Re: [PATCH v2 02/24] display/xlnx_dp: Fix to realize "i2c-ddc" and "aux-to-i2c-bridge"

[Philippe Mathieu-Daudé]

On 5/28/20 1:04 PM, Markus Armbruster wrote:
> xlnx_dp_init() creates these two devices, but they're never realized.
> Affects machine xlnx-zcu102.
> 
> In theory, a device becomes real only on realize.  In practice, the
> transition from unreal to real is a fuzzy one.  The work to make a
> device real can be spread between realize methods (fine),
> instance_init methods (wrong), and board code wiring up the device
> (fine as long as it effectively happens on realize).  Depending on
> what exactly is done where, a device can work even when we neglect to
> realize it.
> 
> These two appear to work.  Nevertheless, it's a clear misuse of the
> interface.  Even when it works today (more or less by chance), it can
> break tomorrow.
> 
> Fix by realizing them in xlnx_dp_realize().
> 
> Fixes: 58ac482a66de09a7590f705e53fc6a3fb8a055e8
> Cc: KONRAD Frederic <fred.konrad@greensocs.com>
> Cc: Alistair Francis <alistair@alistair23.me>
> Cc: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
> Cc: Peter Maydell <peter.maydell@linaro.org>
> Cc: qemu-arm@nongnu.org
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
> ---
>  hw/display/xlnx_dp.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/display/xlnx_dp.c b/hw/display/xlnx_dp.c
> index 3e5fb44e06..bdc229a51e 100644
> --- a/hw/display/xlnx_dp.c
> +++ b/hw/display/xlnx_dp.c
> @@ -1264,9 +1264,13 @@ static void xlnx_dp_realize(DeviceState *dev, Error 
> **errp)
>      DisplaySurface *surface;
>      struct audsettings as;
>  
> +    qdev_init_nofail(DEVICE(s->aux_bus->bridge));

Eh??? Why not realize the bridge in aux_init_bus()?

> +
>      qdev_init_nofail(DEVICE(s->dpcd));
>      aux_map_slave(AUX_SLAVE(s->dpcd), 0x0000);
>  
> +    qdev_init_nofail(DEVICE(s->edid));

This one is OK.

> +
>      s->console = graphic_console_init(dev, 0, &xlnx_dp_gfx_ops, s);
>      surface = qemu_console_surface(s->console);
>      xlnx_dpdma_set_host_data_location(s->dpdma, DP_GRAPHIC_DMA_CHANNEL,
>