linux-kernel - Re: permission to move definition of struct rpmsg_channel

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Date:	Mon, 9 Sep 2013 22:06:24 +0200
From:	Ohad Ben-Cohen <ohad@...ery.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Arjun Gopalan <agopalan@...dia.com>,
	Brian Swetland <swetland@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Paul Walmsley <pwalmsley@...dia.com>
Subject: Re: permission to move definition of struct rpmsg_channel_info

On Mon, Sep 9, 2013 at 2:57 PM, Thierry Reding <thierry.reding@...il.com> wrote:
> If I understand correctly, the way that the services should be announced
> is via RSC_VDEV entries in the resource table?

Yes.

> Looking at the remoteproc core and ELF loader, it seems like the way to
> pass in the resource table is either via an extra ELF section or driver
> specific. TI drivers seem to use ELF, but the STE modem driver seems to
> employ some custom format.
>
> From what I understand this resource table can also be processed by the
> host to provide some of the resources such as carveout memory. So that
> the normal way for this to work would be something like:
>
>         - load firmware image
>           - obtain pointer to resource table
>         - process resource table
>           - allocate resources
>           - update table
>         - upload firmware to remote processor
>
> Upon which the remote processor probably needs to parse the resource
> table to set itself up. Does that sound about right?

Yeah, it generally does.

> > The way we were planning to add static channels functionality (I
> > should still have preliminary patches doing this somewhere but the
> > entire work was put on hold since TI changed its focus) is by
> > statically publishing them in the resource table, which is coupled
> > with a specific remote image.
>
> While I see that the format of all this is pretty well documented, are
> there any standard tools that can be used to embed the resource table
> into an ELF binary?

I'm not aware of any.

> I have a pretty good idea on how it could be done,
> but I wonder if it might make sense to provide some kind of a standard
> set of headers to make things easier so that not everyone has to
> reinvent the wheel.
>
> Looking at the remoteproc core, it seems that there's no direct way to
> change the firmware running on a remoteproc at runtime.

One way is to unload and load the driver, but you can also use the
bind/unbind sysfs files of your driver (echo -n device-name >
/sys/..../{un}bind).

Does that help?

Best,
Ohad.
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