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

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Message-ID: <20241015075121.GA292890@google.com>
Date: Tue, 15 Oct 2024 15:51:21 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
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 Mon, Oct 14, 2024 at 02:25:27PM +0300, Andy Shevchenko wrote:
> On Mon, Oct 14, 2024 at 03:04:44PM +0800, Chen-Yu Tsai wrote:
> > On Thu, Oct 10, 2024 at 11:29 PM Andy Shevchenko
> > <andriy.shevchenko@...ux.intel.com> wrote:
> > > On Tue, Oct 08, 2024 at 03:34:26PM +0800, Chen-Yu Tsai wrote:
> 
> ...
> 
> > > > +static const struct chromeos_i2c_probe_data chromeos_i2c_probe_hana_trackpad = {
> > > > +     .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)
> > >
> > > > +     .opts = &(const struct i2c_of_probe_simple_opts) {
> > >
> > > Perhaps also DEFINE_xxx for this compound literal?
> > 
> > I think it's better to leave this one as is.
> 
> Using a compound literal like this questions the entire approach.

I don't follow. It's a valid use.

> Why you can't you drop it and use the static initializers?

Did you mean split that part out as a separate variable:

	static const struct i2c_of_probe_simple_opts
	chromeos_i2c_probe_voltorb_tch_opts = {
		.res_node_compatible = "elan,ekth6915",
		.supply_name = "vcc33",
		.gpio_name = "reset",
		.post_power_on_delay_ms = 1,
		.post_gpio_config_delay_ms = 300,
		.gpio_assert_to_enable = true,
	};

	static const struct chromeos_i2c_probe_data
	chromeos_i2c_probe_voltorb_touchscreen = {
		.cfg = &chromeos_i2c_probe_simple_touchscreen_cfg,
		.opts = &chromeos_i2c_probe_voltorb_tch_opts,
	};

Instead of the following, which is slightly shorter, and gets rid of one
explicit symbol name:

	static const struct chromeos_i2c_probe_data
	chromeos_i2c_probe_voltorb_touchscreen = {
		.cfg = &chromeos_i2c_probe_simple_touchscreen_cfg,
		.opts = &(const struct i2c_of_probe_simple_opts) {
			.res_node_compatible = "elan,ekth6915",
			.supply_name = "vcc33",
			.gpio_name = "reset",
			.post_power_on_delay_ms = 1,
			.post_gpio_config_delay_ms = 300,
			.gpio_assert_to_enable = true,
		},
	};



ChenYu

> > Not every entry will
> > use the same combination of parameters. And having the entry spelled
> > out like this makes it easier to read which value is for what
> > parameter, instead of having to go up to the macro definition.
> > 
> > For comparison, this entry uses just two of the parameters, while for
> > another platform I'm working on the full set of parameters is needed.
> > 
> > > > +             .res_node_compatible = "elan,ekth3000",
> > > > +             .supply_name = "vcc",
> > > > +             /*
> > > > +              * ELAN trackpad needs 2 ms for H/W init and 100 ms for F/W init.
> > > > +              * Synaptics trackpad needs 100 ms.
> > > > +              * However, the regulator is set to "always-on", presumably to
> > > > +              * avoid this delay. The ELAN driver is also missing delays.
> > > > +              */
> > > > +             .post_power_on_delay_ms = 0,
> > > > +     }
> > > > +};
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
>