Re: [Qemu-arm] [RFC PATCH 0/6] qom: introduce TypeInfo name aliases

[Philippe Mathieu-Daudé]

Hi Igor,

On 01/08/2018 09:51 AM, Igor Mammedov wrote:
[...]
> Though it seems easy and trivial, I'm a bit concerned about using
> QOM types for the task though.
> Also see commit 6acbe4c6f which labels aliases as a bad idea
> and says that they are there only for compatibility and shouldn't
> be used.
> So far I agree with that statement, because it introduces
> ambiguity in code used internally and more worrying is that
> this ambiguity will increase user visible ABI (think of '-device_add 
> FOO_ALIAS')
> that we would need to maintain afterwards.
> It would be nice to have unified alias API, but I think it should
> be separate one and limited to the same scope (i.e. compat stuff),
> and even that won't be easy as different alias impl. we have now
> have a different needs.
> 
> wrt this series targeted usage, I'd prefer that object_new/initialize
> would use real type names when creating devices as it does currently
> 
> FDT linux guest specific names wouldn't seep into device model
> itself. Firmware (FDT or ACPI) should be separate from device
> implementation.

Good point.

> If really there is need to dynamically scan present devices
> and build FDT from result, then probably we should introduce
> interface that devices could implement if necessary.
> (I was thinking about such possibility for ACPI). But so far
> it looked to me as too much overhead for what we do now.

I see, I thought about something similar but TypeInfo.aliases was way
too simple to not try this series first.

What about adding a INTERFACE_FDT_DEVICE type (InterfaceInfo) and let
the FDT devices implement something such:

typedef struct {
    /*< private >*/
    InterfaceClass parent_class;
    DeviceClass parent_class;
    /*< public >*/
    bool (*is_alias)(FDTDeviceIf *dev, const char *name);
    bool (*set_prop...)(FDTDeviceIf *dev, const char *property, ...);
    const void *(*get_prop)(FDTDeviceIf *dev, const char *property);
};

Regards,

Phil.

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