[9fans] quick stupid question

[9fans] quick stupid question

[Roman Shaposhnick]

Guys,

its a bit embarrassing, but I can't really find a place in
the sources where vgascreen (the one defined in 9/pc/screen.h)
gets initialized :-( I've grepped and grepped, but I only
see its usage everywhere...

Help, please...

Thanks,
Roman.

Re: [9fans] quick stupid question

[geoff]

It looks like it's initialised in 9/pc/screen.c, for example in
screensize(), and 9/pc/devvga.c, for example in vgaopen() and the
routines it calls.  Look for

	scr = &vgascreen[0];

which is a pedantic way of writing

	scr = vgascreen;

and see how scr is used.

Re: [9fans] quick stupid question

[Roman Shaposhnick]

On Mon, Jun 05, 2006 at 06:24:31PM -0700, geoff@collyer.net wrote:
> It looks like it's initialised in 9/pc/screen.c, for example in
> screensize(), and 9/pc/devvga.c, for example in vgaopen() and the
> routines it calls.  Look for
> 
> 	scr = &vgascreen[0];
> 
> which is a pedantic way of writing
> 
> 	scr = vgascreen;
> 
> and see how scr is used.

  Here's the thing -- it looks like everything assumes that the place
  'scr' ends up pointing to has been already initialized somehow. Every 
  sourceline that I've been able to identify using 
      "grep vgascreen  /sys/src/9/*/*" 
  does exactly what you've mentioned: 'scr = &vgascreen[0];' but the problem 
  is -- scr never gets written to, which means there's not way vgascreen could 
  be initialized. 
  
  Or am I missing something really obvious here ?

Thanks,
Roman.

Re: [9fans] quick stupid question

[Roman Shaposhnick]

On Mon, Jun 05, 2006 at 07:41:53PM -0700, Russ Cox wrote:
> >   does exactly what you've mentioned: 'scr = &vgascreen[0];' but the problem 
> >   is -- scr never gets written to, which means there's not way vgascreen could 
> >   be initialized. 
> 
> grep 'scr->[a-z]+ =' /sys/src/9/pc/*.c
> screen.c, devvga.c, also various vga*.c.

  Oh my! Thanks -- hopefully my current onset of stupidity will
  pass with a good night's sleep...

Thanks,
Roman.

Re: [9fans] quick stupid question

[Russ Cox]

> 	scr = &vgascreen[0];
> 
> which is a pedantic way of writing
> 
> 	scr = vgascreen;

Except that the former conveys the fact that
there might be more than one screen (at some point...).

Russ

Re: [9fans] quick stupid question

[Russ Cox]

>   does exactly what you've mentioned: 'scr = &vgascreen[0];' but the problem 
>   is -- scr never gets written to, which means there's not way vgascreen could 
>   be initialized. 

grep 'scr->[a-z]+ =' /sys/src/9/pc/*.c
screen.c, devvga.c, also various vga*.c.

russ