edid_info is already a pointer.

Should be:
    if (memcmp(edid_info, magic, sizeof (magic)) != 0)

or
    if (memcmp(edid_info->header.header, magic, sizeof (magic)) != 0)

Ship It!

Ship it!
I'm thinking about a little further enhancement, to improve code readability and consistency:

Helper macros for handling detailed_timings through vesa_edid_info:

/usr/src/boot/sys/boot/common/gfx_fb.h:

#define GET_EDID_INFO_WIDTH(edid_info, timings_num) \
    ((edid_info).detailed_timings[(timings_num)].horizontal_active_lo | \
    (((uint_t)(edid_info).detailed_timings[(timings_num)].horizontal_hi & \
    0xf0) << 4))

#define GET_EDID_INFO_HEIGHT(edid_info, timings_num) \
    ((edid_info).detailed_timings[(timings_num)].vertical_active_lo | \
    (((uint_t)(edid_info)->detailed_timings[(timings_num)].vertical_hi & \
    0xf0) << 4))


/usr/src/boot/sys/boot/i386/libi386/vbe.c:
static bool
vbe_get_edid(uint_t *pwidth, uint_t *pheight)
{
    struct vesa_edid_info *edid_info;
    const uint8_t magic[] = EDID_MAGIC;
    int ddc_caps;
    bool ret = false;

    ddc_caps = biosvbe_ddc_caps();
    if (ddc_caps == 0) {
        return (ret);
    }

    edid_info = bio_alloc(sizeof (*edid_info));
    if (edid_info == NULL)
        return (ret);

    if (VBE_ERROR(biosvbe_ddc_read_edid(0, edid_info)))
        goto done;

    if (memcmp(edid_info, magic, sizeof (magic)) != 0)
        goto done;

    if (!(edid_info->header.version == 1 &&
        (edid_info->display.supported_features
        & EDID_FEATURE_PREFERRED_TIMING_MODE) &&
        edid_info->detailed_timings[0].pixel_clock))
        goto done;

    *pwidth = GET_EDID_INFO_WIDTH(edid_info, 0);
    *pheight = GET_EDID_INFO_HEIGHT(edid_info, 0);

    ret = true;
done:
    bio_free(edid_info, sizeof (*edid_info));
    return (ret);
}



*timings variable removed + consistently using cast (uint_t used in the macro instead of int):

/usr/src/boot/sys/boot/efi/loader/framebuffer.c:

static int
efifb_get_edid(UINT32 *pwidth, UINT32 *pheight)
{
    extern EFI_GRAPHICS_OUTPUT *gop;
    struct vesa_edid_info *edid_info;
    int rv = 1;

    edid_info = efifb_gop_get_edid(gop);
    if (edid_info != NULL) {
        *pwidth = GET_EDID_INFO_WIDTH(edid_info, 0);
        *pheight = GET_EDID_INFO_HEIGHT(edid_info, 0);
        rv = 0;
    }
    free(edid_info);
    return (rv);
}


What are the opinions about this?

Ship It!