[Sound-open-firmware] can stream-box size be 0?

[Liam Girdwood]

On Wed, 2019-04-03 at 16:49 +0200, Guennadi Liakhovetski wrote:
> On Wed, Apr 03, 2019 at 03:39:02PM +0100, Liam Girdwood wrote:
> > On Wed, 2019-04-03 at 15:33 +0200, Guennadi Liakhovetski wrote:
> > > Hi,
> > > 
> > > In kernel ipc.c I see "if (sdev->stream_box.size == 0)" checks at
> > > exactly 4 locations, but all currently supported by SOF platforms set
> > > the size to 0x200. Do we need those checks or can we safely assume, that
> > > the size is never 0?
> > 
> > The size can depend on FW platform and how much space they allocate for
> > mmap()
> > stream position information. i.e. ALSA can read pipeline stream position
> > stats
> > directly from mailbox rather than via IPC.
> 
> Does that mean, that I misunderstood something? Could you point me out
> to the code, that can set that size to anything other than 0x200, as
> supplied by the firmware?
> 

This size can be anything, even 0 is valid. Look at the extended boot data sent
by the FW at boot in platform.c (e.g. src/platform/baytrail/platform.c)

Liam