On Thu, 30 Mar 2000, Johannes Erdfelt wrote:
> On Thu, Mar 30, 2000, Matthew Dharm <[EMAIL PROTECTED]> wrote:
> > How do I do, from kernel space, a port reset on a device? Apparently
> > there are some devices (ie a CD-ROM which is reading from a dirty disk)
> > which will get into a jammed state and require a port reset to un-jam it.
> >
> > At least, according to the spec, a port reset is the "more drastic action"
> > that I should try next.
> >
> > So, how do I do this?
>
> Nonexistant right now. The code to do it would look something like this:
>
> int usb_reset_device(struct usb_device *dev)
> {
> struct usb_device *parent = dev->parent;
> int i;
>
> for (i = 0; i < parent->maxchild; i++) {
> if (parent->children[i] == dev)
> usb_set_port_feature(parent, i,
> USB_PORT_FEAT_RESET);
> }
>
> return 0;
> }
>
> I haven't tested the code (not even tried compiling it), but I think it
> should work. I know the above code won't work on a root hub (it'll
> oops).
Hrm... we'll need a solution that works on root hubs, also.
Does someone want to volunteer to test this code this weekend? Perhaps
someone with a bus scope?
> The device should disconnect and then reconnect. This will cause it to
> go through the normal connect and disconnect code paths. This means that
> dev, after calling the function is invalid.
Will this disconnect and reconnect be serialized? Transactions which go
through hubs are serialized, so I expect so. But I've been wrong before,
so I want to ask explicitly.
Also, will the disconnect and reconnect occur before the function returns?
Just the disconnect? Neither?
> usb_set_port_feature is part of hub.c (declared static) so you may want
> to throw the function in hub.c and export the symbol from there.
Probably a good idea. Or, perhaps it could go into usb.c -- tho in either
case it winds up in the core module.
Matt Dharm
--
Matthew Dharm Home: [EMAIL PROTECTED]
Engineer, Qualcomm, Inc. Work: [EMAIL PROTECTED]
It was a new hope.
-- Dust Puppy
User Friendly, 12/25/1998
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