Pseudo-device driver & select ??

[Aziz Kezzou]

> >
> > Aziz Kezzou wrote:
> > > Hi all,
> > > I am trying to implement a small kld pseudo-device driver on FreeBSD 5.3 that
> > > behaves just like a socket with regards to the select system call.
> > >
> > > Currently, I am using the sample echo pseudo-device driver from
> > > http://www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/driverbasics-char.html
> > >  as an example. However, whenever  I call select on the file
> > > descriptor of "/dev/echo" it always returns even when there is no data
> > > to be read.
> > >
> > > I looked at the socket code and it looks like I need to provide my own
> > > "fo_select" function in the fileops data structure. Am i right ? How
> > > do I do that ? The sample echo pseudo-device driver above uses
> > > "struct cdevsw"  instead...
> > >
> > > Thanks
> > > -aziz
> > > _______________________________________________
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> > >
> > >
> > look at spec_poll()
> > I beleive that when your device is opened the fileops{} will
> > point to the spec ops and you're code will be entered via
> > spec_poll() - now you just need to implement the poll/select notion
> > for your device.
> >
> 
> Thanks,
> Actually, il turned out to be very simple.
> I needed only to provide a "d_poll" function as part of the structure
> cdevsw, as follows :
> 
> /* Character device entry points */
> static struct cdevsw echo_cdevsw = {
>     .d_version = D_VERSION,
>     .d_open = echo_open,
>     .d_close = echo_close,
>     .d_read = echo_read,
>     .d_write = echo_write,
>     .d_poll = echo_poll,
>     .d_name = "echo",
> };
> 
> with echo_poll :
> static  int
> echo_poll(struct cdev *dev, int events, struct thread *td)
> {
> 
>   uprintf( "echo_poll called : data_available = %d!\n", data_available );
>   if(data_available == 0)
>     return 0;
>   data_available = 0;
>   return 1;
> }
> 

Now the question is, if I don't have any data available when select
(i.e d_poll ) is called, how do I notify select  when data arrives ?
looks like "d_poll" is called only once (the name is a bit misleading
here ;-) , isn't it ?

Any hints ? 
Thanks.
-aziz