Date: Thu, 17 Mar 2005 00:27:44 -0500
From: Gene Heskett <gene.heskett@verizon.net>
Subject: Success! was Re: tvtime audio vs pcHDTV-3000 card and pvHDTV-1.6
 software
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       Linux and Kernel Video <video4linux-list@redhat.com>
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On Wednesday 16 March 2005 20:15, Gene Heskett wrote:
>Greetings;
>
Here I go, talking to myself again.  Please read on.

>I've spent a goodly part of the last 3 hours rebooting, to find out
>where this audio control function died, and I think now I can point
>an accusatory finger at the 2.6.11.2 patch with some degree of
>certainty.
>
>The scenario goes like this:
>
>reboot to 2.6.11-rc5, everything works flawlessly except the 1394
>stuff, that kernel didn't have it built in yet.
>
>reboot to 2.6.11+bk-ieee1394.patch  everything works flawlessly
>
>reboot to 2.6.11.1+bk-ieee1394.patch everything works flawlessly
>
>reboot to 2.6.11.2+bk-ieee1394.patch tvtime has no volume control,
> and the sound gets very very tinny about 1 second after it starts
>
>This scenario continues up to and includeing 2.6.11.4.
>
>So now my next question is, how to I clean up those src trees so
> that a diff actually outputs only the src code differences, thereby
> allowing a simple diff -urN (or whatever is the recommended command
> line to do a recursive diff on the whole maryann) to disclose the
> real diffs.  In other words, is a simple 'make clean' sufficient?
>
>I got the impression from a comment that was made, that quite a body
>of work was actually done, in the i2c area, that somehow does not
>show in the changelog, nor in that simple little 10 line patch that
>was 2.6.11.2.  And how that little patch could be responsible for
>breaking this boggles what tiny little miniscule piece of a mind I
>have left at this point.
>
>If thats the case, then how did it get into my src code tree since
> the exact same 2.6.11.tar.gz was used as the base for applying each
> of the incrementals to each of the src trees I now have sitting in
> /usr/src?  Good question that...
>
>Unforch, the 2.6.11 plain tree has not, in this case been built yet
> as it got accidently nuked by a missfire of my 'buildit26' script,
> which normally moves a base version tree out of the way before it
> unpacks a fresh copy, and then renames that tree to be the current
> version and then restores the base tree to its original name.
>
>Thats not the one I want to use as the 'gold standard' anyway.
>2.6.11.1 works, and 2.6.11.2 doesn't.  So at this point, 2.6.11.1 is
>the 'gold standard'.
>
>But, both the 2.6.11.1 and the 2.6.11.2 trees are as built, and the
>diff I got was far larger than forgetting to apply the
>bk-ieee1394.patch to one of them would account for.  Many tens of
>kilobytes in fact.
>
>Please throw me a bone here folks.

Pursuant to checking out that it was 2.6.11.2 that broke it, I just 
built and rebooted to a 2.6.11.5 kernel, but without the 2.6.11.2 
patch.

It all works exactly as it should!!!!!!!!

So now the $64K question is, how could this little patch screw that up 
so frigging bad?
----------------------
diff -Nru a/Makefile b/Makefile
--- a/Makefile 2005-03-09 00:13:29 -08:00
+++ b/Makefile 2005-03-09 00:13:29 -08:00
@@ -1,7 +1,7 @@
 VERSION = 2
 PATCHLEVEL = 6
 SUBLEVEL = 11
-EXTRAVERSION = .1
+EXTRAVERSION = .2
 NAME=Woozy Numbat
 
 # *DOCUMENTATION*
diff -Nru a/fs/eventpoll.c b/fs/eventpoll.c
--- a/fs/eventpoll.c 2005-03-09 00:13:29 -08:00
+++ b/fs/eventpoll.c 2005-03-09 00:13:29 -08:00
@@ -619,6 +619,7 @@
  return error;
 }
 
+#define MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
 
 /*
  * Implement the event wait interface for the eventpoll file. It is 
the kernel
@@ -635,7 +636,7 @@
        current, epfd, events, maxevents, timeout));
 
  /* The maximum number of event must be greater than zero */
- if (maxevents <= 0)
+ if (maxevents <= 0 || maxevents > MAX_EVENTS)
   return -EINVAL;
 
  /* Verify that the area passed by the user is writeable */
------------------
And this patch looks perfectly good and proper to me IF indeed 
MAX_EVENTS is properly defined as some positive value.  I personally 
don't write code that doesn't check both ends of a boundary 
condition, in C or assembly.  Did anybody stick a printk in there to 
check?

Call me whatever, but leaving out the above patch fixes it right up.  
My guess is that somehow, MAX_EVENTS is not being properly declared?
And why didn't it bother a whole bunch of stuff in that case?  Why 
just tvtime?

A side comment on the 9 piece 2.6.11.5 kit from earlier this evening 
which I merged into one file and applied.  Nobody fixed the Makefile, 
so I had to build it twice.  Minor nit, but I wonder how many others 
rebooted to it to be greated by a dozen screens full of missing 
modules messages scrolling by at around 10+33rd fenceposts per 
mile. :)

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
99.34% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com and AOL/TW attorneys please note, additions to the above
message by Gene Heskett are:
Copyright 2005 by Maurice Eugene Heskett, all rights reserved.
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