linux-kernel - Re: [PATCH] PM: opp: Fix NULL pointer exception on a v2 table combined with v1 opps

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Date:   Mon, 4 Apr 2022 08:28:54 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        Dmitry Osipenko <digetx@...il.com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM: opp: Fix NULL pointer exception on a v2 table
 combined with v1 opps

On 04/04/2022 08:26, Viresh Kumar wrote:
> On 01-04-22, 14:03, Krzysztof Kozlowski wrote:
>> dev_pm_opp_add() adds a v1 OPP.  If the Devicetree contains an OPP v2
>> table with required-opps, but the driver uses dev_pm_opp_add(), the
>> table might have required_opp_count!=0 but the opp->required_opps will
>> be NULL.
> 
> This use-case isn't supported currently, as either all OPPs should
> have required-opp or none. This kind of scenario may end up breaking
> at other places later on, as I have designed this stuff with the
> above assumption.

I understand this is not a proper use case, but it is easy to trigger
(UFS driver adds opps manually, DTS also adds one). Maybe you prefer to
handle it differently - exit with ERRNO? Because NULL pointer exception
in case of proper, but unexpected DTB is not a good way to handle it.

Best regards,
Krzysztof