Re: Glib: Adding watch in the glib event poll

[Jacques Pelletier <jpelletier ieee org>]

On January 25, 2008 01:45:40 pm Jacques Pelletier wrote:
> Hi,
>
> I want to do a customized input routine for specialized hardware plugged
> into a parallel port. I don't have any device driver yet for this hardware.
>
> I have to poll bits; in my case, if the BUSY bit = 0, there's a character
> available on the data lines.
>
> I made my own version of add watch routines by copying the giounix.c code
> in glib and modifiying to my needs.
>
> Here are my questions:
>
> In giounix.c there is this:
>
> GSourceFuncs g_io_watch_funcs = {
>   g_io_unix_prepare,
>   g_io_unix_check,
>   g_io_unix_dispatch,
>   g_io_unix_finalize
> };
>
> Do I need to modify the g_io_unix_check routine for my needs also?
> static gboolean
> g_io_unix_check (GSource  *source)
> {
>   GIOUnixWatch *watch = (GIOUnixWatch *)source;
>   GIOCondition buffer_condition = g_io_channel_get_buffer_condition
> (watch->channel);
>   GIOCondition poll_condition = watch->pollfd.revents;
>
>   return ((poll_condition | buffer_condition) & watch->condition);
> }
>
> If I use it as is, it doesn't call my read_function.
> What is it supposed to check? While it's self documented, I don't get the
> higher picture.

For the record, I managed to make it work by making a copy of  g_io_unix_check 
and modifying for my needs. However, I don't know if it's "clean" code.

Here it is:
gboolean pt_8255_check    (GSource    *source)
{
  /* returns true if the /OBF line is asserted (==0) */
  return ((par_read_status(parallel_fd) & PAR_8255_RECV_MASK) == 0);
}

> --
> JP
>
>
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