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Date:   Fri, 11 Jun 2021 18:30:19 +0100
From:   Cristian Marussi <cristian.marussi@arm.com>
To:     Etienne Carriere <etienne.carriere@linaro.org>
Cc:     linux-kernel@vger.kernel.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: [PATCH v2 4/4] firmware: arm_scmi: add optee transport
Message-ID: <20210611173019.GB35183@e120937-lin>
References: <20210521134055.24271-1-etienne.carriere@linaro.org>
 <20210521134055.24271-4-etienne.carriere@linaro.org>
 <20210527151118.GV28060@e120937-lin>
 <CAN5uoS_0SMndmAvTwZnsCeQSUAfvBRz1diU_94CSYrsBxsZeew@mail.gmail.com>
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Hi Etienne,

On Fri, May 28, 2021 at 11:43:24AM +0200, Etienne Carriere wrote:
> Hello Christian,
> 
> On Thu, 27 May 2021 at 17:11, Cristian Marussi <cristian.marussi@arm.com> wrote:
> >
> > Hi Etienne,
> >
> > some remarks below.
> >
> > On Fri, May 21, 2021 at 03:40:54PM +0200, Etienne Carriere wrote:
> > > Add a new transport channel to the SCMI firmware interface driver for
> > > SCMI message exchange based on OP-TEE transport channel that leverage
> > > OP-TEE secure threaded context for processing of SCMI messages.
> > >
> > > +static int __init optee_scmi_init(void)

[snip]

> > > +{
> > > +     return driver_register(&optee_scmi_driver.driver);
> > > +}
> > > +
> > > +static void __exit optee_scmi_exit(void)
> > > +{
> > > +     driver_unregister(&optee_scmi_driver.driver);
> > > +}
> > > +
> > > +module_init(optee_scmi_init);
> > > +module_exit(optee_scmi_exit);
> > > +
> >
> > This cannot compile is the full SCMI statck ARM_SCMI_PROTOCOL is configured as =m
> >
> > /opt/toolchains/gcc-arm-8.3-2019.03-x86_64-aarch64-linux-gnu/bin/aarch64-linux-gnu-ld:
> > drivers/firmware/arm_scmi/optee_service.o: in function
> > `optee_scmi_init':
> > /home/crimar01/ARM/dev/src/pdsw/linux/drivers/firmware/arm_scmi/optee_service.c:515:
> > multiple definition of `init_module';
> > drivers/firmware/arm_scmi/driver.o:/home/crimar01/ARM/dev/src/pdsw/linux/drivers/firmware/arm_scmi/driver.c:1593:
> > first defined here
> > /opt/toolchains/gcc-arm-8.3-2019.03-x86_64-aarch64-linux-gnu/bin/aarch64-linux-gnu-ld:
> > drivers/firmware/arm_scmi/optee_service.o: in function
> > `optee_scmi_exit':
> > /home/crimar01/ARM/dev/src/pdsw/linux/drivers/firmware/arm_scmi/optee_service.c:520:
> > multiple definition of `cleanup_module';
> > drivers/firmware/arm_scmi/driver.o:/home/crimar01/ARM/dev/src/pdsw/linux/drivers/firmware/arm_scmi/driver.c:1611:
> > first defined here
> > /home/crimar01/ARM/dev/src/pdsw/linux/scripts/Makefile.build:449: recipe
> > for target 'drivers/firmware/arm_scmi/scmi-module.o' failed
> > make[4]: *** [drivers/firmware/arm_scmi/scmi-module.o] Error 1
> >
> >
> > Indeed it was the same issue we faced in the virtio-scmi series, and it
> > derives from the fact that SCMI transports 'driver' are really NOT
> > standalone drivers but only extension of the main SCMI module, so you
> > cannot have them initialize their stuff using usual kernel module_ machinery.
> >
> > In order to address this, and avoid a hell of ifdeffery probably,
> > in the context of virtio-scmi, I added a couple of transport's
> > optionalily provided init/deinit functions so that a transport can provide
> > some specific init code and be assured they are called at SCMI stack init,
> > so definitely even before the SCMI stack is probed and the selected
> > transport used.
> >
> > This is the patch from the virtio-scmi series:
> >
> > https://lore.kernel.org/linux-arm-kernel/20210511002040.802226-3-peter.hilber@opensynergy.com/
> >
> > which in that context is used like:
> >
> > +static int __init virtio_scmi_init(void)
> > +{
> > +       return register_virtio_driver(&virtio_scmi_driver);
> > +}
> > +
> > +static void __exit virtio_scmi_exit(void)
> > +{
> > +       unregister_virtio_driver(&virtio_scmi_driver);
> > +}
> > +
> > +const struct scmi_desc scmi_virtio_desc = {
> > +       .init = virtio_scmi_init,
> > +       .exit = virtio_scmi_exit,
> > +       .ops = &scmi_virtio_ops,
> >
> > I'll cleanup further that init/deinit patch and move it out into that bunch
> > of SCMI core changes that I'm making (in a separate series) to aid in virtio-scmi
> > devel.
> > In the meantime for your testing the above lore patch should work fine.
> 
> Thanks for the details, i'll upgrade to the series.
> 

Just a heads up that I have minimally updated this patch about transport
init/exit helpers in V4 VirtIO SCMI series, to address some bug at unloading
time I spotted while testing (even though you're not probably interested in
such load/unload scenario)

Updated patch:

https://lore.kernel.org/linux-arm-kernel/20210611165937.701-4-cristian.marussi@arm.com/T/#u

Thanks,
Cristian