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References: <20180709091136.28849-1-e.emanuelegiuseppe@gmail.com>
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From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <1222c915-3ece-5568-a708-9c29033fa47f@redhat.com>
Date: Wed, 18 Jul 2018 21:38:25 +0200
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Subject: Re: [Qemu-devel] [PATCH 2/7] tests/qgraph: pci-pc driver and
 interface nodes
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To: Emanuele <e.emanuelegiuseppe@gmail.com>, Stefan Hajnoczi <stefanha@gmail.com>
Cc: Laurent Vivier <lvivier@redhat.com>, =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= <f4bug@amsat.org>, qemu-devel@nongnu.org

On 11/07/2018 19:46, Emanuele wrote:
>>> +static void qpci(void)
>>> +{
>>> +    qos_node_create_interface("pci-bus");
>>> +}
>>> +
>>> +libqos_init(qpci);
>> Why does an interface need to be created?  The drivers declare which
>> interfaces they support?
>>
>> I don't think this can be used to detect typoes in the driver's
>> qos_node_produces() call since there is no explicit control over the
>> order in which libqos_init() functions are called.  So the driver may
>> call qos_node_produces() before the qos_node_create_interface() is
>> called?
> The interface is what is actually given to the test, so from there it
> can test the functions and fields regardless of which driver is actually
> implementing them.
> For example, sdhci-test uses the QSDHCI functions, and depending on the
> path the generic-sdhci or sdhci-pci functions will be used.

I think Stefan is right, if you adjust qos_node_create_interface so that
it is idempotent(*), you can make it static and call it from
qos_node_produces and qos_node_consumes.

(*) that is, fail like now if the node exists and is not an interface;
    but, succeed if the node exists and is an interface.

Thanks,

Paolo