linux-kernel - RE: [PATCH 2/2] i2c: smbus: Use device_ functions instead of of

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Date:   Fri, 17 Dec 2021 05:31:48 +0000
From:   Akhil R <akhilrajeev@...dia.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Wolfram Sang <wsa@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian Koenig <christian.koenig@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Dmitry Osipenko <digetx@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Krishna Yarlagadda <kyarlagadda@...dia.com>,
        Suresh Mangipudi <smangipudi@...dia.com>
Subject: RE: [PATCH 2/2] i2c: smbus: Use device_ functions instead of of_

> On Thu, Dec 16, 2021 at 6:08 PM Akhil R <akhilrajeev@...dia.com> wrote:
> > > On Thu, Dec 16, 2021 at 3:14 PM Akhil R <akhilrajeev@...dia.com> wrote:
> 
> ...
> 
> > > > -       irq = of_property_match_string(adapter->dev.of_node, "interrupt-
> > > names",
> > > > -                                      "smbus_alert");
> > > > +       irq = device_property_match_string(adapter->dev.parent,
> > > > + "interrupt-
> > > names",
> > > > +                                          "smbus_alert");
> > >
> > > Hmm... Adapter device node is not the same as the node for its parent.
> > > Do you have some code that propagates of_node from parent to child?
> > Adapter device does not have an of_node unless the adapter driver sets
> > it, I guess. I see all the adapter drivers add the of_node and parent
> > for adapter. Also, there are many places in i2c-core-base and
> > i2c-core-acpi where adapter->dev.parent is referred to as the adapter
> > driver device.
> >
> > Basically, adapter->dev.parent and adapter->dev.of_node would
> > ultimately refer to the same device (or the of_node of that device),
> > as far as I understand.
> > >
> > > I.o.w. I would expect to see
> > >
> > >        irq = device_property_match_string(&adapter->dev,
> > > "interrupt-names",
> > >
> > > here.
> > It would then require adding the fw_node as well from the adapter driver.
> > I felt it made more sense to refer adapter->dev.parent here as most of
> > the (or rather all of the) adapter drivers already sets it.
> 
> Is this
> https://elixir.bootlin.com/linux/latest/source/drivers/i2c/i2c-core-base.c#L1047
>
> what you are looking for?
This, I suppose, is for the i2c client driver.
I meant the individual adapter drivers.
https://elixir.bootlin.com/linux/latest/source/drivers/i2c/busses/i2c-tegra.c#L1786
similar is there in all drivers.
If to use adapter->dev for interrupt-names, I assume, it would require to add

	adapter->dev.fwnode = i2c_dev->dev->fwnode;

in all drivers (or at least in the drivers which does not use devicetree).
I thought it would be decent to use adapter->dev.parent as all the drivers already
set it.

> 
> ...
> 
> > > >         if (irq == -EINVAL || irq == -ENODATA)
> > > >                 return 0;
> > > >         else if (irq < 0)
> > >
> > > TBH the entire code smells. "Interesting" way of getting an optional
> > > named interrupt.
> > I felt it useful to have it this way as it would remain agnostic to
> > device tree and the ACPI. We would not have to add redundant codes in
> > adapter drivers that are using ACPI table.
> >
> > Named interrupts for the ACPI as well, I feel would be a useful
> > addition that can prove to be of value more than this change; I believe.
> 
> Me too. My comment was about current state of affairs, and not to your
> change.
Got it :)

Thanks,
Akhil