linux-kernel - Re: RFC: btusb firmware load help

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Message-ID: <20101006163816.GE7070@tux>
Date:	Wed, 6 Oct 2010 09:38:16 -0700
From:	"Luis R. Rodriguez" <lrodriguez@...eros.com>
To:	Marcel Holtmann <holtmann@...ux.intel.com>
CC:	Luis Rodriguez <Luis.Rodriguez@...eros.com>,
	linux-bluetooth <linux-bluetooth@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	Deepak Dhamdhere <Deepak.Dhamdhere@...eros.com>,
	Sree Durbha <Sree.Durbha@...eros.com>
Subject: Re: RFC: btusb firmware load help

On Wed, Oct 06, 2010 at 08:56:06AM -0700, Marcel Holtmann wrote:
> Hi Luis,
> 
> > > Now I am failing to understand why this was done wrong in the first
> > > place. Especially if the loading procedure happens as you say it
> > > happens.
> > 
> > You got me :) Anyone?
> > 
> > > This is the example for the Broadcom 203x devices:
> > >
> > > static struct usb_device_id blacklist_table[] = {
> > >        /* Broadcom BCM2033 without firmware */
> > >        { USB_DEVICE(0x0a5c, 0x2033), .driver_info = BTUSB_IGNORE },
> > >
> > > The btusb driver clearly blacklists them. And then bcm203x can take over
> > > loading the firmware:
> > >
> > > static const struct usb_device_id bcm203x_table[] = {
> > >        /* Broadcom Blutonium (BCM2033) */
> > >        { USB_DEVICE(0x0a5c, 0x2033) },
> > >
> > > So there is a working example of this already in the kernel tree since
> > > forever.
> > 
> > Nice, thanks for the pointer. Our team will review and try to address
> > an alternative patch.
> > 
> > Now for my own sanity -- I still don't think I get this how this
> > BCM2033 blacklist trick works, I take it the device once plugged in
> > gets a generic btusb USB device vendor:device ID. The btusb driver
> > then picks up the the blacklist table, and searches for a
> > usb_match_id() on it for the given interface... What I don't get is
> > how there will be a match here if the USB vendor:device ID is just the
> > generic btusb one. Can you help me understand how this trick works?
> 
> the generic Bluetooth USB class descriptors is what btusb uses. With a
> few expectation for devices that use VID:PID combination.

Ahhh... got it..

> So in general what happens if a device gets matched via the Bluetooth
> USB class descriptors the btusb driver will claim. We do however check
> against out blacklist first. If the VID:PID is listed in the blacklist
> we do return ENODEV. That means that the USB subsystem goes ahead and
> tries the next driver. In this case bcm203x driver. This will claim it,
> load the firmware, reset it and come back with different VID:PID values.
> After that the btusb can successfully claim it since it is no longer in
> the blacklist.

Ah neat.

> If I understand this all correct without having the hardware available
> for verifying this, then it should be like this:
> 
> Just add this to blacklist_table[] in btusb.c:
> 
>         /* Atheros AR3011 without firmware */
>         { USB_DEVICE(0x0cf3, 0x3002), .driver_info = BTUSB_IGNORE },
> 
> And then we can add the firmware loading to ath3k driver to load the
> specific 1st stage firmware. And then ath3k can load the 2nd stage as
> well. After that it should become a default Bluetooth USB device and the
> btusb driver can take care of it.

Got it... thanks for the clarification. So ath3k actually doesn't seem to
have 2-stage firmware files, ath3k-2.fw actually seems to be a new firmware
upgrade. The firmware already made it into linux-firmware.git tree but the
respective patch just never made it upstream. I am not sure of the
differences between these firmware but I do remember reading from Vikram
that no new API was changed. I asked for clarification on the firmware
updates and asked if it can be documented here:

http://wireless.kernel.org/en/users/Drivers/ath3k

If the device can live with simply getting ath3k-1.fw loaded once then
perhaps the change you described above is all that is needed, not sure.

Deepak, can you please try this patch, I don't have hardware to test
this with.

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index d22ce3c..a62c1b2 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -140,6 +140,9 @@ static struct usb_device_id blacklist_table[] = {
 	/* Frontline ComProbe Bluetooth Sniffer */
 	{ USB_DEVICE(0x16d3, 0x0002), .driver_info = BTUSB_SNIFFER },
 
+	/* Atheros AR3011 without firmware */
+	{ USB_DEVICE(0x0cf3, 0x3002), .driver_info = BTUSB_IGNORE },
+
 	{ }	/* Terminating entry */
 };
 
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