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Date: Thu, 8 Sep 2022 12:26:37 -0300
From: Wander Lairson Costa <wander@...hat.com>
To: Charles Mirabile <cmirabil@...hat.com>
Cc: linux-kernel@...r.kernel.org,
Peter Robinson <pbrobinson@...il.com>,
Serge Schneider <serge@...pberrypi.org>,
Stefan Wahren <stefan.wahren@...e.com>,
Nicolas Saenz Julienne <nicolassaenzj@...il.com>,
Mattias Brugger <mbrugger@...e.com>,
linux-rpi-kernel@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org, rh-kdlp@...glegroups.com,
Miguel Ojeda <ojeda@...nel.org>,
Joel Savitz <jsavitz@...hat.com>
Subject: Re: [PATCH 2/5] drivers/auxdisplay: sensehat: Raspberry Pi Sense HAT
display driver
On Tue, Aug 23, 2022 at 01:41:55PM -0400, Charles Mirabile wrote:
> This patch adds the driver for the 8x8 RGB LED matrix display
> on the Sense HAT. It appears as a character device named sense-hat
> in /dev/. That special file is 192 bytes large and contains 64
> RGB triplets (3 bytes each) one for each pixel in row major order.
>
> Co-developed-by: Joel Savitz <jsavitz@...hat.com>
> Signed-off-by: Joel Savitz <jsavitz@...hat.com>
> Signed-off-by: Charles Mirabile <cmirabil@...hat.com>
> ---
> drivers/auxdisplay/Kconfig | 8 +
> drivers/auxdisplay/Makefile | 1 +
> drivers/auxdisplay/sensehat-display.c | 205 ++++++++++++++++++++++++++
> 3 files changed, 214 insertions(+)
> create mode 100644 drivers/auxdisplay/sensehat-display.c
>
> diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
> index 64012cda4d12..9bad1aade7a0 100644
> --- a/drivers/auxdisplay/Kconfig
> +++ b/drivers/auxdisplay/Kconfig
> @@ -203,6 +203,14 @@ config ARM_CHARLCD
> line and the Linux version on the second line, but that's
> still useful.
>
> +config SENSEHAT_DISPLAY
> + tristate "Raspberry Pi Sense HAT display driver"
> + depends on I2C
> + select MFD_SIMPLE_MFD_I2C
> + help
> + This is a driver for the Raspberry Pi Sensehat 8x8 RBG-LED matrix
> + you can access it as a misc device at /dev/sense-hat
> +
> menuconfig PARPORT_PANEL
> tristate "Parallel port LCD/Keypad Panel support"
> depends on PARPORT
> diff --git a/drivers/auxdisplay/Makefile b/drivers/auxdisplay/Makefile
> index 6968ed4d3f0a..30b2b7934046 100644
> --- a/drivers/auxdisplay/Makefile
> +++ b/drivers/auxdisplay/Makefile
> @@ -14,3 +14,4 @@ obj-$(CONFIG_HT16K33) += ht16k33.o
> obj-$(CONFIG_PARPORT_PANEL) += panel.o
> obj-$(CONFIG_LCD2S) += lcd2s.o
> obj-$(CONFIG_LINEDISP) += line-display.o
> +obj-$(CONFIG_SENSEHAT_DISPLAY) += sensehat-display.o
> diff --git a/drivers/auxdisplay/sensehat-display.c b/drivers/auxdisplay/sensehat-display.c
> new file mode 100644
> index 000000000000..08c0c4338f3e
> --- /dev/null
> +++ b/drivers/auxdisplay/sensehat-display.c
> @@ -0,0 +1,205 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Raspberry Pi Sense HAT 8x8 LED matrix display driver
> + * http://raspberrypi.org
> + *
> + * Copyright (C) 2015 Raspberry Pi
> + * Copyright (C) 2021 Charles Mirabile, Joel Savitz
> + *
> + * Original Author: Serge Schneider
> + * Revised for upstream Linux by: Charles Mirabile, Joel Savitz
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +#include <linux/delay.h>
> +#include <linux/init.h>
> +#include <linux/platform_device.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/miscdevice.h>
> +#include <linux/regmap.h>
> +#include <linux/property.h>
> +
> +#define DISPLAY_SMB_REG 0x00
> +#define RGB_555_MASK 0x1f
> +#define NUM_LEDS 8
> +#define NUM_CHANNELS 3
> +
> +struct sensehat_display {
> + struct platform_device *pdev;
> + struct miscdevice mdev;
> + struct mutex rw_mtx;
Calling this rw_mtx is misleading, since it is not a rw_mutex. We should
rename it to mtx.
> + u8 vmem[NUM_LEDS][NUM_LEDS][NUM_CHANNELS];
> + struct regmap *regmap;
> +};
> +
> +#define VMEM_SIZE sizeof_field(struct sensehat_display, vmem)
> +
> +
> +static int sensehat_update_display(struct sensehat_display *display)
> +{
> + int i, j, k, ret;
> + u8 buff[NUM_LEDS][NUM_CHANNELS][NUM_LEDS];
> +
> + for (i = 0; i < NUM_LEDS; ++i)
> + for (j = 0; j < NUM_LEDS; ++j)
> + for (k = 0; k < NUM_CHANNELS; ++k)
> + buff[i][k][j] =
> + display->vmem[i][j][k] & RGB_555_MASK;
> +
> + ret = regmap_bulk_write(display->regmap, DISPLAY_SMB_REG, buff,
> + VMEM_SIZE);
> + if (ret < 0)
> + dev_err(&display->pdev->dev,
> + "Update to 8x8 LED matrix display failed");
> + return ret;
> +}
> +
> +static loff_t sensehat_display_llseek(struct file *filp, loff_t offset,
> + int whence)
> +{
> + return fixed_size_llseek(filp, offset, whence, VMEM_SIZE);
> +}
> +
> +static ssize_t sensehat_display_read(struct file *filp, char __user *buf,
> + size_t count, loff_t *f_pos)
> +{
> + struct sensehat_display *sensehat_display =
> + container_of(filp->private_data, struct sensehat_display, mdev);
> + ssize_t ret = -EFAULT;
> +
> + if (*f_pos < 0 || *f_pos >= VMEM_SIZE)
> + return 0;
Maybe it should return -EINVAL?
