What's VRAM?

Thanks,
Michael

-----Original Message-----
From: port-dreamcast-owner@netbsd.org
[mailto:port-dreamcast-owner@netbsd.org]On Behalf Of Yasushi Oshima
Sent: Wednesday, February 05, 2003 7:06 AM
To: port-dreamcast@netbsd.org
Subject: Re: X under netbsd/dreamcast



Marcus Comstedt <marcus@mc.pp.se> wrote:

>> Do you have some simple example on how to mmap the framebuffer?
>
> IIRC, it was something along the lines of
>
>   int fd;
>   unsinged short *ptr;
>   int gfx_mode = WSDISPLAYIO_MODE_MAPPED;
>   int text_mode = WSDISPLAYIO_MODE_EMUL;
> 
>   /* Open the device */
>   fd = open("/dev/ttyE0", O_RDWR);
> 
>   /* Switch to graphics mode */
>   ioctl(fd, WSDISPLAYIO_SMODE, &gfx_mode);
> 
>   /* Map the framebuffer */
>   ptr = mmap(NULL, 640*480*2, PROT_READ|PROT_WRITE, MAP_SHARED,
>              fd, 0);
> 
>   /* Draw on screen using ptr...*/
> 
>   /* Go back to text mode (don't forget this!) */
>   ioctl(fd, WSDISPLAYIO_SMODE, &text_mode);
> 

Does this work fine under the current kernel?

I'm trying to access VRAM like this now, but it does not work
on my Dreamcast.
mmap(2) returned with an address (it is 0x20410000), however
the process became hangup when accessing this area.


   unsigned short x;

   if (ioctl(fd, WSDISPLAYIO_SMODE, &gfx_mode) < 0)
      err(1,"ioctl"); 

   ptr = mmap(NULL, 640*480*2, PROT_READ|PROT_WRITE, MAP_SHARED,
              fd, 0);
   if ( ptr == MAP_FAILED) {
                ioctl(fd, WSDISPLAYIO_SMODE, &text_mode);
                err(1,"mmap");
   }

   x = *ptr;    /* <------   hangup here ------- */

   ioctl ( fd, WSDISPLAYIO_SMODE, &text_mode);

   print ("addr  = %p\n", ptr);
   print ("*addr = %x\n", x);

The CPU load of this process became about 100% by top(1).

|  PID USERNAME PRI NICE   SIZE   RES STATE      TIME   WCPU    CPU COMMAND
|  835 root      64    0   144K   64K RUN        1:23 99.43% 97.95% pvrtest

When hit Ctrl-C, this process has terminated. 
Console has been still graphics mode after terminating.

I use 1.6N kernel (cross built on NetBSD/i386 at Feb 4).

Does anybody know this?

Thanks.

-- 
Yasushi Oshima