Re: clipping

On 10 Jan 2003, Antonino Daplas wrote:

On Fri, 2003-01-10 at 05:24, James Simmons wrote:

quoted

quoted

So perhaps, a function something like this:

void fb_clip(struct fb_fillrect *region, struct fb_fillrect *clip);

This should not be difficult to implement, and I'll code it if everyone
agrees.

 
I thought about this. Originally I did have this function but removed it.
WHat do you think Geert?

quoted

The other option (which I don't like) is just to check the passed
fb_var_screeninfo in the put_var ioctl against the current console
window size.  But this is not foolproof as we will not be sure of the
resulting window size _after_ the fb_set_var() call.

Yuck!!! The other way is better.

Yes, I thought so too :-).

I think one scenario why we need clipping is changing bits_per_pixel,
ie, changing from 8->16 will drop your vyres by half and it's difficult
to determine this unless you do another check before the set_par(), as
Geert mentioned.  Worse still, there is little if no valid memory past
vyres but the console thinks there is.  That's where you will get a
segfault.

Whereas explicitly doing fbset -vyres 768 will not cause a segfault,
because you still have valid framebuffer memory past y=768.

That depends. On unified memory architectures or if the graphics memory is
shared by two heads, you may still corrupt someone's memory.

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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