Re: [PATCH 28/47] target-info: add target_config_dpcd

[Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>]

On 8/31/2026 12:04 AM, Philippe Mathieu-Daudé wrote:
> On 29/8/26 00:58, Pierrick Bouvier wrote:
> 
> No commit description explaining why we need this change.
>

See next commit in series using this.

> Guessing, XLNX_ZYNQMP_ARM is AARCH64 specific and is the single
> Kconfig selecting DPCD:
> 
>   $ qemu-system-aarch64 -device help|fgrep -i dpcd
>   name "dpcd", bus aux-bus
> 
> We want to keep '-device help' output unchanged, thus we add a
> TargetInfo dpcd field. This however doesn't sound right to handle
> a target device config in a distinct way.
> 
> IIUC the DPCD device is plugged on a AUX bus, but the wiring is
> done explicitly calling aux_map_slave(), meaning so far devices
> can not be plugged from the command line interface (maybe they
> could, but the code required to do that is not in the repository).
> IOW we shouldn't allow TYPE_AUX_BUS children to be user creatable:
> 
> -- >8 --
> diff --git a/hw/misc/auxbus.c b/hw/misc/auxbus.c
> index 877f3456062..240447598ad 100644
> --- a/hw/misc/auxbus.c
> +++ b/hw/misc/auxbus.c
> @@ -317,6 +317,7 @@ static void aux_slave_class_init(ObjectClass *klass,
> const void *data)
> 
>      set_bit(DEVICE_CATEGORY_MISC, k->categories);
>      k->bus_type = TYPE_AUX_BUS;
> +    k->user_creatable = false; /* Must be wired calling aux_map_slave() */
>  }
> 
> ---
> 
> My suggestion is to simply add a previous hunk as a patch before your
> "single-binary: command line reference" patch in this series (can send
> if you want), and not add the TargetInfo::config_dpcd field at all.
> 
>> Signed-off-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>
>> ---
>>   include/qemu/target-info-impl.h | 2 ++
>>   include/qemu/target-info.h      | 7 +++++++
>>   target-info-def.c               | 3 +++
>>   target-info.c                   | 5 +++++
>>   4 files changed, 17 insertions(+)
>>
>> diff --git a/include/qemu/target-info-impl.h b/include/qemu/target-
>> info-impl.h
>> index 4f6c898c707..045799a771a 100644
>> --- a/include/qemu/target-info-impl.h
>> +++ b/include/qemu/target-info-impl.h
>> @@ -31,6 +31,8 @@ typedef struct TargetInfo {
>>       /* runtime equivalent of TARGET_PAGE_BITS_VARY definition */
>>       bool page_bits_vary;
>>   +    /* CONFIG_DPCD */
>> +    bool config_dpcd;
>>       /* CONFIG_MULTIPROCESS */
>>       bool config_multiprocess;
>>       /* CONFIG_NITRO */
>> diff --git a/include/qemu/target-info.h b/include/qemu/target-info.h
>> index d775c94d1e3..a60751a4ef6 100644
>> --- a/include/qemu/target-info.h
>> +++ b/include/qemu/target-info.h
>> @@ -42,6 +42,13 @@ const char *target_cpu_type(void);
>>    */
>>   bool target_big_endian(void);
>>   +/**
>> + * target_config_dpcd:
>> + *
>> + * Returns true if target defines CONFIG_DPCD.
>> + */
>> +bool target_config_dpcd(void);
>