Subject: Re: [PATCH V5 1/6] drivers/mfd: sensehat: Raspberry Pi Sense HAT core
 driver
To:     Charles Mirabile <cmirabil@redhat.com>,
        linux-kernel@vger.kernel.org
Cc:     Lee Jones <lee.jones@linaro.org>,
        Serge Schneider <serge@raspberrypi.org>,
        Nicolas Saenz Julienne <nsaenzju@redhat.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>
References: <20211210221033.912430-1-cmirabil@redhat.com>
 <20211210221033.912430-2-cmirabil@redhat.com>
From:   Stefan Wahren <stefan.wahren@i2se.com>
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Message-ID: <50355fae-0745-c8a9-87f9-2a7491cd2c17@i2se.com>
Date:   Sun, 12 Dec 2021 12:43:30 +0100
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Am 10.12.21 um 23:10 schrieb Charles Mirabile:
> 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/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>
Is this header really necessary?
> +#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);
Please avoid this forward declaration
> +
> +static struct regmap_config sensehat_config;
Is there a specific reason, why the driver only supports one sense hat?
> +
> +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");
I think the return code of regmap_read could be helpful in the log entry.
> +		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);
> +
> +#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
Please replace the #ifdev blocks with IS_ENABLED() to increase compile
coverage