LinuxKPI: firmware, implement deferred loading for "nowait"

[bz]

Summary

Change linuxkpi_request_firmware_nowait() to deferred firmware loading
scheduling a task. This changes behaviour in some cases that we
return from loading the driver before the driver is finished
initialising if the driver does not deal with it (wait).
This brings the behaviour one would expect from when this function is
called and I implemented it to see if it would help a specific case.

Sponsored by: The FreeBSD Foundation
MFC after: 12 days

[imp]

Looks good to my eye... it's super close to how I'd write it...

[• hselasky]

sys/compat/linuxkpi/common/src/linux_firmware.c

152

I suggest setting the "fw" to NULL here, because you pass this pointer on failure to the callback function.

164

Maybe print an error in dmesg on error. Makes it easier to locate missing firmware files.

165

Call lfwt->cont unconditionally?

[bz]

sys/compat/linuxkpi/common/src/linux_firmware.c

152

That's only an issue in case we do the call unconditionally below; otherwise it should always be initialised or we don't call "cont".

164

_linuxkpi_request_firmware dos that for you.

165

Do we need to? We didn't do before but probably given there is no other error propagation, the only alternate for a driver to know would be to "timeout"?

[bz]

Make sure *fw is initialised in all cases.
Unconditionally call the callback function as it is the only feedback path
to the requester.

[• hselasky]

You may want to wait for pending tasks at linuxkpi module unload, if the driver doesn't do that.

--HPS