Hi again,
On Thu, Jan 03, 2019 at 04:11:58PM -0800, Brian Norris wrote:
> On Thu, Jan 03, 2019 at 04:01:45PM -0800, Bjorn Andersson wrote:
> > I share your concern about this, but I came to suggest this as the
> > driver cares about platforms but the firmware is (often?)
> > device/product-specific.
> >
> > E.g. we will serve the MTP and Pixel 3 with the qcom,sdm845-adsp-pas
> > compatible, but they are unlikely to run the same adsp firmware. This
> > allows the individual dtb to specify which firmware the driver should
> > use.
>
> I understand this, but that still doesn't mean we should be suggesting
> each DTB to clutter the top-level firmware search path, especially since
> lazy people will probably just use "modem.mdt" and similar. That means
> you no longer can ship the same rootfs that supports both QCOM and
> <other> modems, if <other> modem also uses the same lazy format.
>
> It seems like a much better practice to at least enforce a particular
> prefix to things. e.g., the driver could assume:
>
> qcom/sdm845-adsp-pas/ (or if you must, just qcom/)
>
> and your DTB only gets to add .../<your-string-here> to that path.
>
> In case it isn't clear: I think it's also severely misguided that the
> existing driver gets away with lines like
>
> request_firmware(&fw, "modem.mdt", ...);
>
> today ;)
To add to my thoughts, since I think maybe Sibi was a little unclear of
my thoughts:
One of my primary concerns with the existing approach is that it's
basically a complete free-for-all. We should have some minimal standards
(enforced in code) such that our DTB can never point us at something
like /lib/firmware/<other-vendor>/foo.bin (or /lib/firmware/modem.mdt;
or lots of other bad examples). This could probably be done simply by
always prefixing 'qcom/' (I don't remember -- does request_firmware()
follow '..'? e.g., 'firmware-name = "../bar/foo.bin"'.)
As a bonus: it would be very nice if we can provide a little more
structure by default, and avoid arbitrary hierarchy in the DTS. That's
where I brought up ath10k's "variant" as an example; if we can use
'compatible' to capture most of this particular Hexagon core's
properties, then we only leave a single level of variability to the DTS.
But I might be off-base with the "bonus" paragraph. So I'd also be
somewhat happy with something much less ambitious, like just a built-in
prefix ('qcom/').
And you can also just ignore my thoughts entirely (and I'll be even less
happy), since Rob did already provide his Reviewed-by ;) I mostly wanted
to give food for thought, in the hopes that something in here would help
improve this a bit.
Regards,
Brian
