linux-kernel - Re: [PATCH v2] driver core: Remove device link creation limitation

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Message-ID: <CAGETcx9oqAJ-VoJnD0Y8k+W8cCGPDz--=amktSgW_sB4MEngDA@mail.gmail.com>
Date:   Mon, 29 Jul 2019 14:43:01 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Dmitry Osipenko <digetx@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Lukas Wunner <lukas@...ner.de>,
        Jon Hunter <jonathanh@...dia.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Thierry Reding <thierry.reding@...il.com>
Subject: Re: [PATCH v2] driver core: Remove device link creation limitation

On Mon, Jul 29, 2019 at 2:25 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Mon, Jul 29, 2019 at 10:47 PM Saravana Kannan <saravanak@...gle.com> wrote:
> >
> > Rafael,
> >
> > This is the fix you need. Or something link this.
> >
> > I had asked you to reject DL_FLAG_MANAGED as an input flag if you are
> > marking it as internal (in the comments). But looks like you were also
> > trying to check for "undefined" bit positions. However, the check
> > isn't correct because DL_MANAGED_FLAGS doesn't include (rightfully so)
> > DL_FLAG_PM_RUNTIME and DL_FLAG_RPM_ACTIVE .
> >
> > I tried to write a DL_FLAG_EXTERNAL to include all the external flags,
> > but that felt like a maintenance headache that's not worth carrying. I
> > think it's simpler to just error out when internal flags being passed
> > in and ignore any undefined bit positions.
>
> Well, IMO it is better to prevent people from passing unrecognized
> flags to device_link_add() at all, even if that means some extra
> effort when adding new flags.

It isn't so much the extra effort that's a concern, but people might
miss updating whatever grouping macro we use.

>
> I'll post an alternative fix shortly.

You might want to move the MANAGED_FLAGs and other grouping macros
into the header file then? So that if someone is adding new flags,
it'll be less likely they'll forget to update the grouping macro?

-Saravana