[PATCH 4/4] firmware: arm_scmi: Introduce delegated xfers support

[Florian Fainelli]

On 5/24/2021 4:15 PM, Cristian Marussi wrote:
> Introduce optional support for delegated xfers allocation.
> 
> An SCMI transport can optionally declare to support delegated xfers and
> then use a few helper functions exposed by the core SCMI transport layer to
> query the core for existing in-flight transfers matching a provided message
> header or alternatively and transparently obtain a brand new xfer to handle
> a freshly received notification message.
> In both cases the obtained xfer is uniquely mapped into a specific xfer
> through the means of the message header acting as key.
> 
> In this way such a transport can properly store its own transport specific
> payload into the xfer uniquely associated to the message header before
> even calling into the core scmi_rx_callback() in the usual way, so that
> the transport specific message envelope structures can be freed early
> and there is no more need to keep track of their status till the core
> fully processes the xfer to completion or times out.
> 
> The scmi_rx_callbak() does not need to be modified to carry additional
> transport-specific ancillary data related to such message envelopes since
> an unique natural association is established between the xfer and the
> related message header.
> 
> Existing transports that do not need anything of the above will continue
> to work as before without any change.
> 
> Signed-off-by: Cristian Marussi <cristian.marussi at arm.com>

It would be better to see this in the context of its planned user, but
that looked reasonable enough.
-- 
Florian