RTEMS sound device driver

[Joel Sherrill]

Pattara Kiatisevi wrote:
> 
> OK, meanwhile I am trying this static method as you suggested while
> waiting for the new dynamic one. (In the hope also to understand more
> about RTEMS)
> 
> 1.I created sound.h in my local application directory containing:
> 
> #define SOUND_DRIVER_TABLE_ENTRY \
>   { sound_initialize, sound_open, sound_close, \
>     sound_read, sound_write, sound_control }
> and the declarations of these 6 functions (copied from in console.h).
> 
> 2.I created sound.c containing:
> 
> rtems_device_driver sound_initialize(
>   rtems_device_major_number  major,
>   rtems_device_minor_number  minor,
>   void                      *arg
> )
> {
>   rtems_status_code status;
> 
>   /*
>    *  Register Device Names
>    */
> 
>   status = rtems_io_register_name( "/dev/dsp", major, 0 );
>   if (status != RTEMS_SUCCESSFUL)
>     rtems_fatal_error_occurred(status);
> 
>   /*
>    *  Initialize Hardware
>    */
> 
>   return RTEMS_SUCCESSFUL;
> }
> 
> For the rest 5 functions, I just have "return RTEMS_SUCCESSFUL;" inside.
> 
> 3.In my application header, I have such thing like this:
> 
> [cut]
> #define CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE
> 
> #define CONFIGURE_MAXIMUM_DRIVERS 10


> #include <console.h>
> #include "sound.h"
> 
> rtems_driver_address_table Device_drivers[] = {
>         CONSOLE_DRIVER_TABLE_ENTRY,
>         SOUND_DRIVER_TABLE_ENTRY,
>         { NULL, NULL, NULL, NULL, NULL, NULL }
> };
> 
> #include <confdefs.h>
> 
> [cut]
> 
> #define open_mode 1
> #define DEVICE_NAME "/dev/dsp"
> 
> [cut]
>   /* Open sound device */
>   if ( (audio_fd = open(DEVICE_NAME, open_mode, 0) ) == -1 ) {
>     /* open of a device failed */
>     perror(DEVICE_NAME);
>     exit(1);
>   }
> 
> Then I compiled and ran the code and got this error:
> 
> /dev/dsp: Too many open files in system
> 
> Do you have any clues?

The error message was actually right in this case. :)

By default, RTEMS only provides 3 file descriptors (stdin, out, 
and error).  

#define CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS XXX

where XXX is some number greater than 3. :)

> Thank you very much,
> Pattara
> 
> On Thu, 7 Feb 2002, Aaron J. Grier wrote:
> 
> > On Fri, Feb 08, 2002 at 12:02:33AM +0100, Pattara Kiatisevi wrote:
> >
> > > But how exactly is this "registering" process? I took a look at the
> > > existing driver code as suggested and draft the steps as follow.
> >
> > rtems_io_register_name binds a name in filesystem space to the device
> > driver.
> >
> > > -I create a file contained device driver's code: sound-driver.c
> > >     -Which should contain initialize(), open(), close(), read(),
> > > write(), and control(). Arguments of these functions = like in console.c?
> >
> > yes.
> >
> > >     -In the initialize() I would have sth. like:
> > >
> > >     rtems_io_register_name( "/dev/dsp", major, 0 );
> > >
> > > -In my application file, I do open(), ioctl(), write(), close() to
> > > /dev/dsp as usual.
> >
> > you understand correctly.
> >
> > > -And then how can I tell RTEMS to call this sound device driver when there
> > > is access to /dev/dsp?
> >
> > after registering the device with rtems_io_register_name, you can
> > perform standard operations like open(), close(), lseek(), dup(), etc.
> > on your file.  RTEMS handles the "mid level" between these calls and
> > your device driver calls.
> >
> > > Something to do with #def CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE and I
> > > have to create my own Device_drivers? (Hmm, but how and where? :) )
> >
> > look at c/src/lib/include/console.h.  you define a table entry, and the
> > extern declarations for your driver entry points, then somewhere in your
> > confdefs.h:
> >
> > #define CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE
> >
> > #include <console.h>
> >
> > rtems_driver_address_table Device_drivers[] = {
> >         CONSOLE_DRIVER_TABLE_ENTRY,
> >         { NULL, NULL, NULL, NULL, NULL, NULL }
> > };
> >
> > getting everything glued in to autoconf/automake so that they will be
> > compiled and linked into your BSP is a whole other story.  :)  let us
> > know if you need help with that.
> >
> > --
> >   Aaron J. Grier  |   Frye Electronics, Tigard, OR   |  aaron at frye.com
> >      "In a few thousand years people will be scratching their heads
> >        wondering how on earth the first computer was invented and
> >           bootstrapped without a prior computer to do it with."
> >                     --  Chris Malcolm, on comp.arch
> >
> >

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
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