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From: Rob Herring <email@example.com>
To: Saravana Kannan <firstname.lastname@example.org>
Cc: Greg Kroah-Hartman <email@example.com>,
"Rafael J. Wysocki" <firstname.lastname@example.org>,
Frank Rowand <email@example.com>,
Len Brown <firstname.lastname@example.org>, Ulf Hansson <email@example.com>,
Android Kernel Team <firstname.lastname@example.org>,
"open list:ACPI FOR ARM64 (ACPI/arm64)"
Subject: Re: [PATCH v1 2/2] of: platform: Mark bus devices nodes with FWNODE_FLAG_NEVER_PROBES
Date: Thu, 2 Sep 2021 14:02:58 -0500 [thread overview]
Message-ID: <CAL_Jsq+A1T5+KK5xsVVtrMVeuMre3B6sAAroX+a3gQy6wY+r8A@mail.gmail.com> (raw)
On Thu, Sep 2, 2021 at 11:57 AM Saravana Kannan <email@example.com> wrote:
> On Thu, Sep 2, 2021 at 7:24 AM Rob Herring <firstname.lastname@example.org> wrote:
> > On Wed, Sep 1, 2021 at 9:55 PM Saravana Kannan <email@example.com> wrote:
> > >
> > > We don't want fw_devlink creating device links for bus devices as
> > > they'll never probe. So mark those device node with this flag.
> > >
> > > Signed-off-by: Saravana Kannan <firstname.lastname@example.org>
> > > ---
> > > drivers/of/platform.c | 16 ++++++++++++++++
> > > 1 file changed, 16 insertions(+)
> > >
> > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > > index 74afbb7a4f5e..42b3936d204a 100644
> > > --- a/drivers/of/platform.c
> > > +++ b/drivers/of/platform.c
> > > @@ -392,6 +392,22 @@ static int of_platform_bus_create(struct device_node *bus,
> > > if (!dev || !of_match_node(matches, bus))
> > > return 0;
> > >
> > > + /*
> > > + * If the bus node has only one compatible string value and it has
> > > + * matched as a bus node, it's never going to get probed by a device
> > > + * driver. So flag it as such so that fw_devlink knows not to create
> > > + * device links with this device.
> > > + *
> > > + * This doesn't catch all devices that'll never probe, but this is good
> > > + * enough for now.
> > > + *
> > > + * This doesn't really work for PPC because of how it uses
> > > + * of_platform_bus_probe() to add normal devices. So ignore PPC cases.
> > > + */
> > > + if (!IS_ENABLED(CONFIG_PPC) &&
> > > + of_property_count_strings(bus, "compatible") == 1)
> > > + bus->fwnode.flags |= FWNODE_FLAG_NOT_DEVICE;
> > This looks fragile relying on 1 compatible string, and the DT flags in
> > this code have been fragile too. I'm pretty sure we have cases of
> > simple-bus or simple-mfd that also have another compatible.
> > Couldn't we solve this with a simple driver?
> Oh, I didn't think you'd like that. I'd lean towards that option too
> if we can address some of the other concerns below.
> > Make 'simple-pm-bus'
> > driver work for other cases?
> > BTW, this patch doesn't even work for
> > simple-pm-bus.
> How do you mean? Because simple-pm-bus already has a driver and
> doesn't set "matches" param when it calls of_platform_populate() and
> this flag won't be set. So at least for simple-pm-bus I don't see any
> I was trying to reuse of_default_bus_match_table without explicitly
> referring to it, but if it's confusing I can add a separate list of
> compatible strings and use those here instead of using "matches".
What happens with a non-default table? I'm not sure we can assume the
> > A driver for simple-bus may cause issues if there's a
> > more specific driver to bind to as we don't handle that. It's simply
> > whichever matches first.
> Right, this is my worry. Especially for devices like this (there are
> plenty of cases like this) which have a driver that probes them but
> also lists simple-bus
Uhh, that one is certainly a leakage of wanting an soc_device in the
hierarchy, not any real bus structure reflecting the h/w. I'm not a
fan of the soc_device stuff and its optional nature. Everything is an
SoC, so it should always be there? Or your device hierarchy should
change when you decide to add a soc_device?
> So as long as there's a compatible string that's not one of the
> "transparent" busses, this driver shouldn't match. So, I don't think I
> can get away from checking the compatible strings.
> How about I check here to make sure all the "compatible" strings are
> from an approved transparent bus list, and if it's true, I use
> driver_override to force match it to a transparent bus driver? Would
> you be okay with that?
Can't we do that within a driver? We check this and fail probe if
there's a more specific compatible. Then another driver can match and
next prev parent reply other threads:[~2021-09-02 19:03 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-02 2:55 [PATCH v1 0/2] Ulf reported an issue with fw_devlink. This series tries to fix that issue Saravana Kannan
2021-09-02 2:55 ` [PATCH v1 1/2] driver core: Add support for FWNODE_FLAG_NEVER_PROBES Saravana Kannan
2021-09-02 2:55 ` [PATCH v1 2/2] of: platform: Mark bus devices nodes with FWNODE_FLAG_NEVER_PROBES Saravana Kannan
2021-09-02 14:24 ` Rob Herring
2021-09-02 16:57 ` Saravana Kannan
2021-09-02 19:02 ` Rob Herring [this message]
2021-09-02 19:28 ` Saravana Kannan
2021-09-03 0:53 ` Rob Herring
2021-09-03 1:15 ` Saravana Kannan
2021-09-03 14:58 ` Rob Herring
2021-09-03 17:06 ` Saravana Kannan
2021-09-03 17:37 ` Rafael J. Wysocki
2021-09-02 17:20 ` Saravana Kannan
2021-09-02 2:56 ` [PATCH v1 0/2] Ulf reported an issue with fw_devlink. This series tries to fix that issue Saravana Kannan
2021-09-02 15:56 ` Rafael J. Wysocki
2021-09-02 16:27 ` Saravana Kannan
2021-09-02 16:31 ` Rafael J. Wysocki
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