Re: [PATCH v8 3/4] gpio: rpmsg: add generic rpmsg GPIO driver

[Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>]

On 2/19/26 14:42, Andrew Lunn wrote:
>>> +	u8 id;		/* Message ID Code */
>>> +	u8 vendor;	/* Vendor ID number */
>>
>> Does this fields above are mandatory, seems that it is just some constant
>> values that are useless.
>>
>>> +	u8 version;	/* Vendor-specific version number */
>>
>> Why it is vendor specific? the version should represent the rpmsg-tty
>> protocol version.
>>
>>> +	u8 type;	/* Message type */
>>> +	u8 cmd;		/* Command code */
>>> +	u8 reserved[5];
>>
>> What is the purpose of this reserved field?
> 
> They have an implementation of the other end running on there systems,
> and it sounds like it is widely deployed, and they are trying to keep
> backwards compatibility. The protocol also implements more than
> GPIO. There is also I2C, maybe watchdog, i don't remember, but early
> versions of this patchset had a list. Some of these fields are used
> for some of these other devices.
> 
> I've been arguing it should be a clean design, with the protocol
> focusing on GPIO. And that the rpmsg channel makes it clear this is a
> GPIO device, the protocol itself does not need to include fields to
> differentiate between GPIO, I2C etc.
> 
> When they start submitting I2C over rpmsg, i expect the same sort of
> discussion will start again, so the likelihood of keeping backwards
> compatible with there firmware seems low to me.

Agree with you.

Thanks,
Arnaud

> 
> 	   Andrew