[linux-dvb] A bug in libdvben50221?

Christophe Thommeret hftom at free.fr
Fri Dec 5 02:02:52 CET 2008

Le jeudi 4 décembre 2008 23:58:31 Morgan Tørvolt, vous avez écrit :
> Hi all.
> This might be a stupid question, please feel free to call me a moron
> and tell me how to solve this little problem I am having. I have tried
> getting in touch with someone on the irc channel to help me sort this
> out without much luck. Hopefully someone here has some knowledge of
> the libdvben50221 library. I would imagine that very many use this
> library with their dvb cards, so there should be someone out there.
> The camthread in gnutv, which continuously polls the stdcam, calls the
> stdcam's poll function (obviously). The poll function is in my
> pointing to the en50221_stdcam_llci_poll function. This function in
> turn calls en50221_tl_poll, but without passing the return value of
> this on to the camthread function of gnutv. What happened in my case
> was that the transport layer crashed in some obscure way (this has
> only happened once actually), and the en50221_tl_poll function
> returned -1 all the time, and set the error state to be -3, which is
> EN50221ERR_TIMEOUT. It did not recover in over an hour of waiting.
> This message was spamming my console window:
> en50221_stdcam_llci_poll: Error reported by stack:-3
> After looking high and low for a way to be able to detect this state,
> I have come up with nothing. I cannot read the error value directly
> out of the stuct as it is a forward declaration in the header file and
> actually declared in the .c file. I can access the error data using
> the en50221_tl_get_error() function, but that only tells me that at
> some point there was an error with the given error value.
> At least on my cam I get this message often when I start a program:
> "en50221_stdcam_llci_poll: Error reported by stack:-7", which is a
> message I can test with. My testing suggest that the error is set to
> -7 and is left there until a new error occurs. In other words, it is
> not possible to detect if the error -7 occurs every second, every
> minute, or just once at the start and no errors since then. The same
> problem exists with the timeout error I had. gnutv could have detected
> that there had been a timeout error, but could in no way I can see,
> find out if it had resolved itself or not.
> The error I saw was a timeout error that happened after more than 24
> hours from starting the program, and the transport layer was returning
> -3 continuously.
> I can think of a few ways to solve this problem.
>  * One would be a callback function on transport layer error in the stdcam
>  * Have an error counter in the transport layer struct, and a function
> to read the counter. Must be reflected in the session layer as well it
> seems.
>  * Return the transport layer poll's return value in some way from the
> stdcam poll function. Possibly by setting adding to the stdcam_status
> enum a value like "EN50221_STDCAM_TL_ERROR". Maybe a bitshifted value
> as well? It should then be easy to check the error using the
> en50221_tl_get_error function.
>  * This is already solved trough some other solution, and I have been
> to blind to see it all along.
> I prefer the options from bottom to top.
> Any takers?

Look at en50221_stdcam_llci_poll(..) in the joined file.
This is how i solved that.

Christophe Thommeret
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