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

On Mon, May 24, 2021 at 07:20:45PM -0700, Florian Fainelli wrote:

On 5/24/2021 4:15 PM, Cristian Marussi wrote:

quoted

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@arm.com>

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

I agree, definitely better to see this in the context of usage.

Such virtio-scmi rework is still in progress indeed, but working in my
local testing so far.

The reworked V4 virtio-scmi series is still to be refined and posted,
and this transitional code lives now at:

https://gitlab.arm.com/linux-arm/linux-cm/-/tree/scmi_virtio_trans_V4_rework

and in particular this is the patch that changes virtio-scmi transport to
use the new delegated xfers. (hopefully simplfying it)

https://gitlab.arm.com/linux-arm/linux-cm/-/commit/0b524f89ea6cfcf6204a5eaa8cf9030118805b2f

...but, as said, it is highly work in progress so you may just want to
wait for final V4 virtio-scmi rework posted and do not bother this noise
of mine :D

In any case thanks a lot for the feedback so far.

Cristian

-- 
Florian

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