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Subject: Re: [RFC PATCH 1/3] drivers/mfd: rpisense: Raspberry Pi senseHAT core
 driver
To:     Joel Savitz <jsavitz@redhat.com>, linux-kernel@vger.kernel.org
Cc:     Lee Jones <lee.jones@linaro.org>,
        Nicolas Saenz Julienne <nsaenzju@redhat.com>,
        linux-rpi-kernel@lists.infradead.org, fedora-rpi@googlegroups.com,
        Charles Mirabile <cmirabil@redhat.com>,
        Mwesigwa Guma <mguma@redhat.com>
References: <20210807002722.2634585-1-jsavitz@redhat.com>
 <20210807002722.2634585-2-jsavitz@redhat.com>
From:   Stefan Wahren <stefan.wahren@i2se.com>
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Message-ID: <e22d5757-92fa-1371-44cc-fa2cf172ec70@i2se.com>
Date:   Sat, 7 Aug 2021 11:53:22 +0200
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In-Reply-To: <20210807002722.2634585-2-jsavitz@redhat.com>
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Am 07.08.21 um 02:27 schrieb Joel Savitz:
> This patch adds the core driver file, containing methods 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>
> Signed-off-by: Mwesigwa Guma <mguma@redhat.com>
> Signed-off-by: Joel Savitz <jsavitz@redhat.com>
> ---
>  drivers/mfd/Kconfig          |  10 +++
>  drivers/mfd/Makefile         |   1 +
>  drivers/mfd/rpisense-core.c  | 170 +++++++++++++++++++++++++++++++++++
>  include/linux/mfd/rpisense.h |  55 ++++++++++++
>  4 files changed, 236 insertions(+)
>  create mode 100644 drivers/mfd/rpisense-core.c
>  create mode 100644 include/linux/mfd/rpisense.h
>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 6a3fd2d75f96..614de080dee6 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -11,6 +11,16 @@ config MFD_CORE
>  	select IRQ_DOMAIN
>  	default n
>  
> +config MFD_RPISENSE
RPI is not used before in config options. I suggest MFG_RASPBERRYPI_SENSE
> +	tristate "Raspberry Pi Sense HAT driver"
> +	depends on I2C && GPIOLIB
> +	select MFD_CORE
> +	help
> +	  This is the driver for the Raspberry Pi Sense HAT. This provides
> +	  the necessary functions to communicate with the hardware as well
> +	  as a joystick and display interface. Linux communicates with the
> +	  hardwire using the GPIO pins via the I2C protocol.
> +
>  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 8116c19d5fd4..76f9a9221241 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-$(CONFIG_MFD_RPISENSE) 	+= rpisense-core.o
>  obj-$(CONFIG_MFD_ACER_A500_EC)	+= acer-ec-a500.o
>  obj-$(CONFIG_MFD_QCOM_PM8008)	+= qcom-pm8008.o
>  
> diff --git a/drivers/mfd/rpisense-core.c b/drivers/mfd/rpisense-core.c
> new file mode 100644
> index 000000000000..69e3051a4be0
> --- /dev/null
> +++ b/drivers/mfd/rpisense-core.c
> @@ -0,0 +1,170 @@
> +// 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/mfd/rpisense.h>
> +
> +#define RPISENSE_DISPLAY		0x00
> +#define RPISENSE_WAI			0xF0
> +#define RPISENSE_VER			0xF1
> +#define RPISENSE_KEYS			0xF2
> +#define RPISENSE_EE_WP			0xF3
> +
> +#define RPISENSE_ID			's'
> +
> +static struct platform_device *
> +rpisense_client_dev_register(struct rpisense *rpisense, const char *name);
> +
> +static int rpisense_probe(struct i2c_client *i2c,
> +			       const struct i2c_device_id *id)
> +{
> +	int ret;
> +
> +	struct rpisense *rpisense = devm_kzalloc(&i2c->dev, sizeof(*rpisense), GFP_KERNEL);
> +
> +	if (rpisense == NULL)
> +		return -ENOMEM;
The more common style is: if (!rpisense)
> +
> +	i2c_set_clientdata(i2c, rpisense);
> +	rpisense->dev = &i2c->dev;
> +	rpisense->i2c_client = i2c;
> +
> +
> +	ret = i2c_smbus_read_byte_data(rpisense->i2c_client, RPISENSE_WAI);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (ret != RPISENSE_ID)
