Message-ID: <8d84916cbebfdbd4db268b501e1c8adc247d1331.camel@redhat.com>
Subject: Re: [PATCH V5 1/6] drivers/mfd: sensehat: Raspberry Pi Sense HAT
 core driver
From:   Nicolas Saenz Julienne <nsaenzju@redhat.com>
To:     Charles Mirabile <cmirabil@redhat.com>,
        linux-kernel@vger.kernel.org
Cc:     Lee Jones <lee.jones@linaro.org>,
        Serge Schneider <serge@raspberrypi.org>,
        Stefan Wahren <stefan.wahren@i2se.com>,
        Mattias Brugger <mbrugger@suse.com>,
        linux-rpi-kernel@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, fedora-rpi@googlegroups.com,
        Mwesigwa Guma <mguma@redhat.com>,
        Joel Savitz <jsavitz@redhat.com>
Date:   Mon, 13 Dec 2021 12:49:48 +0100
In-Reply-To: <20211210221033.912430-2-cmirabil@redhat.com>
References: <20211210221033.912430-1-cmirabil@redhat.com>
         <20211210221033.912430-2-cmirabil@redhat.com>
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Hi Charles,

On Fri, 2021-12-10 at 17:10 -0500, Charles Mirabile wrote:
> This patch adds the core driver file, containing the regmap configuration
> needed to communicate with the board over I2C. We also add the header
> file shared by all three drivers, containing common data and definitions.
> In addition, we add a config option to toggle compilation of the driver.
> 
> Signed-off-by: Charles Mirabile <cmirabil@redhat.com>
> Co-developed-by: Mwesigwa Guma <mguma@redhat.com>
> Signed-off-by: Mwesigwa Guma <mguma@redhat.com>
> Co-developed-by: Joel Savitz <jsavitz@redhat.com>
> Signed-off-by: Joel Savitz <jsavitz@redhat.com>
> ---
>  drivers/mfd/Kconfig          |   8 ++
>  drivers/mfd/Makefile         |   1 +
>  drivers/mfd/sensehat-core.c  | 157 +++++++++++++++++++++++++++++++++++
>  include/linux/mfd/sensehat.h |  51 ++++++++++++
>  4 files changed, 217 insertions(+)
>  create mode 100644 drivers/mfd/sensehat-core.c
>  create mode 100644 include/linux/mfd/sensehat.h
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 3fb480818599..e6de22f98c0e 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -11,6 +11,14 @@ config MFD_CORE
>  	select IRQ_DOMAIN
>  	default n
>  
> +config MFD_SENSEHAT_CORE
> +	tristate "Raspberry Pi Sense HAT core functions"
> +	depends on I2C
> +	select MFD_CORE
> +	help
> +	  This is the core driver for the Raspberry Pi Sense HAT. This provides
> +	  the necessary functions to communicate with the hardware.
> +
>  config MFD_CS5535
>  	tristate "AMD CS5535 and CS5536 southbridge core functions"
>  	select MFD_CORE
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 0b1b629aef3e..2b012e3d497d 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -263,6 +263,7 @@ obj-$(CONFIG_MFD_ROHM_BD718XX)	+= rohm-bd718x7.o
>  obj-$(CONFIG_MFD_ROHM_BD957XMUF)	+= rohm-bd9576.o
>  obj-$(CONFIG_MFD_STMFX) 	+= stmfx.o
>  obj-$(CONFIG_MFD_KHADAS_MCU) 	+= khadas-mcu.o
> +obj-$(CONFIG_MFD_SENSEHAT_CORE) += sensehat-core.o
>  obj-$(CONFIG_MFD_ACER_A500_EC)	+= acer-ec-a500.o
>  obj-$(CONFIG_MFD_QCOM_PM8008)	+= qcom-pm8008.o
>  
> diff --git a/drivers/mfd/sensehat-core.c b/drivers/mfd/sensehat-core.c
> new file mode 100644
> index 000000000000..c5b6f4648d88
> --- /dev/null
> +++ b/drivers/mfd/sensehat-core.c
> @@ -0,0 +1,157 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Raspberry Pi Sense HAT core driver
> + * http://raspberrypi.org
> + *
> + * Copyright (C) 2015 Raspberry Pi
> + * Copyright (C) 2021 Charles Mirabile, Mwesigwa Guma, Joel Savitz
> + *
> + * Original Author: Serge Schneider
> + * Revised for upstream Linux by: Charles Mirabile, Mwesigwa Guma, Joel Savitz
> + *
> + * This driver is based on wm8350 implementation and was refactored to use the
> + * misc device subsystem rather than the deprecated framebuffer subsystem.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/i2c.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/regmap.h>
> +#include <linux/mfd/sensehat.h>
> +
> +#define SENSEHAT_WAI 0xF0
> +#define SENSEHAT_VER 0xF1
> +
> +#define SENSEHAT_ID 's'
> +
> +static struct platform_device *
> +sensehat_client_dev_register(struct sensehat *sensehat, const char *name);
> +
> +static struct regmap_config sensehat_config;
> +
> +static int sensehat_probe(struct i2c_client *i2c,
> +			  const struct i2c_device_id *id)
> +{
> +	int ret;
> +	unsigned int reg;
> +
> +	struct sensehat *sensehat =
> +		devm_kzalloc(&i2c->dev, sizeof(*sensehat), GFP_KERNEL);
> +
> +	if (!sensehat)
> +		return -ENOMEM;
> +
> +	i2c_set_clientdata(i2c, sensehat);
> +	sensehat->dev = &i2c->dev;
> +	sensehat->i2c_client = i2c;
> +
> +	sensehat->regmap =
> +		devm_regmap_init_i2c(sensehat->i2c_client, &sensehat_config);
> +
> +	if (IS_ERR(sensehat->regmap)) {
> +		dev_err(sensehat->dev, "Failed to initialize sensehat regmap");
> +		return PTR_ERR(sensehat->regmap);
> +	}
> +
> +	ret = regmap_read(sensehat->regmap, SENSEHAT_WAI, &reg);
> +	if (ret < 0) {
> +		dev_err(sensehat->dev, "failed to read from device");
> +		return ret;
> +	}
> +
> +	if (reg != SENSEHAT_ID) {
> +		dev_err(sensehat->dev, "expected device ID %i, got %i",
> +			SENSEHAT_ID, ret);
> +		return -EINVAL;
> +	}
> +
> +	ret = regmap_read(sensehat->regmap, SENSEHAT_VER, &reg);
> +	if (ret < 0) {
> +		dev_err(sensehat->dev,
> +			"Unable to get sensehat firmware version");
> +		return ret;
> +	}
> +
> +	dev_info(sensehat->dev, "Raspberry Pi Sense HAT firmware version %i\n",
> +		 reg);

