[linux-dvb] Re: Kernel OOPS

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Holger Waechtler wrote:
> 
> Johannes Stezenbach wrote:
> 
> >  mws@renzel.net wrote:
> >
> > > i am playing around with the DVR device for playing back a TS which
> > > was recorded from the DVR device.
> >
> >  ...
> >
> > > The kernel is configured a an SMP Kernel and Preemptible feature.
> >
> >
> >  That's a recipe for disaster -- the dvr playback code in the av7110
> >  is seriously b0rked. Apart from the bug you found, the dvr device
> >  does not support non-blocking writes, and if you try to use multiple
> >  threads and do video ioctls from one thread while another thread
> >  blocks in dvr write() your machine will lock up...
> >
> > > The output from dmesg after Oopsing is :
> > >
> > > bad: scheduling while atomic! Call Trace:
> >
> >
> >  Just for the record, this is not an Oops, just an indication that the
> >  driver is buggy.
> >
> > > anybody you can help me out of this?
> >
> >
> >  The problem is that the av7110 hardware does not support TS playback.
> >  The driver tries to work around this by remuxing the TS into PES and
> >  feeding PES to the hardware. IMHO this code should be dropped rather
> >  than attempted to fix. Remuxing should be done in user space. VDR
> >  does the right thing.
> 
> calling the PES unpacking process a 'remuxing' is kind of flattered,
> not? Forcing everybody to misuse the lowlevel-API instead of highlevel
> access just because the av711x driver is broken...

Well, Holger, you keep repeating over and over that the av7110 driver
is "broken" and that this is "ancient" hardware and how great "modern"
hardware ist - but IMHO you totally neglect that the av7110 still is probably
the most widely used hardware! People have invested real money into these
full featured DVB cards and just don't want to throw them away.
Plus, there just isn't any reasonable alternative
And don't say "use a budget card and do replay over the graphics card" - the
average user wants to insert *ONE* card into his PC and use that one for
recording AND replay. Besides: replay over graphics card means MPEG decoding
in software, which in turn requires more CPU power... Also: are there any
budget cards already that have drivers that support CAMs? I have to admit that
I don't know that.

So, what about just fixing the av7110 driver?

SCNR

Klaus

> ...has the unlovely side
> effect that on well-designed hardware that can eat PS and TS directly
> the code will still do all the protocol handling and bit-twiddling on
> the host processor, the dedicated hardware will run idle.
> 
> The Avia processor and all modern STB CPUs can process multiplexed
> streams directly.
> 
> Holger


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