> +		return -EINVAL;
> +
> +	ret = i2c_smbus_read_byte_data(rpisense->i2c_client, RPISENSE_VER);
> +	if (ret < 0)
> +		return ret;
Not sure about all the error cases, but i think the last two deserve a
log entry.
> +
> +	dev_info(rpisense->dev,
> +		 "Raspberry Pi Sense HAT firmware version %i\n", ret);
> +
> +	rpisense->joystick.pdev = rpisense_client_dev_register(rpisense,
> +							       "rpi-sense-js");
> +
> +	if (IS_ERR(rpisense->joystick.pdev)) {
> +		dev_err(rpisense->dev, "failed to register rpisense-js");
> +		return PTR_ERR(rpisense->joystick.pdev);
> +	}
> +
> +	rpisense->display.pdev = rpisense_client_dev_register(rpisense,
> +								  "rpi-sense-fb");
> +
> +	if (IS_ERR(rpisense->display.pdev)) {
> +		dev_err(rpisense->dev, "failed to register rpisense-fb");
> +		return PTR_ERR(rpisense->display.pdev);
> +	}
> +
> +	return 0;
> +}
> +
> +static struct platform_device *
> +rpisense_client_dev_register(struct rpisense *rpisense, const char *name)
> +{
> +	long ret = -ENOMEM;
> +	struct platform_device *pdev = platform_device_alloc(name, -1);
> +
> +	if (pdev == NULL)
> +		goto alloc_fail;
> +
> +	pdev->dev.parent = rpisense->dev;
> +	platform_set_drvdata(pdev, rpisense);
> +
> +	ret = platform_device_add(pdev);
> +	if (ret != 0)
Similiar as above: if (ret)
> +		goto add_fail;
> +
> +	ret = devm_add_action_or_reset(rpisense->dev,
> +		(void *)platform_device_unregister, pdev);
> +	if (ret != 0)
> +		goto alloc_fail;
> +
> +	return pdev;
> +
> +add_fail:
> +	platform_device_put(pdev);
> +alloc_fail:
> +	return ERR_PTR(ret);
> +}
> +
> +int rpisense_get_joystick_state(struct rpisense *rpisense)
> +{
> +	int ret = i2c_smbus_read_byte_data(rpisense->i2c_client, RPISENSE_KEYS);
> +
> +	return ret < 0 ? ret : ret & 0x1f;
> +}
> +EXPORT_SYMBOL_GPL(rpisense_get_joystick_state);
> +
> +int rpisense_update_display(struct rpisense *rpisense)
> +{
> +	int i, j, ret;
> +	struct rpisense_display *display = &rpisense->display;
> +	struct {u8 reg, pixel_data[8][3][8]; } msg;
> +
> +	msg.reg = RPISENSE_DISPLAY;
> +	for (i = 0; i < 8; ++i) {
> +		for (j = 0; j < 8; ++j) {
> +			msg.pixel_data[i][0][j] = display->gamma[display->vmem[i][j].r];
> +			msg.pixel_data[i][1][j] = display->gamma[display->vmem[i][j].g];
> +			msg.pixel_data[i][2][j] = display->gamma[display->vmem[i][j].b];
> +		}
> +	}
> +
> +	ret = i2c_master_send(rpisense->i2c_client, (u8 *)&msg, sizeof(msg));
> +	if (ret < 0)
> +		dev_err(rpisense->dev, "Update to 8x8 LED matrix display failed");
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(rpisense_update_display);
> +
> +static const struct i2c_device_id rpisense_i2c_id[] = {
> +	{ "rpi-sense", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, rpisense_i2c_id);
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id rpisense_core_id[] = {
> +	{ .compatible = "rpi,rpi-sense" },

The vendor is raspberrypi, which is already listed in Documentation
<https://elixir.bootlin.com/linux/latest/source/Documentation>/devicetree
<https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree>/bindings
<https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings>/vendor-prefixes.yaml
<https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/vendor-prefixes.yaml>

Not sure about the compatible. It must be added to the bindings, but
unsure this should go to Documentation
<https://elixir.bootlin.com/linux/latest/source/Documentation>/devicetree
<https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree>/bindings
<https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings>/trivial-devices.yaml
<https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/trivial-devices.yaml>
or a separate YAML file.

Best regards