Re: [ECOS] Problem in cyg_io_compare?

[Jonathan Larmour <jifl at eCosCentric dot com>]

David N. Welton wrote:
> "Gary D. Thomas" <gary.thomas@mind.be> writes:
>
>
> > > 2) Document the existing behavior - "it's a feature, not a bug".
>
>
> > > I would be willing to contribute a documentation patch as well
> > > once I am sure I understand the underlying thought behind these
> > > functions.  I didn't find this either in the on-line
> > > documentation, or in my copy of Anthony Massa's book.
>
>
> > > Restating: it works as it does in order that the *name passed to
> > > the lookup function can be added to a 'base name' known to the
> > > driver to create a full name?
>
>
> > Yes, that's the intention, perhaps not very well documented or
> > articulated (I wrote that code oh so long ago...)
>
>
> How about something along these lines:

Although it may need a bit more glue, you can add this to 
io/common/current/doc/io.sgml at the end of the "how to write a driver" 
chapter (but before the how to write a serial hardare interface driver 
section) and send the patch (cvs diff -u) to ecos-patches. Thanks!

>   <para>
>     The <parameter>**tab</parameter> parameter holds a pointer to the
>     memory location of the devtab entry.  This indirection allows the
>     device driver author to create a new devtab entry in the lookup
>     function, in order to provide for pluggable devices, and devices
>     where multiple instances are possible.
>   </para>
> [snip]
> Of course, it needs some tweaking, as I'm not %100 sure on how **tab
> might be used, but adding that would be an improvement, especially WRT
> to the name parameter and it's "confusing" behavior.

:-). I think it's accurate. The idea is that something could return a 
completely different (perhaps artificially created i.e. not found in 
__DEVTAB__) handle pointing to a devtab entry for future accesses. 
Different cyg_devtab_entry_t means different function pointers etc. so it 
makes it quite generic. In practice, without a "cyg_io_close" this has 
some limitations.

I think your description is accurate though.

Jifl
--
eCosCentric    http://www.eCosCentric.com/    The eCos and RedBoot experts
--[ "You can complain because roses have thorns, or you ]--
--[  can rejoice because thorns have roses." -Lincoln   ]-- Opinions==mine


--
Before posting, please read the FAQ: http://sources.redhat.com/fom/ecos
and search the list archive: http://sources.redhat.com/ml/ecos-discuss