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From:   David Tomaschik <david@systemoverlord.com>
Date:   Fri, 7 Oct 2022 21:33:16 -0700
Message-ID: <CAOy4VzfHRD0cw2jdL=pzukc1QFuXgaC55Zst7uc-dMFPrHr7Yw@mail.gmail.com>
Subject: rtl8187 triggers usb device reset on kernel driver disconnect
To:     linux-wireless@vger.kernel.org, herton@canonical.com,
        htl10@users.sourceforge.net, Larry.Finger@lwfinger.net
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Hi all,

It seems that any time the rtl8187 driver is detached from an rtl8187
interface, a USB device reset is triggered.  This is not a problem in
the general case, but when working with libusb, calling
libusb_detach_kernel_driver
(https://libusb.sourceforge.io/api-1.0/group__libusb__dev.html#ga5e0cc1d666097e915748593effdc634a)
results in the device reset, which then causes the kernel driver to
re-attach to the device.  This prevents, for example, forwarding the
device into a VM using QEMU/KVM.  This seems to be due to
rtl8187_disconnect calling usb_reset_device.

The 8187 driver seems to be the only realtek driver unconditionally
resetting on disconnect -- is this technically necessary?  I'm not
sure I would call this a bug, but it's definitely behavior that was
very puzzling to me and I only understood after enough debugging to
start reading kernel source.

David

-- 
David Tomaschik
https://systemoverlord.com
david@systemoverlord.com
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