,
> if the device is able to change the state on its own, there is no
> way the first approach can work.

I agree -- we should just do the MODE SENSE inline with the SYNC CACHE 
each time for starters.  If it causes problems, then re-evaluate this 
approach.  Can someone with a bad USB device run the appropriate 
camcontrol command to see if WCE is set or not?  It would help to know 
if they lie because if so, this approach is not likely to succeed.

-- 
Nate