On 8/27/19 10:08 AM, Cezary Rojewski wrote:
On 2019-08-27 17:00, Pierre-Louis Bossart wrote:
On the second thought what if instead of
duplicating kernel code, binaries would be
duplicated? I.e. rather than targeting
/intel/dsp_fw_cnl.bin, _new_ /skylake would be
expecting /intel/dsp_fw_cnl_release.bin? Same with
topology binaries. In such case, we "only" need to
figure out how to propagate new files to Linux
distos so whenever someone updates their kernel,
new binaries are already present in their
/lib/firmware.
If such option is valid, we can postpone /skylake
upgrade till 5.4 merging window closes and the
patches (rough estimation is 150) would descend
upon alsa-devel in time between 5.4 and 5.5.
If the driver and FW update will be within the same
kernel release then IMHO there should be no
compatibility problem between those two components,
right? This way kernel users willing to stick to old
FW can stay on older kernel version while others can
update and receive all the latest FW functionality
that was developed and enabled.
I am not comfortable with precluding a kernel update
because of a single firmware file. There are all sort
of reasons for updating a kernel, security, sideband
attacks and Android CDD compatibility being the most
obvious ones.
The single firmware file will not be a blocker as the driver
included in updated kernel will support it. All you have to
do is the little effort to re-generate your custom topology
for the new firmware target. The entire operation should not
be a problem as there are dedicated utilities like FDK to do
that.
The issue is the same whether it's a topology file or a
firmware file. The ideal situation is that when the kernel is
updated it handles both in backwards compatible ways.
If to deal with a new firmware file you have to regenerate a
new topology, you are in a different model altogether.
Your statement Pierre suggest that everyone should avoid any
functional changes in kernel that are not critical because
that would be problematic for others who switch from older
kernel version.
All I said was that you cannot assume that people who are
using an old firmware/driver will remain on an old kernel.
Mark made an initial proposal to essentially freeze the
current solution, which would make it possible to update the
kernel but keep the same skylake driver in legacy/maintenance
mode only, and an 'new' option that would rely on an updated
distribution of firmware/driver. I did not get the counter
proposal from Cezary at all.
Ain't my previous message:
-
On the second thought what if instead of duplicating kernel
code, binaries would be duplicated? I.e. rather than targeting
/intel/dsp_fw_cnl.bin, _new_ /skylake would be expecting
/intel/dsp_fw_cnl_release.bin? Same with topology binaries. In
such case, we "only" need to figure out how to propagate new
files to Linux distos so whenever someone updates their kernel,
new binaries are already present in their /lib/firmware.
If such option is valid, we can postpone /skylake upgrade till
5.4 merging window closes and the patches (rough estimation is
150) would descend upon alsa-devel in time between 5.4 and 5.5.
-
a counter proposal?
you didn't explain how the 'duplicated binaries' would be
selected. And 'instead of' means you suggested an alternative to
Mark's proposal.
What I have in mind:
We leave the old stuff as is, e.g:
/lib/firmware/intel/dsp_fw_cnl.bin -> points to _old_ FW binaries
/lib/firmware/<PCI-ID>-INTEL-<oem_data_from_NHLT -> points to old
topology
Existing /skylake i.e. before our initialization refactor would
(kernels <5.5?) would still point to these and since they are not
being removed from linux-firmware, nothing gets broken.
And then we "duplicate" and simply append the new ones:
/lib/firmware/intel/dsp_fw_cnl_release.bin -> points to _new_ FW
/lib/firmware/dfw_cnl_rt274 -> points to _new_ topology
Updated /skylake would simply expect the _new_ files and totally
ignore the old ones i.e.: descriptors would be pointing to
dsp_fw_cnl_release and dfw_cnl_rt274.
What if those new files are not present on the filesystem?
Mark suggested:
"We could have a wrapper which tries to load the newer firmware and uses
the fixed driver code if that's there, otherwise tries the old driver
with the existing firmware paths."
Maybe that's too complicated, I had in mind some sort of opt-in Kconfig
where you only use the new firmware/topology when the user/distro gives
a clear hint than it's fine to use newer stuff.
I also wonder how you are going to deal with all these topology files
with a name derived from the OEM/NHLT. There's just so many of
them...For upstream you probably want to provide ONE per platform
variant, which limits you to the number of machine drivers supported.
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