linux-kernel - Re: [PATCH RESEND v2] interconnect: drop unused icc

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Date:   Wed, 21 Jun 2023 07:10:07 -0700
From:   Mike Tipton <quic_mdtipton@...cinc.com>
To:     Johan Hovold <johan@...nel.org>
CC:     Johan Hovold <johan+linaro@...nel.org>,
        Georgi Djakov <djakov@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Odelu Kukatla <quic_okukatla@...cinc.com>
Subject: Re: [PATCH RESEND v2] interconnect: drop unused icc_get() interface

On 6/21/2023 1:34 AM, Johan Hovold wrote:
> On Tue, Jun 20, 2023 at 02:57:17PM -0700, Mike Tipton wrote:
>> On 5/23/2023 2:52 AM, Johan Hovold wrote:
>>> The icc_get() interface can be used to lookup an interconnect path based
>>> on global node ids. There has never been any users of this interface and
>>> all lookups are currently done from the devicetree.
>>>
>>> Remove the unused icc_get() interface.
>>>
>>> Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> 
>> We have downstream debug/test modules that removing icc_get() will
>> break. I'd like to get equivalent debug support in mainline, but until
>> then I'd prefer we not remove this.
> 
> I'm sure you've heard this before, but if it's not in mainline it does
> not count. We don't carry code upstream for the sole benefit of
> out-of-tree users.

Yeah, I understand that in general.

> 
>> I suspect having a mainline approach for voting paths from debugfs would
>> be useful to others as well. There are similar debugfs control
>> mechanisms in other frameworks already, e.g. clock.
>>
>> Instead of removing icc_get() immediately, can we wait for a future
>> patch series that adds debugfs as a consumer?
> 
> This function was merged over four years ago and has never been used in
> mainline and I doubt a user will suddenly show up in the near future if
> we were to keep it.

I guess I'm hoping if it's already been unused in mainline for four 
years, that we can keep it a little longer until the mainline debugfs 
user can be added.

We can prepare that series. Not entirely sure when it'll be ready, but 
can try to prioritize it.

> 
> I guess you can just carry one more patch out-of-tree until you can
> mainline a proper debugfs interface (which should probably not even use
> this function, as you mentioned yourself).
That's not really possible in this case. We're limited to our DLKMs 
running on top of the Android kernel. We can't modify the interconnect 
framework itself.

> 
> Johan