linux-kernel - Re: [PATCH v5 3/5] mfd: p3h2x4x: Add driver for NXP P3H2x4x i3c hub and on-die regulator

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Message-ID: <ffb00660-9fb4-4c89-9032-f003d002e989@kernel.org>
Date: Fri, 6 Feb 2026 13:52:03 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Aman Kumar Pandey <aman.kumarpandey@....com>,
 linux-kernel@...r.kernel.org, linux-i3c@...ts.infradead.org,
 alexandre.belloni@...tlin.com, krzk+dt@...nel.org, robh@...nel.org,
 conor+dt@...nel.org, devicetree@...r.kernel.org, broonie@...nel.org,
 lee@...nel.org, Frank.Li@....com, lgirdwood@...il.com
Cc: vikash.bansal@....com, priyanka.jain@....com,
 shashank.rebbapragada@....com
Subject: Re: [PATCH v5 3/5] mfd: p3h2x4x: Add driver for NXP P3H2x4x i3c hub
 and on-die regulator

On 06/02/2026 13:01, Aman Kumar Pandey wrote:
> Add core MFD support for the NXP P3H2x4x (P3H2440/P3H2441/P3H2840/P3H2841)
> family of multiport I3C hub devices. These devices connect to a host via
> I3C/I2C/SMBus and expose multiple downstream target ports.
> 
> This patch introduces the MFD driver that registers sub-devices for the
> I3C hub and on-die regulators.

Drop sentence. You already said it in the first place, didn't you?

Please do not use "This commit/patch/change", but imperative mood. See
longer explanation here:
https://elixir.bootlin.com/linux/v6.16/source/Documentation/process/submitting-patches.rst#L94

...


> +
> +	i2c_set_clientdata(client, p3h2x4x);
> +
> +	p3h2x4x->regmap = devm_regmap_init_i2c(client, &p3h2x4x_regmap_config);
> +	if (IS_ERR(p3h2x4x->regmap)) {

Drop {} now. When you change piece of the code, fix rest as well.

See Linux coding style.

> +		return dev_err_probe(&client->dev, PTR_ERR(p3h2x4x->regmap),
> +				     "Failed to register I3C HUB regmap\n");
> +	}
> +
> +	p3h2x4x->is_p3h2x4x_in_i3c = false;
> +	p3h2x4x->i2c_client = client;
> +
> +	ret = devm_mfd_add_devices(&client->dev, PLATFORM_DEVID_NONE,
> +				   p3h2x4x_devs, ARRAY_SIZE(p3h2x4x_devs),
> +				   NULL, 0, NULL);
> +	if (ret)
> +		return dev_err_probe(&client->dev, ret, "Failed to add sub devices\n");
> +
> +	return 0;
> +}
> +
> +/* p3h2x4x ids (i3c) */
> +static const struct i3c_device_id p3h2x4x_i3c_ids[] = {
> +	I3C_CLASS(I3C_DCR_HUB, NULL),
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(i3c, p3h2x4x_i3c_ids);
> +
> +/* p3h2x4x ids (i2c) */
> +static const struct i2c_device_id p3h2x4x_i2c_id_table[] = {
> +	{ "nxp-i3c-hub" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(i2c, p3h2x4x_i2c_id_table);
> +
> +static const struct of_device_id  p3h2x4x_i2c_of_match[] = {
> +	{ .compatible = "nxp,p3h2840", },
> +	{ /* sentinel */ }
> +};
> +
> +MODULE_DEVICE_TABLE(of, p3h2x4x_i2c_of_match);
> +static struct i3c_driver p3h2x4x_i3c = {
> +	.driver = {
> +		.name = "p3h2x4x_i3c_drv",
> +	},
> +	.probe = p3h2x4x_device_probe_i3c,
> +	.id_table = p3h2x4x_i3c_ids,
> +};
> +
> +static struct i2c_driver p3h2x4x_i2c = {
> +	.driver = {
> +		.name = "p3h2x4x_i2c_drv",
> +		.of_match_table = p3h2x4x_i2c_of_match,
> +	},
> +	.probe =  p3h2x4x_device_probe_i2c,
> +	.id_table = p3h2x4x_i2c_id_table,
> +};
> +
> +module_i3c_i2c_driver(p3h2x4x_i3c, &p3h2x4x_i2c);
> +
> +MODULE_AUTHOR("Aman Kumar Pandey <aman.kumarpandey@....com>");
> +MODULE_AUTHOR("vikash Bansal <vikash.bansal@....com>");
> +MODULE_DESCRIPTION("P3H2x4x I3C HUB multi function driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/mfd/p3h2840.h b/include/linux/mfd/p3h2840.h
> new file mode 100644
> index 000000000000..b7a9c7f3aa4d
> --- /dev/null
> +++ b/include/linux/mfd/p3h2840.h
> @@ -0,0 +1,28 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright 2025 NXP
> + * This header file contain private Reg address and its bit mapping etc.
> + */
> +
> +#ifndef P3H2840_H
> +#define P3H2840_H

That's pretty poor (too simple) guard for a global header.

> +
> +#include <linux/types.h>
> +
> +/* Device Configuration Registers */
> +#define P3H2x4x_DEV_REG_PROTECTION_CODE				0x10
> +#define P3H2x4x_REGISTERS_LOCK_CODE				0x00
> +#define P3H2x4x_REGISTERS_UNLOCK_CODE				0x69
> +#define P3H2x4x_CP1_REGISTERS_UNLOCK_CODE			0x6a
> +


Best regards,
Krzysztof