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Subject: Re: loading firmware while usermodehelper disabled.
From: Jack Stone <jwjstone@fastmail.fm>
Date: Tue, 03 Jan 2012 00:22:58 +0000
To: Matthew Garrett <mjg@redhat.com>
CC: Linus Torvalds <torvalds@linux-foundation.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Oliver Neukum <oliver@neukum.org>, Dave Jones <davej@redhat.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Larry Finger <Larry.Finger@lwfinger.net>,
        Chaoming Li <chaoming_li@realsil.com.cn>,
        "John W. Linville" <linville@tuxdriver.com>,
        Greg Kroah-Hartman <gregkh@suse.de>,
        USB list <linux-usb@vger.kernel.org>,
        Linux Wireless List <linux-wireless@vger.kernel.org>
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Matthew Garrett <mjg@redhat.com> wrote:

>On Mon, Jan 02, 2012 at 11:31:55PM +0000, Jack Stone wrote:
>
>> Rather than merging the drivers we could make the uvcvideo (or any
>other
>> generic driver) driver expose a "subdriver" interface that allows
>> another module to bind to the specific ID and add extra handling to
>> certain events. We could then use that interface to provide a
>firmware
>> driver for each device that needs it. The firmware driver could bind
>to
>> the bootstrap device and to the uvcvideo subdriver interface and it
>> would then have all the lifetime info we need. [Credit to Linus for
>> suggesting this idea]
>
>No, the uvcvideo driver would need to call out to load the firmware 
>loader driver, otherwise you'll never know to load the firmware loader 
>driver.

So we have a table of USB ids that list the devices that need firmware drivers. When the uvcvideo driver registers the firmware interface with a USB id that matches the list we load the firmware driver and pass it a "warm start" event so it can cache the firmware.

As long as we can identify the devices that *might* need firmware then we are ok.

Thanks,

Jack

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