linux-kernel - Re: Firmware versioning best practices II

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Date:	Mon, 22 Feb 2010 11:14:15 -0800
From:	"Luis R. Rodriguez" <mcgrof@...il.com>
To:	Marcel Holtmann <marcel@...tmann.org>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Johannes Berg <johannes@...solutions.net>,
	linux-kernel@...r.kernel.org,
	linux-wireless <linux-wireless@...r.kernel.org>,
	Vipin Mehta <Vipin.Mehta@...eros.com>
Subject: Re: Firmware versioning best practices II

On Sun, Feb 21, 2010 at 2:13 AM, Marcel Holtmann <marcel@...tmann.org> wrote:
> Hi David,
>
>> > > > That doesn't make much sense anyway. If the firmware filename is
>> > > > foo-$APIVER-$CODEVER every code change would need a corresponding
>> > > driver
>> > > > change. If it is just foo-$APIVER then the $CODEVER can be embedded
>> > > in
>> > > > the firmware file and printed so you know which code you're using,
>> > > but
>> > > > if it doesn't influence the API I don't see why it should be part of
>> > > the
>> > > > filename?
>> > >
>> > > The idea is that just like with shared libraries, you have a symlink
>> > > from the 'soname' foo-3.fw to the actual file foo-3-1.4.1.fw.
>> >
>> > Ah ok. I indeed do that manually with iwlwifi firmware :)
>> >
>> > > For shared libraries, it's easy to create those symlinks automatically
>> > > using ldconfig. For firmware that doesn't really work though -- since
>> > > the soname isn't encoded in the file like it is in ELF libraries.
>> >
>> > Right. Though I guess we could come up with a unified firmware wrapper
>> > format that the firmware loader can unwrap.
>>
>> I suppose we could, but this seems like overkill to me.
>
> I have to agree. This looks like total overkill to me.
>
> Just use the $APIVER in the firmware filename.

OK -- so what goes into linux-firmware is just the latest

foo-$(API)

> And if someone wants to
> keep track of more details then they can manually symlink them.

Well do we want the older foo-$(API)-$(VAR) files in linux-firmware
too for those companies/developers wishing to do this?

What about deprecating APIs of the firmware based on kernel releases.
I see it reasonable to deprecate a firmware API completely for a
future kernel release provided you maintain all features and
functionality in par. Does that sound reasonable?

> Unless we have full control over the source code of every firmware used
> in the kernel, why bother. It is up to the companies providing them
> anyway to make sure everything works as expected and the community can't
> fix it.

Well that's exactly it -- we do have access to the code for ar9170 for
example, so these details will become more relevant in the future.

 Luis
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