Re: [PATCH 9/9] edid: add support for DisplayID extension (5k resolution)

[Philippe Mathieu-Daudé]

On 3/16/21 3:38 PM, Gerd Hoffmann wrote:
> From: Konstantin Nazarov <mail@knazarov.com>
> 
> The Detailed Timing Descriptor has only 12 bits to store the
> resolution. This limits the guest to 4095 pixels.
> 
> This patch adds support for the DisplayID extension, that has 2 full
> bytes for that purpose, thus allowing 5k resolutions and above.
> 
> Based-on: <20210303152948.59943-2-akihiko.odaki@gmail.com>
> Signed-off-by: Konstantin Nazarov <mail@knazarov.com>
> Message-Id: <20210315114639.91953-3-mail@knazarov.com>
> 
> [ kraxel: minor workflow tweaks ]
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  hw/display/edid-generate.c | 78 +++++++++++++++++++++++++++++++++++---
>  hw/display/vga-pci.c       |  2 +-
>  2 files changed, 74 insertions(+), 6 deletions(-)

> +static void qemu_displayid_generate(uint8_t *did, uint32_t refresh_rate,
> +                                    uint32_t xres, uint32_t yres,
> +                                    uint32_t xmm, uint32_t ymm)
> +{
> +    Timings timings;
> +    generate_timings(&timings, refresh_rate, xres, yres);
> +
> +    did[0] = 0x70; /* display id extension */
> +    did[1] = 0x13; /* version 1.3 */
> +    did[2] = 23;   /* length */
> +    did[3] = 0x03; /* product type (0x03 == standalone display device) */
> +
> +    did[5] = 0x03; /* Detailed Timings Data Block */
> +    did[6] = 0x00; /* revision */
> +    did[7] = 0x14; /* block length */
> +
> +    did[8]  = timings.clock  & 0xff;
> +    did[9]  = (timings.clock & 0xff00) >> 8;
> +    did[10] = (timings.clock & 0xff0000) >> 16;
> +
> +    did[11] = 0x88; /* leave aspect ratio undefined */
> +
> +    stw_le_p(did + 12, 0xffff & (xres - 1));
> +    stw_le_p(did + 14, 0xffff & (timings.xblank - 1));
> +    stw_le_p(did + 16, 0xffff & (timings.xfront - 1));
> +    stw_le_p(did + 18, 0xffff & (timings.xsync - 1));
> +
> +    stw_le_p(did + 20, 0xffff & (yres - 1));
> +    stw_le_p(did + 22, 0xffff & (timings.yblank - 1));
> +    stw_le_p(did + 24, 0xffff & (timings.yfront - 1));
> +    stw_le_p(did + 26, 0xffff & (timings.ysync - 1));

Pointless 0xffff mask.

> +
> +    edid_checksum(did + 1, did[2] + 4);
> +}