I think both these sections and sensehat_client_dev_register() could be avoided
with a properly configured struct mfd_cell and a call to
devm_mfd_add_devices(). Actually, you're not making use of the mfd subsystem at
all in this driver, which is odd. For an example see 'drivers/mfd/mp2629.c'.

It's easy to get all these device registration operations wrong, so it's always
perfered to use the subsytem facilities when available.

> +
> +#ifdef CONFIG_JOYSTICK_SENSEHAT
> +	sensehat->joystick.pdev =
> +		sensehat_client_dev_register(sensehat, "sensehat-joystick");
> +
> +	if (IS_ERR(sensehat->joystick.pdev)) {
> +		dev_err(sensehat->dev, "failed to register sensehat-joystick");
> +		return PTR_ERR(sensehat->joystick.pdev);
> +	}
> +#endif
> +#ifdef CONFIG_SENSEHAT_DISPLAY
> +
> +	sensehat->display.pdev =
> +		sensehat_client_dev_register(sensehat, "sensehat-display");
> +
> +	if (IS_ERR(sensehat->display.pdev)) {
> +		dev_err(sensehat->dev, "failed to register sensehat-display");
> +		return PTR_ERR(sensehat->display.pdev);
> +	}
> +#endif
> +
> +	return 0;
> +}
> +
> +static struct platform_device *
> +sensehat_client_dev_register(struct sensehat *sensehat, const char *name)
> +{
> +	long ret = -ENOMEM;
> +	struct platform_device *pdev =
> +		platform_device_alloc(name, PLATFORM_DEVID_AUTO);
> +
> +	if (!pdev)
> +		goto alloc_fail;
> +
> +	pdev->dev.parent = sensehat->dev;
> +	platform_set_drvdata(pdev, sensehat);
> +
> +	ret = platform_device_add(pdev);
> +	if (ret)
> +		goto add_fail;
> +
> +	ret = devm_add_action_or_reset(
> +		sensehat->dev, (void *)platform_device_unregister, pdev);
> +	if (ret)
> +		goto alloc_fail;
> +
> +	return pdev;
> +
> +add_fail:
> +	platform_device_put(pdev);
> +alloc_fail:
> +	return ERR_PTR(ret);
> +}
> +
> +static struct regmap_config sensehat_config = {
> +	.name = "sensehat",
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +};
> +
> +static const struct i2c_device_id sensehat_i2c_id[] = {
> +	{ .name = "sensehat" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(i2c, sensehat_i2c_id);
> +
> +static struct i2c_driver sensehat_driver = {
> +	.driver = { .name = "sensehat" },
> +	.probe = sensehat_probe,
> +	.id_table = sensehat_i2c_id,
> +};
> +
> +module_i2c_driver(sensehat_driver);
> +
> +MODULE_DESCRIPTION("Raspberry Pi Sense HAT core driver");
> +MODULE_AUTHOR("Serge Schneider <serge@raspberrypi.org>");
> +MODULE_LICENSE("GPL");

-- 
Nicolás Sáenz