Re: USB problems
From: M. Warner Losh (imp_at_bsdimp.com)
Date: 12/30/04
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Date: Thu, 30 Dec 2004 11:16:31 -0700 (MST) To: jb@cimlogic.com.au
In message: <20041228010938.GA39686@freebsd3.cimlogic.com.au>
John Birrell <jb@cimlogic.com.au> writes:
: 1. The USB sub-system doesn't handle loading and unloading drivers properly.
: If a driver is unloaded when a USB device is still attached, the next
: time the driver is loaded, the kernel panics. This might not be such
: a problem to normal users because they don't have a need to do that, but
: during driver development when you want to load and unload repeatedly,
: it's a pain.
I don't see this. Can you give a more concrete example? I've done
work in this area and I believe that it is almost working correctly.
: 3. The usbd_bulk_transfer function calls tsleep() to wait for streaming
: data to become available. On current, this bumps into a KASSERT in
: msleep because Giant is not locked and no mutex has been supplied.
: In my driver, I need to run an 'encoder' thread which calls
: usbd_bulk_transfer() to gobble the incoming MPEG data stream. While
: this is going on, there is no syscall in progress because the
: application is off doing other things. It might be looking at the
: mmaped buffer or it may not.
:
: For FreeBSD, usbd_bulk_transfer() needs to change to allow the driver
: to specify it's mutex. I don't know what the implications are for
: uhci given that it hasn't been converted to use mutexes. Can anyone
: comment on that?
I have changes to make sure this can't happen as well. But you must
hold Giant whenever you call into the usb subsystem.
: I'd love to get rid of the attach_args structure and just pass a
: usbd_device_handle into the drivers, with struct usbd_device containing
: a couple of extra variables for use during matching.
I'd love to remove that attach_args and replace it with nothing.
: I'd like to remove the subdevs array from struct usbd_device under
: FreeBSD because the parent/child device tree should only be managed by
: bus routines. The relationship between a USB device and it's device_t
: should just be a field in struct usbd_device and it should be cleared
: when there is no device_t. Leaving a device_t hanging around when a
: driver had been unloaded is what is causing the panics I am seeing.
I'm working on this. However, many of the panics around this area
were fixed just before 5.3.
: I think that the uhub driver should have a uhub_driver_added routine rather
: than using the generic one. I'd really like to see the uhub code re-match
: vendor/product codes when a new driver is added, and if the new driver
: matches, then uhub should detach ugen and use the new driver. Similarly,
: when a driver is unloaded, if a USB device is still present, it should go
: back to ugen.
I already deal with these things, are you sure you're looking at the
current code? Well, I Don't deal with ugen, but when I have to load
drivers I don't include it in my kernel. There's no harm in that.
I'm working on a generic newbus way of dealing with this situation,
but acpi does non-idempotent things in its probe routines :-(.
Warner
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- Previous message: Rong-En Fan: "Re: 802.11 WPA and wpa_supplicant"
- In reply to: John Birrell: "USB problems"
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