Re: [linux-usb-devel] Re: [PATCH] USB changes for 2.5.58

[Doug Ledford <dledford@redhat.com>]

On Fri, Jan 24, 2003 at 02:59:10PM -0800, Mike Anderson wrote:
> Doug,
> 	I started writing the interface you put forth in your email. I
> 	am currently debugging it in UML so I can generate the error
> 	conditions in a control manner.

Very cool!  Thanks Mike.

>	 I still have some stuff to look
> 	at in the error handler with it running in this mode as it
> 	previously expected no one else to be possibly doing operations
> 	on the host. This could be the case if other LLDD's use this
> 	interface and have another device that happens to timeout an IO
> 	post a device being set offline.

Unless someone changed things behind my back, we still have on eh thread 
per host don't we?  As such, since each device is it's own host in USB 
(and I think in ieee1394 as well), this shouldn't be an issue...

> A clarification question below.
> 
> 
> Doug Ledford [dledford@redhat.com] wrote:
> 
> > So, what you should be doing in 
> > order to be both a nice scsi host that plays well with the generic 
> > mechanism we have in place is when you get this removal event, you should 
> > be free'ing all the state you needed about the usb bus and such and taking 
> > this usb device off line or whatever you do.  Then let the scsi mid layer 
> > clean up at it's leisure.  You don't need to worry about it because the 
> > only thing you will have left is to wait for the scsi subsys to call you 
> > when it's time to delete things.  You don't even have to keep device 
> > references around because we pass those in to your deletion routines 
> > anyway.
> > 
> > > I want to be able to inform the SCSI mid-layer, which will then inform
> > > higher layers, that the device is gone.
> > 
> > scsi_set_device_offline() as we've been discussing.
> > 
> 
> I assumed that the hotplug event would only come from this function if
> no commands where outstanding. If there where commands outstanding the
> event would not be generated until the error handler gained ownership of
> all the commands.

Yes.  But more than that, we really want to also make sure that the 
current request queue for the device is empty of all commands before 
sending the hot plug event.

-- 
  Doug Ledford <dledford@redhat.com>     919-754-3700 x44233
         Red Hat, Inc. 
         1801 Varsity Dr.
         Raleigh, NC 27606