linux-kernel - Re: [PATCH V3] firmware: arm_scmi: Make scmi core independent of the transport type

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Message-ID: <d5d71818-e68f-7688-4378-64d96bea922d@arm.com>
Date:   Thu, 23 Jan 2020 11:06:38 +0000
From:   Cristian Marussi <cristian.marussi@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     arnd@...db.de, Sudeep Holla <sudeep.holla@....com>,
        jassisinghbrar@...il.com, peng.fan@....com,
        peter.hilber@...nsynergy.com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V3] firmware: arm_scmi: Make scmi core independent of the
 transport type

On 23/01/2020 02:39, Viresh Kumar wrote:
> On 22-01-20, 12:44, Cristian Marussi wrote:
>> On 21/01/2020 08:27, Viresh Kumar wrote:
>> commment is obsolete
> 
> Right, they need to be checked everywhere again. Sorry for missing
> that earlier.
> 
>>> +struct scmi_chan_info {
>>> +	struct scmi_info *info;
>>> +	struct device *dev;
>>> +	struct scmi_handle *handle;
>>> +	void *transport_info;
>>> +};
>>> +
>>> +/**
>>> + * struct scmi_transport_ops - Structure representing a SCMI transport ops
>>> + *
>>> + * @send_message: Callback to send a message
>>> + * @mark_txdone: Callback to mark tx as done
>>> + * @chan_setup: Callback to allocate and setup a channel
>>> + * @chan_free: Callback to free a channel
>>> + */
>> commment is obsolete but I would also ask: are all of these operations supposed to be mandatory supported
>> on any possible foreseeable transport ? (beside the obviously needed like send_message)
>>
>> I'm asking because they are all called straight away from the driver core without any NULL check
>> so that if a new transport should not need one of them it will be forced to anyway implement a dummy one
>> to comply, which it will be needlessly invoked every time.
> 
> They are kept as mandatory for now as we don't really know how it
> will look for other transport types. Lets make them optional only when
> someone don't need to define them. It would be a simple change anyway.

Ok, fine.
> 
>>>  /* Each compatible listed below must have descriptor associated with it */
>>>  static const struct of_device_id scmi_of_match[] = {
>>> -	{ .compatible = "arm,scmi", .data = &scmi_generic_desc },
>>> +	{ .compatible = "arm,scmi", .data = &scmi_mailbox_desc },
>>>  	{ /* Sentinel */ },
>>>  };
>>
>> minor thing: shouldn't the chosen transport being configurable at compile time with some
>> option like CONFIG_SCMI_TRANSPORT_MBOX ? or via DT ?
> 
> It is configurable via DT. The compatible should look different in
> that case, something like: "arm,scmi-<newtranport>".
> 

Ah ok, we're assuming mailbox transport as the default, being the only one existing as of now.
Fine for me, thanks for the explanation.

Reviewed-by: Cristian Marussi <cristian.marussi@....com>

Regards

Cristian