Re: [PATCH] updated vfb.c

[Geert Uytterhoeven]

On Wed, 9 Feb 2000, James Simmons wrote:
>    I updated the patch again. Its against a 2.3.43-4 kernel. It compiles
> but I need to solve one more issue before I offically release it. That is
> I use vmalloc which allocates virtual memory for the driver. What I want
> to do is allocate a chunk of physical memory.  I could use kmalloc but I'm
> limited to 128K of memory. I could use bootmem but that seems to be good
> only at boot time thus it couldn't be a module. Am I wrong here? I need

I think kmalloc() is the best thing for vgb. Vfb is just meant to be a sample
driver, so the limitation to 128 KB is not that important. It's more important
that you can actually mmap() it from user space, which is not possible with
vmalloc().

> to also show a good example of the use of par. All fbdev driver writers

I'm afraid there's not much `par' to show in vfb, unless you invent some fake
registers that have to be set up... Hmm, why not do that?

Another thing: to avoid flicker and to avoid expensive PCI bus accesses, it can
be useful to check whether you really have to write a register value. If your
`par' looks sufficiently like the real hardware registers, you can define

    static inline __set_reg(unsigned long reg, u32 val, u32 *oldval)
    {
	if (val != *oldval) {
	    real_set_reg(reg, val);
	    *oldval = val);
	}
    }
    #define set_reg(reg, val)	__set_reg(reg, par->val, &oldpar->val)

and use

    oldpar = fb_info->par;
    set_reg(REG_XX1, reg_xx1);
    set_reg(REG_XX2, reg_xx2);
    set_reg(REG_XX3, reg_xx3);
    set_reg(REG_XX4, reg_xx4);

This is also useful for accel engine setup for accelerated rectcopy/rectfill.

> please read the text in vfb.c after appling the patch. It represents the
> ideas where fbcon is heading in terms of future API. Please take advantage
> of the var and fix fields inside fb_info. This patch also adds a fbcmap
> field to fb_info.

OK.

Gr{oetje,eeting}s,
--
Geert Uytterhoeven -- Linux/{m68k~Amiga,PPC~CHRP} -- [e-mail]

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