linux-kernel - Re: [PATCH v8 7/8] platform/chrome: Introduce device tree hardware prober

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Message-ID: <Zw5mEv_cnZzPUqII@smile.fi.intel.com>
Date: Tue, 15 Oct 2024 15:54:42 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Chen-Yu Tsai <wenst@...omium.org>
Cc: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Wolfram Sang <wsa@...nel.org>, Benson Leung <bleung@...omium.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>, chrome-platform@...ts.linux.dev,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Douglas Anderson <dianders@...omium.org>,
	Johan Hovold <johan@...nel.org>, Jiri Kosina <jikos@...nel.org>,
	linux-i2c@...r.kernel.org
Subject: Re: [PATCH v8 7/8] platform/chrome: Introduce device tree hardware
 prober

On Tue, Oct 15, 2024 at 08:18:50PM +0800, Chen-Yu Tsai wrote:
> On Tue, Oct 15, 2024 at 7:24 PM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> > On Tue, Oct 15, 2024 at 02:32:54PM +0800, Chen-Yu Tsai wrote:
> > > On Mon, Oct 14, 2024 at 7:23 PM Andy Shevchenko
> > > <andriy.shevchenko@...ux.intel.com> wrote:
> > > > On Mon, Oct 14, 2024 at 12:56:20PM +0800, Chen-Yu Tsai wrote:
> > > > > On Thu, Oct 10, 2024 at 11:32 PM Andy Shevchenko
> > > > > <andriy.shevchenko@...ux.intel.com> wrote:
> > > > > > On Thu, Oct 10, 2024 at 06:29:44PM +0300, Andy Shevchenko wrote:
> > > > > > > On Tue, Oct 08, 2024 at 03:34:26PM +0800, Chen-Yu Tsai wrote:

...

> > > > > > > > +   .cfg = &chromeos_i2c_probe_simple_trackpad_cfg,
> > > > > > >
> > > > > > >       .cfg = DEFINE_I2C_OF_PROBE_CFG(trackpad, i2c_of_probe_simple_ops),
> > > > > > >
> > > > > > > Or even
> > > > > > >
> > > > > > > #define DEFINE_I2C_OF_PROBE_CFG_SIMPLE(_type_)                        \
> > > > > > >       DEFINE_I2C_OF_PROBE_CFG(type, &i2c_of_probe_simple_ops)
> > > > >
> > > > > I'm not inclined on using compound literals here. "simple X cfg" will
> > > > > likely get shared between multiple |chromeos_i2c_probe_data| entries,
> > > > > and AFAIK the toolchain can't merge them. So we would end up with one
> > > > > compound literal per entry, even if their contents are the same.
> > > >
> > > > I'm not sure I follow, you are using compound literal _already_.
> > > > How does my proposal change that?
> > >
> > > I'm using it where it makes sense, i.e. where the embedded variable
> > > is not going to be shared with other instances.
> > >
> > > For the dumb probers, there's only going to be one instance per "type".
> > >
> > > For the simple probers, the config part is still one instance per "type",
> > > but the parameters are board and component specific. There will be
> > > multiple instances. Hence the config part can be shared, while the
> > > parameters likely won't be.
> > >
> > > > > > With that also looking at the above
> > > > > >
> > > > > > #define DEFINE_I2C_OF_PROBE_CFG_NONE(_type_)                            \
> > > > > >         DEFINE_I2C_OF_PROBE_CFG(type, NULL)
> > > > >
> > > > > For the "dumb" case it makes sense though, since it would be one instance
> > > > > per type. But we could go further and just wrap the whole
> > > > > |chromeos_i2c_probe_data| declaration.
> > > >
> > > > Maybe it's too far from now...
> > >
> > > This is what I have:
> > >
> > > #define DEFINE_CHROMEOS_I2C_PROBE_DATA_DUMB(_type)
> > >                         \
> > >        static const struct chromeos_i2c_probe_data
> > > chromeos_i2c_probe_dumb_ ## _type = {       \
> >
> > >                .cfg = &(const struct i2c_of_probe_cfg) {
> >
> > But the below is static initializer, why do you need a compound literal here?
> 
> Because .cfg takes a pointer to a struct. It's not an embedded struct.
> The compound literal creates the internal struct, and then its address
> is taken and assigned to the .cfg field.
> 
> Does that make sense?

Okay, I see now. Yeah, I have no preferences here, I saw the code like in split
version or like in yours. I _slightly_ bend to non-compound literal variant,
but again here it might be not worth doing a such.

> > >                         \
> > >                        .type = #_type,
> > >                         \
> > >                },
> > >                         \
> > > };
> > >
> > > DEFINE_CHROMEOS_I2C_PROBE_DATA_DUMB(touchscreen);
> >
> > s/dumb/simple/g
> 
> "simple" is taken. This is "dumb" as in it does not need any helpers.
> Maybe "no-op" if you don't like the negative connotation?

_BY_TYPE ?

-- 
With Best Regards,
Andy Shevchenko