Message-ID: <4623A391.9060604@linuxtv.org>
Date:	Mon, 16 Apr 2007 12:25:53 -0400
From:	Michael Krufky <mkrufky@...uxtv.org>
To:	CIJOML <cijoml@...ny.cz>
CC:	Michael Krufky <mkrufky@...uxtv.org>, Adrian Bunk <bunk@...sta.de>,
	video4linux-list@...hat.com, linux-kernel@...r.kernel.org,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	linux-dvb-maintainer@...uxtv.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [v4l-dvb-maintainer] [GIT PATCHES] V4L/DVB updates

CIJOML wrote:
> Dne pondělí 16 duben 2007 17:34 Michael Krufky napsal(a):
>   
>> Adrian Bunk wrote:
>>     
>>> On Sun, Apr 15, 2007 at 08:33:38PM -0400, Michael Krufky wrote:
>>>       
>>>> Mauro,
>>>>
>>>> I've been out of town for the past few days... I just got home and saw
>>>> this:
>>>>
>>>> Mauro Carvalho Chehab wrote:
>>>>         
>>>>>    - Fix 1/3 for bug 7819: fixed frontend hotplug issue
>>>>>    - Fix 2/3 for bug 7819: demux and dvr
>>>>>    - Fix 3/3 for bug 7819: fixed hotplugging for dvbnet
>>>>>           
>>>> I don't think that this is 2.6.21 material.  These patches have not yet
>>>> received
>>>> enough testing to be sent to mainline.
>>>>
>>>> I have tested them, and they seem to work for my cxusb device, but we
>>>> have yet to hear test results from users of usb dvb devices that do not
>>>> use the dvb-usb framework.  (ttusb, flexcop-usb, cinergyT2, for example)
>>>>
>>>> The bug that these patches fix has been around throughout the entire
>>>> kernel history of the dvb subsystem.  The bug is not a regression -- it
>>>> has always been
>>>> there.  In my opinion, it is too late in 2.6.21 development to apply
>>>> this change.
>>>> Because these fixes are not obvious, I think we should let them get some
>>>> more testing, and have them queued for 2.6.22 .
>>>>         
>>> Unless I misunderstand anything, this should fix [1].
>>>
>>> And this is a bug that was reported to be present in 2.6.21-rc but not
>>> in 2.6.20 (and it's therefore a regression, no matter whether the
>>> underlying problem was older and only exposed by some other change).
>>>       
>> Not true.  The DVB subsystem has NEVER been hot-unpluggable.  I confirm
>> that the patches SEEM to be correct, but this has not yet been verified. 
>> None of the authors of dvb-core gave their ACK on these changesets.
>>
>> The DVB hotplug issue has been around since the very beginning.  I assure
>> you, that I consider this fix to be very important, and I really would love
>> to see it hit mainline.  However, given the situation, it is not
>> appropriate to push these in during -rc7
>>
>> I have doubts on CIJOML's testing method -- there is no way he could have
>> unplugged the device while in use, while running 2.6.20.y and not receive
>> an OOPS.  CIJOML, please see the bottom of this email for
>>
>> Sure, this will prevent an OOPS on some, and hopefully all devices...  but
>> what if it causes a regression for those untested?
>>
>> Why do we have a merge window, if new changesets are going to be rushed
>> into late -rc kernels without proper testing, and without the ack of a dvb
>> subsystem maintainer?
>>
>> Are we prepared to go for another -rc and 3 or 4 weeks of testing to
>> confirm that this fix doesn't cause new regressions?  I don't think so.
>>
>> Markus Rechberger wrote:
>>     
>>> The patch has been around on the dvb mailinglist ([PATCH][RFC] DVB
>>> Hotplug Fix, 5. April 2007),
>>>       
>> The patch was merged into the development repository at the same time the
>> pull request was issued to Linus.  This has NOT been tested on a wide
>> scale.  It should go to -mm for a while before being merged to mainline.
>>
>> Mauro Carvalho Chehab wrote:
>>     
>>> I also explicitly warned at DVB ML that I were about to send this patch,
>>> together with other fixes, asking the community for more tests. After
>>> that, I received two positive answers on my mailbox from people that
>>> tested and noticed that this really fixed the issue.
>>>       
>> One of those positive answers was me -  I explained that it worked for me,
>> but we need others to test.
>>
>> You waited ONE DAY after sending this "warning" to the dvb mailing list?  (
>> http://linuxtv.org/pipermail/linux-dvb/2007-April/017204.html ) I saw that
>> email after seeing the pull request to Linus.  We dont have users testing
>> the repositories after each commit -- you _really_ need to give some more
>> time to allow for such testing.
>>
>> CIJOML wrote:
>>     
>>> Hi,
>>>
>>> I have tested these patches with:
>>>
>>> Freecom DVB-T dongle
>>> Pluto2 pcmcia card
>>> Leadtek WinFast DTV dongle 1st generation
>>> Leadtek WinFast DTV dongle 2nd generation
>>>
>>> These are 4 different devices with 4 different hw and modules.
>>> All works. Please apply.
>>>       
>> Well, that helps...  But it would still be nice to hear test results on a
>> CinergyT2 or flexcop-usb.
>>
>> Which driver supports those Winfast dongles?  We already know for sure that
>> the patches work correctly for any driver based on the dvb-usb framework.
>>
>> If you had the device open, and then disconnect it from the usb bus, no
>> matter what kernel version you're running, you should hit the OOPS.  I
>> confirm that these patches prevent that OOPS from occurring, but I have
>> trouble believing that you did NOT experience such an OOPS in 2.6.20.y
>>
>> Could you please describe the method in which your test caused an OOPS
>> using 2.6.21-rc and did NOT cause an oops in 2.6.20.y ?
>>     
>
> Hi,
>
> I have tested these patches with 2.6.20-mh1 + v4l-dvb-b5be3479f070 patchset.
> I also tried 2.6.21-rc6 + v4l-dvb-b5be3479f070 patchset and this combination 
> also works without OOPS.
>   
Yes, that shows that the changesets prevent the oops, but it says
nothing about vanilla 2.6.20.y
> Winfast dongles are both dvb-usb based (DiBcom 3000M-C and DiBcom DiB7000P), 
> but pluto2 is cardbus (pci) based.
>   
just as I figured.  The pluto2 test results are great to hear, though --
thank you.
> I think we can include these patches into 2.6.21 and if we receive any 
> problem, we still have 2.6.21.Z for fixing, don't we?

The stable kernel series is not there for that purpose.  It is not there
to encourage a rush of patches into a final kernel release, only to
cause potential problems, with the 2.6.x.y series as a fallback for
fixes.  We should avoid the need for such last-minute fixes wherever
possible.

-- 
Michael Krufky


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