linux-kernel - Re: [PATCH 1/1] media: dvb-usb/af9015, fix disconnection crashes

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Date:	Tue, 26 Jan 2010 14:08:45 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Antti Palosaari <crope@....fi>
Cc:	Jiri Slaby <jirislaby@...il.com>, mchehab@...radead.org,
	linux-kernel@...r.kernel.org,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	linux-media@...r.kernel.org, Pekka Sarnila <sarnila@...t.fi>
Subject: Re: [PATCH 1/1] media: dvb-usb/af9015, fix disconnection crashes

On Mon, 25 Jan 2010, Antti Palosaari wrote:

> > What happens if you disable the HID layer? Or at least if you add an
> > ignore quirk for the device in usbhid?
> 
> Looks like Fedora doesn't have usbhid compiled as module. I looked
> hid-quirks.c file and there was only one af9015 device blacklisted 15a4:9016.
> I have 15a4:9015, 15a4:9016 and 13d3:3237 devices and no difference.
> 
> How can I disable HID layer?

In case usbhid is compiled in, you should still be able to force the 
ignore quirk by passing

	usbhid.quirks=0x15a4:0x9015:0x04

to kernel boot commandline.

> > I forbid usbhid to attach to the device, as the remote kills X with HID
> > driver. With dvb-usb-remote it works just fine (with remote=2 for af9015
> > or the 4 patches I've sent).
> 
> In my understanding the cause of the remote problem is chipset bug which sets
> USB2.0 polling interval to 4096ms. Therefore HID remote does not work at all
> or starts repeating. It is possible to implement remote as polling from the
> driver which works very well. But HID problem still remains. I have some hacks
> in my mind to test to kill HID. One is to configure HID wrongly to see if it
> stops outputting characters. Other way is try to read remote codes directly
> from the chip memory.

Yes, Pekka Sarnila has added this workaround to the HID driver, as the 
device is apparently broken.

I want to better understand why others are not hitting this with the 
DVB remote driver before removing the quirk from HID code completely.

> But all in all, your patch does not break anything, it is safe to add. It
> could be still nice to know if there is better alternatives. And there is
> surely few other devices having HID remote - are those also affected.

-- 
Jiri Kosina
SUSE Labs, Novell Inc.

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