linux-kernel - Re: [PATCH v2] usb: serial: Repair FTDI FT232R bricked eeprom

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Date:   Fri, 11 Sep 2020 08:09:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Hector Martin <hector@...cansoft.com>
Cc:     James Hilliard <james.hilliard1@...il.com>,
        Johan Hovold <johan@...nel.org>,
        Lars Melin <larsm17@...il.com>,
        Oliver Neukum <oneukum@...e.de>, linux-usb@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Russ Dill <Russ.Dill@...il.com>
Subject: Re: [PATCH v2] usb: serial: Repair FTDI FT232R bricked eeprom

On Fri, Sep 11, 2020 at 04:54:08AM +0900, Hector Martin wrote:
> On 11/09/2020 03.51, James Hilliard wrote:
> > I haven't tested this yet but my assumption was that either a kernel driver
> > or libusb can issue usb control messages, but both can not be bound to
> > a device at the same time. I figured this wouldn't have come up when you
> > tested your python script since the script likely predated adding the brick PID
> > to the ftdi_sio Linux kernel driver.
> 
> Binding to interfaces is exclusive, but global device control messages are
> not issued to an interface. I think it should work even if the kernel driver
> is bound (this is how lsusb works too, since it issues control requests even
> to devices bound to drivers). Even if it is necessary to unbind it, though,
> libusb already provides a single function to do that
> (libusb_detach_kernel_driver).

You really should unbind the device from the driver when doing stuff
like this, so the kernel doesn't get confused.

thanks,

greg k-h