Re: st_fdma: Firmware filename in DT?

On Fri, Sep 4, 2015 at 9:27 AM, Warner Losh [off-list ref] wrote:

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On Sep 4, 2015, at 4:21 AM, Lee Jones [off-list ref] wrote:

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We could do it by parsing the node name e.g. fdma0-audio, or by adding
a "instance" DT property to the node?

Generally we try to avoid caring about node names. Having some index
or numbering also comes up which we also try to avoid. Generally, if
you care about which instance you use for something, then there is
some property you care about and should add.

Right, the alternative is a property like the ones already used.
However, as these are becoming more prevalent I suggested
standardising the property to avoid all these vendor specific firmware
properties cluttering up the place.

I agree a proliferation of vendor specific firmware properties isn't
s good way forward.

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 firmware = "firmwarename.fw";
OR
 firmware-name = "firmwarename.fw";

... seems appropriate.

Either of those is fine with me.

Just need a DT nod and I'll happily code it up.

From a FreeBSD perspective, having a filename for the firmware to
load for this node is fine. It doesn’t impose a substantial burden on
the OS so long as the choices of where that file lives is up to the OS
and not encoded in the property. A note saying ‘this firmware should
be loaded’ seems a reasonable description of the hardware since
the DT tells us many things about the device, and those things may
well be dependent on which firmware is loaded. Having an explicit
name is good since it helps insulate from DT and doesn’t force vendors
to do silly renames. It also allows for multiple devices of the same
type to have different firmware loaded.

FreeBSD would generally put these things in /boot/firmware and
it has a generalized mechanism to load the firmware at run time
that’s based on this. While the path names are flexible, having
the firmware live in a central place is useful from an automation
point of view. Having just a name, and not a full path, enables
this policy, while still allowing others to have other policies.

Linux distributions would be free to do whatever they wanted
and implement other policies than FreeBSD.

So a property like this, with the semantics discussed, seems to
meet the OS independent test.

Good. I'll await a binding to review...

I would suggest "firmware-names" to be consistent with other naming
convention and because their can be more than one (either at the same
time or as fallback). It also leaves "firmware" available if we want
to have phandle's to firmware embedded in the DT at some point later.

Rob