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

[Markus Armbruster]

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?

>> +
>>      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,
>>