On Fri, 29 Aug 2008, Takashi Yoshii wrote:

Thank you for your explanation.
Sorry for slow, long response.
Summary:
1. I understand your strategy (no check == fix video).
2. pan should be fixed state after set var.
3. pixclock can be any, OK?

---
1. 

quoted

quoted

If the driver doesn't provide a fb_check_var(), it means it cannot
change video mode. Hence this rules out #1.

Well, this logic looks like "A is B because A is B".
But, anyway this should be this because you say so.
Accepting this as a fixed rule, things becomes simple.

I guess this is based on the idea
var should always be corresponding to HW state.
My patch was based on the idea
var can be any, because HW accept all (by just ignoring all).

No, var cannot be any. Var can only be the single tuple of values the
hardware supports.

2. pan should be fixed state after set var.

# This is becoming another topic, though...
One small problem of current code is that
FBIOPUT_VSCREENINFO sometimes set PAN but sometimes does not.
# assuming pan is not a part of "video mode".

It will be 1.unchanged, or 2.info->var, or 3.var, or 4.var+rounding?,
but generally pan state after FBIOPUT_VSCREENINFO should be considered
as unknown(but something valid), even if passing valid value(say, (0,0)).

Panning state is not unknown. It's in var.

3. pixclock can be any, OK?

The real problem(for me;) might be
. Habit of applications that check the var by themselves.
This is  not actually a topic on this ML. But I want to confirm that
 pixclock can be any. Even 0 is a kind of "Valid" value.
OK?

I'm asking because, there are drivers return timing parameters as 0.
- HW has clock, known, but set 0 (sh_mobile_lcdfb).
- HW must have clock, but unknown (hitfb, stifb, xilinxfb).
- No clock (xenfb).
There are drivers return false value.
- No clock but return some (vfb).

If 0 is valid, problem is Xorg's issue.
X(at least 1.4) doesn't accept clock=0. (and the reason looks be buggy)

If you don't know the pixclock, set it to 0.

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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