[linux-dvb] Re: Help on use of DMX_OUT_TAP (II)

[Johannes Stezenbach <js@convergence.de>]

Tim Wiffen wrote:

> I am not convinced that the poll method is better.  When I switched from
> GCC 2.95 to GCC 3.2 I found that dvbtune stopped being able to read PSI
> tables.  This code:
>
> struct pollfd ufd;
>
> ** SNIP **
>
> fd_pat = open(demuxdev[card],O_RDWR|O_NONBLOCK)
>
> ** SNIP **
>
> ufd.fd=fd_pat;
> ufd.events=POLLPRI;
> if (poll(&ufd,1,2000) < 0) {
>   fprintf(stderr,"TIMEOUT reading from fd_pat\n");
>   close(fd_pat);
>   return;
> }
> if (read(fd_pat,buf,3)==3) {
> 	
> ** SNIP **
You don't distinguish between read() returning success (> 0)
or error (-1). You also don't check ufd.revents. Please read the
manual pages for poll() and read() thoroughly.

> } else {
>  fprintf(stderr,"Nothing to read from fd_pat\n");
For the DVB driver read() can never return 0 (meaning end-of-file).
There must be something wrong with your system libraries or compiler.

> }
>
> Always returns "Nothing to read from fd_pat" when compiled on my system
> with GCC 3.2 but the binary compiled with GCC 2.95 works perfectly on
> the same system.  The error returned was always "Resource temporarily
> unavailable".
Odd.


Johannes




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