Oneiric: [PATCH] (UBUNTU: Sauce) Match jack input devices and pcm devices for HDMI

David Henningsson david.henningsson at
Wed Aug 31 07:18:33 UTC 2011

On 08/30/2011 03:48 PM, Tim Gardner wrote:
> On 08/30/2011 12:21 AM, David Henningsson wrote:
>> On 08/29/2011 06:08 PM, Tim Gardner wrote:
>>> On 08/29/2011 08:52 AM, David Henningsson wrote:
>>>> Upstream status for this patch is that Takashi went on vacation before
>>>> he commented on the patch, and might not return before kernel freeze.
>>>> Anyway, it's needed for jack detection for HDMI to work. So I'd be
>>>> happy
>>>> if we could apply this for Oneiric (the jack detection patches are
>>>> distro patches anyway), and then I'll have plenty of time to sort out
>>>> with Takashi what to do for P.
>>> While the patch looks fine, its difficult for me to ascertain the risk
>>> of regression. Has this patch had widespread testing? It appears to have
>>> the possibility for widespread impact.Without some really warm fuzzies
>>> from you (and a little data to back your claim), I'm inclined to let
>>> this go through the normal upstream process.
>> I'm not sure exactly what "warm fuzzies" you need, but currently:
>> * It has not had widespread testing. I could obviously test it on all
>> machines I have here, something I should probably do anyway, but would
>> that be enough for you?
>> * The upstream version of this patch, for Linux 3.2 (which is slightly
>> different, this is a backported version) has received review from
>> Stephen Warren at Nvidia, who has recently refactored the HDMI audio
>> driver. He believes the patch looks good, but was unsure if he wanted
>> more reformatting of the string at the same time.
> So, you're asking to have a patch applied that has general impact on all
> platforms with an HDMI port, which by your own admission has not had
> widespread testing, and has not been agreed to or fully reviewed by
> upstream maintainers.
> The kernel is in Beta freeze right now. What would your call be if you
> were in the same position?

If I were in the same position:

First and foremost, I would start with a warm, welcoming and encouraging 
attitude towards patches. A patch sent here, means someone not only 
wants to improve Linux in general, but also cares in special for Ubuntu, 
and has taken the time and effort to backport a patch to suit Ubuntu's 
particular kernel version. In this case, the patch author is a Canonical 
employee so this is not surprising, but nevertheless, this is a really 
good thing and should be encouraged.

With that positive attitude in mind, I would do a review. The review 
would, of course, take regression risk into account - a kernel bug can 
cause the system to fail in the most horrifying ways - but also weigh 
that against the possible positive outcomes of applying the patch, i e 
why it's needed in the first place. If I'm not qualified to make a 
review, I would find someone who is, to make the opinion for me.

The review in this case would notice that it impacts most people with 
working HDMI audio which means both higher risk and gain. OTOH, the code 
path is simple, which means that successful testing on one machine would 
make it unlikely to fail on another.

If I'm still unsure of regressions even after having done the review, I 
would make sure testing of the patch is done. If I have time, I do the 
testing myself, or if I don't, ask for someone to test it for me, but do 
what I can to help, e g by building a test kernel and provide 
instructions as of how to do the test. If testing with positive result 
is all that's needed before applying the patch, I would communicate that 
clearly, among with a deadline explaining when the testing must be 

David Henningsson, Canonical Ltd.

More information about the kernel-team mailing list