linux-kernel - Re: [PATCH v4 02/37] firmware: arm_scmi: introduce protocol handle definitions

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Message-ID: <3b688bdf-46c4-5263-66c9-60f9b3b26588@linaro.org>
Date:   Fri, 8 Jan 2021 10:50:46 -0500
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Cristian Marussi <cristian.marussi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        sudeep.holla@....com, lukasz.luba@....com,
        james.quinlan@...adcom.com, Jonathan.Cameron@...wei.com,
        f.fainelli@...il.com, etienne.carriere@...aro.org,
        vincent.guittot@...aro.org, souvik.chakravarty@....com
Subject: Re: [PATCH v4 02/37] firmware: arm_scmi: introduce protocol handle
 definitions



On 1/8/21 7:04 AM, Cristian Marussi wrote:
> Hi Thara
> 
> thanks for reviewing.
> 
> On Thu, Jan 07, 2021 at 09:29:17AM -0500, Thara Gopinath wrote:
>>
>>
>> On 1/6/21 3:15 PM, Cristian Marussi wrote:
>>> Add basic protocol handles definitions and private data helpers support.
>>>
>>> A protocol handle identifies a protocol instance initialized against a
>>> specific handle; it embeds all the references to the core SCMI xfer methods
>>> that will be needed by a protocol implementation to build and send its own
>>> protocol specific messages using common core methods.
>>>
>>> As such, in the interface, a protocol handle will be passed down from the
>>> core to the protocol specific initialization callback at init time.
>>>
>>> Anyway at this point only definitions are introduced, all protocols
>>> initialization code and SCMI drivers probing is still based on the old
>>> interface, so no functional change.
>>>
>>> Signed-off-by: Cristian Marussi <cristian.marussi@....com>
>>> ---
>>>    drivers/firmware/arm_scmi/common.h | 59 ++++++++++++++++++++++++++++++
>>>    drivers/firmware/arm_scmi/driver.c | 45 +++++++++++++++++++++++
>>>    2 files changed, 104 insertions(+)
>>>
>>> diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
>>> index e052507dc918..977e31224efe 100644
>>> --- a/drivers/firmware/arm_scmi/common.h
>>> +++ b/drivers/firmware/arm_scmi/common.h
>>> @@ -149,6 +149,65 @@ int scmi_xfer_get_init(const struct scmi_handle *h, u8 msg_id, u8 prot_id,
>>>    		       size_t tx_size, size_t rx_size, struct scmi_xfer **p);
>>>    void scmi_reset_rx_to_maxsz(const struct scmi_handle *handle,
>>>    			    struct scmi_xfer *xfer);
>>> +
>>> +struct scmi_xfer_ops;
>>> +
>>> +/**
>>> + * struct scmi_protocol_handle  - Reference to an initialized protocol instance
>>> + *
>>> + * @dev: A reference to the associated SCMI instance device (handle->dev).
>>> + * @xops: A reference to a struct holding refs to the core xfer operations that
>>> + *	  can be used by the protocol implementation to generate SCMI messages.
>>> + * @set_priv: A method to set protocol private data for this instance.
>>> + * @get_priv: A method to get protocol private data previously set.
>>> + *
>>> + * This structure represents a protocol initialized against specific SCMI
>>> + * instance and it will be used as follows:
>>> + * - as a parameter fed from the core to the protocol initialization code so
>>> + *   that it can access the core xfer operations to build and generate SCMI
>>> + *   messages exclusively for the specific underlying protocol instance.
>>> + * - as an opaque handle fed by an SCMI driver user when it tries to access
>>> + *   this protocol through its own protocol operations.
>>> + *   In this case this handle will be returned as an opaque object together
>>> + *   with the related protocol operations when the SCMI driver tries to access
>>> + *   the protocol.
>>> + */
>>> +struct scmi_protocol_handle {
>>> +	struct device *dev;
>>> +	const struct scmi_xfer_ops *xops;
>>> +	int (*set_priv)(const struct scmi_protocol_handle *ph, void *priv);
>>> +	void *(*get_priv)(const struct scmi_protocol_handle *ph);
>>> +};
>>> +
>>> +/**
>>> + * struct scmi_xfer_ops  - References to the core SCMI xfer operations.
>>> + * @version_get: Get this version protocol.
>>> + * @xfer_get_init: Initialize one struct xfer if any xfer slot is free.
>>> + * @reset_rx_to_maxsz: Reset rx size to max transport size.
>>> + * @do_xfer: Do the SCMI transfer.
>>> + * @do_xfer_with_response: Do the SCMI transfer waiting for a response.
>>> + * @xfer_put: Free the xfer slot.
>>> + *
>>> + * Note that all this operations expect a protocol handle as first parameter;
>>> + * they then internally use it to infer the underlying protocol number: this
>>> + * way is not possible for a protocol implementation to forge messages for
>>> + * another protocol.
>>> + */
>>> +struct scmi_xfer_ops {
>>
>> Maybe move the definition above struct scmi_protocol_handle to avoid a
>> declaration ?
>>
> 
> But all the ops defined inside scmi_xfer_ops refers then to a param
> struct scmi_protocol_handle, so I'd need anyway a similar declaration
> the other way around.
> 
> If not:
> 
> linux/drivers/firmware/arm_scmi/common.h:178:32: warning: ‘struct scmi_protocol_handle’ declared inside parameter list will not be visible outside of this definition or declaration

Ya. got it. I had not realized this.
> 
> Thanks
> 
> Cristian
>>
>> -- 
>> Warm Regards
>> Thara

-- 
Warm Regards
Thara