Re: Re: [RFC] Video Mode Handling

On Mon, 9 Aug 2004, Andrew Morton wrote:

Geert Uytterhoeven [off-list ref] wrote:

quoted

On Sun, 8 Aug 2004, Andrew Morton wrote:

quoted

"Antonino A. Daplas" [off-list ref] wrote:

quoted

Most fbdev developers are proposing to bring back the per-display var
 structures to ease the difficulty of video mode handling.  This proposal
 is countered by a few (notably James) in that it severely increases the
 memory footprint of the kernel.

Surprised.

By how much does this increase the kernel's memory footprint?

Indeed, you need a full mode database per driver.

Sorry, that's way outside my area of knowledge ;)

Each driver needs a list of supported video modes.

quoted

quoted

And how much simpler would the code be if we were to bring back the
per-display var structures?

IOW: what's the tradeoff here?

  - per-display var:
      - increase memory footprint by
        MAX_NR_CONSOLES.*sizeof(struct var_screen_info)

I see no var_screen_info.  sizeof(struct screen_info) is 56 bytes, and
there are 63 of them.  This is a negligible amount of memory!

Sorry, struct fb_var_screeninfo.

quoted

      + simpler code
      + 100% compatible with 2.4

  - private modedb:
      - increase memory footprint by full mode database per driver.
      - more complex (and larger) code
      - subtle differences with 2.4, because not the whole var is saved
        (BTW, which fields do you want to save, and which not, so I can
	 evaluate the impact on some drivers?)

Well gee.  If we're talking about 3k, or even 10k or 30k, let's go with the
simplest code?

I agree!

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds


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