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

[Philippe Mathieu-Daudé]

On 6/9/20 7:38 AM, Markus Armbruster wrote:
> Philippe Mathieu-Daudé <f4bug@amsat.org> writes:
> 
>> 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()?
> 
> Because then aux_init_bus() is no longer "init", but "init and realize".
> Instead: "[PATCH v2 32/58] auxbus: New aux_bus_realize(), pairing with
> aux_bus_init()".  Okay?

It would be easier to follow having aux_bus_realize() introduced first,
then used it directly here. Anyway it is reviewed so I don't have a
problem if this patch goes as it. Thanks.

> 
>>> +
>>>      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,
>>>
> 
>