Re: [Qemu-devel] [PATCH] ati-vga: Implement DDC and EDID info from monitor

[Gerd Hoffmann]

On Sun, Mar 10, 2019 at 12:22:17AM +0100, BALATON Zoltan wrote:
> This adds DDC support to ati-vga and connects i2c-ddc to provide EDID
> info that is read by guests to find available screen modes. Not sure
> if this is 100% correct yet but at least MorphOS is happy with it and
> starts in a high resolution mode instead of 640x480 (although its
> splash screen is still not correct).

> Linux needs support from VESA
> vgabios, it seems to be missing INT10 0x4F15 function (see
> https://gitlab.freedesktop.org/xorg/xserver/blob/master/hw/xfree86/vbe/vbe.c)
> without which no DDC is available that also prevents loading the
> accelerated X driver.

radeonfb doesn't pick up the edid either.
There seem to be four i2c busses though:

void radeon_create_i2c_busses(struct radeonfb_info *rinfo)
{
        rinfo->i2c[0].rinfo     = rinfo;
        rinfo->i2c[0].ddc_reg   = GPIO_MONID;
#ifndef CONFIG_PPC
        rinfo->i2c[0].adapter.class = I2C_CLASS_HWMON;
#endif
        radeon_setup_i2c_bus(&rinfo->i2c[0], "monid");

        rinfo->i2c[1].rinfo     = rinfo;
        rinfo->i2c[1].ddc_reg   = GPIO_DVI_DDC;
        radeon_setup_i2c_bus(&rinfo->i2c[1], "dvi");

        rinfo->i2c[2].rinfo     = rinfo;
        rinfo->i2c[2].ddc_reg   = GPIO_VGA_DDC;
        radeon_setup_i2c_bus(&rinfo->i2c[2], "vga");

        rinfo->i2c[3].rinfo     = rinfo;
        rinfo->i2c[3].ddc_reg   = GPIO_CRT2_DDC;
        radeon_setup_i2c_bus(&rinfo->i2c[3], "crt2");
}

aty128fb has no i2c support.

> Besides, this depends on bitbang_i2c.h which is now in hw/i2c so if
> including it from there is not desirable that may need to be moved
> somewhere.

include/hw/i2c/ looks like a sensible location to me.

cheers,
  Gerd