[linux-dvb] Re: Avermedia DVB-T oops

[Holger Waechtler <holger@convergence.de>]

Jamie Honan wrote:
> On Sun, Nov 09, 2003 at 10:52:07AM +1000, Wayne Parrott wrote:
>
> > Although that seems like a good change it didn't fix the problem.
> > I have tried calling printk to see the data in sp887x_firm and the oops  
> > happens on the printk line so I am sure it has something to do with  
> > that variable.
> > BTW shouldn't the BUFSIZE problem be causing a seg fault for everyone  
> > else? or is kernel mode unprotected or something?
>
> The declaration for integer i on the stack following probably
> has something to do with it.
>
> I notice that sp887x_initial_setup called from an ioctl init,
> yet the declaration for sp887x_firm is __devinit in sp887x_firm.h.
>
> Either the __devinit has to be removed, or firmware uploaded inside
> another compatible function when the module is loaded.
the __devinit flag remains from a time where the firmware was loaded at 
module initialisation time. This has changed since it caused modprobe to 
hang for a few seconds under some circuimstances and caused oopses if 
the USB device was removed while modprobing the driver. I would vote for 
removing the __devinit flag.

> Hmm, this module is also marked GPL, with the firmware embedded
> as data ....
:) feel free to implement the firmware loader code - this driver was a 
quick hack to get things running...


> As to why no-one else has seen this:
>
> At the moment, DVB in Linux presents considerable challenges
> for an ordinary user. The whole szap/tzap / scan thing needs
> to be reworked.
scan/szap/czap/tzap were written as example code and never intended to 
act as production tools or enduser tools. We needed a few simple 
programs that are verbose and simple enough to trace installation 
problems - nobody expects you to use this code in everyday use.

And we wanted to provide a reference implementation to show how the API 
could be used.

> What I have in mind is a library that can do pretty much what
> scan / zap does. That library can then be used by GUI's,
> command line tools, scripting languages, dialog style tools etc. 
> Or does such a beast exist and I've missed it?
there exist some approaches like this: the Metzlerbros libdvb 
(http://www.metzlerbros.org/dvb/index.html), the dvbsak project on 
sourceforge (http://dvbsak.sourceforge.net/), libdvb++ in the dbox2 
project 
(http://cvs.tuxbox.org/cgi-bin/viewcvs.cgi/tuxbox/apps/dvb/libdvb%2B%2B/). 
But none of them has been widely accepted in the past, as far I know 
none of them is used by a really big project yet...

Usually it does not makes much sense to write a killer library without 
the background of a killer application -- you should not encapsulate 
things without the need for abstraction, otherwise you'll have to work 
hard later when you have to access functionality that has been 
'abstracted away' because the library designer tagged it as 
'non-important for highlevel developers'.

Holger



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