[Sound-open-firmware] How do you provide the firmware binary, e.g sof-byt.ri file?

[Takashi Iwai]

On Mon, 10 Dec 2018 16:00:10 +0100,
Liam Girdwood wrote:
> 
> On Mon, 2018-12-10 at 07:48 -0600, Pierre-Louis Bossart wrote:
> > > I am having this problem where SOF is compiled as built in the
> > > kernel and the firmware binary is on the rootfs.
> > > 
> > > When request_firmware is called in sof_probe the rootfs
> > > is not yet mounted so the call to request_firmware fails.
> > > 
> > > Just curious, how do you provide the firmware binary?
> > 
> > it's a known issue that we haven't fixed since we use modules both for 
> > development and production. Other drivers have the same problem IIRC.
> > 
> 
> You could try adding the image to initramfs, but as Pierre says this is a
> general problem with loading FW on Linux, not just related to audio.

Right, it's a PITA for drivers.

The driver can use request_firmware() for simplicity, but it's a
synchronous API, hence the firmware has to be present statically in
the kernel image if the driver is built-in.
OTOH, request_firmware_nowait() would work asynchronously and you can
delay the load for another rootfs mount, but it's often difficult to
design / code correctly.


Takashi