> + count = min_t(size_t, count, VMEM_SIZE - *f_pos);
> +
> + if (mutex_lock_interruptible(&sensehat_display->rw_mtx))
> + return -ERESTARTSYS;
> + if (copy_to_user(buf, *f_pos + (u8 *)sensehat_display->vmem, count))
> + goto out;
> + *f_pos += count;
> + ret = count;
> +out:
> + mutex_unlock(&sensehat_display->rw_mtx);
> + return ret;
> +}
> +
> +static ssize_t sensehat_display_write(struct file *filp, const char __user *buf,
> + size_t count, loff_t *f_pos)
> +{
> + struct sensehat_display *sensehat_display =
> + container_of(filp->private_data, struct sensehat_display, mdev);
> + int ret = -EFAULT;
> +
> + if (*f_pos < 0 || *f_pos >= VMEM_SIZE)
> + return -EFBIG;
> + count = min_t(size_t, count, VMEM_SIZE - *f_pos);
> +
> + if (mutex_lock_interruptible(&sensehat_display->rw_mtx))
> + return -ERESTARTSYS;
> + if (copy_from_user(*f_pos + (u8 *)sensehat_display->vmem, buf, count))
> + goto out;
> + ret = sensehat_update_display(sensehat_display);
> + if (ret < 0) {
> + ret = -EIO;
> + goto out;
> + }
> + *f_pos += count;
> + ret = count;
> +out:
> + mutex_unlock(&sensehat_display->rw_mtx);
> + return ret;
> +}
> +
> +static const struct file_operations sensehat_display_fops = {
> + .owner = THIS_MODULE,
> + .llseek = sensehat_display_llseek,
> + .read = sensehat_display_read,
> + .write = sensehat_display_write,
> +};
> +
> +static int sensehat_display_probe(struct platform_device *pdev)
> +{
> + int ret;
> +
> + struct sensehat_display *sensehat_display =
> + devm_kmalloc(&pdev->dev, sizeof(*sensehat_display), GFP_KERNEL);
> + if (!sensehat_display)
> + return -ENOMEM;
> +
> + sensehat_display->pdev = pdev;
> +
> + dev_set_drvdata(&pdev->dev, sensehat_display);
> +
> + sensehat_display->regmap = dev_get_regmap(pdev->dev.parent, NULL);
> + if (!sensehat_display->regmap) {
> + dev_err(&pdev->dev,
> + "unable to get sensehat regmap");
> + return -ENODEV;
> + }
> +
> + memset(sensehat_display->vmem, 0, VMEM_SIZE);
> +
> + mutex_init(&sensehat_display->rw_mtx);
> +
> + ret = sensehat_update_display(sensehat_display);
> + if (ret < 0) {
> + dev_err(&pdev->dev,
> + "Could not communicate with sensehat");
> + return ret;
> + }
> +
> + sensehat_display->mdev = (struct miscdevice){
> + .minor = MISC_DYNAMIC_MINOR,
> + .name = "sense-hat",
> + .mode = 0666,
> + .fops = &sensehat_display_fops,
> + };
> +
> + ret = misc_register(&sensehat_display->mdev);
> + if (ret < 0) {
> + dev_err(&pdev->dev,
> + "Could not register 8x8 LED matrix display.");
> + return ret;
> + }
> +
> + dev_info(&pdev->dev,
> + "8x8 LED matrix display registered with minor number %i",
> + sensehat_display->mdev.minor);
> +
> + return 0;
> +}
> +
> +static int sensehat_display_remove(struct platform_device *pdev)
> +{
> + struct sensehat_display *sensehat_display = dev_get_drvdata(&pdev->dev);
> +
> + misc_deregister(&sensehat_display->mdev);
> + return 0;
> +}
> +
> +static const struct of_device_id sensehat_display_device_id[] = {
> + { .compatible = "raspberrypi,sensehat-display" },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, sensehat_display_device_id);
> +
> +static struct platform_driver sensehat_display_driver = {
> + .probe = sensehat_display_probe,
> + .remove = sensehat_display_remove,
> + .driver = {
> + .name = "sensehat-display",
> + .of_match_table = sensehat_display_device_id,
> + },
> +};
> +
> +module_platform_driver(sensehat_display_driver);
> +
> +MODULE_DESCRIPTION("Raspberry Pi Sense HAT 8x8 LED matrix display driver");
> +MODULE_AUTHOR("Charles Mirabile <cmirabil@...hat.com>");
> +MODULE_AUTHOR("Serge Schneider <serge@...pberrypi.org>");
> +MODULE_LICENSE("GPL");
> --
> 2.31.1
>
>
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