[PATCH v8 3/6] drivers/auxdisplay: sensehat: Raspberry Pi Sense HAT display driver

From: Charles Mirabile
Date: Tue Apr 12 2022 - 16:20:02 EST


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 128 bytes large and contains 64
RGB565 triples (2 bytes each) one for each pixel.

Co-developed-by: Daniel Bauman <dbauman@xxxxxxxxxx>
Signed-off-by: Daniel Bauman <dbauman@xxxxxxxxxx>
Co-developed-by: Mwesigwa Guma <mguma@xxxxxxxxxx>
Signed-off-by: Mwesigwa Guma <mguma@xxxxxxxxxx>
Co-developed-by: Joel Savitz <jsavitz@xxxxxxxxxx>
Signed-off-by: Joel Savitz <jsavitz@xxxxxxxxxx>
Signed-off-by: Charles Mirabile <cmirabil@xxxxxxxxxx>
---
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..9faaee5cde8a
--- /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, Mwesigwa Guma, Joel Savitz
+ *
+ * Original Author: Serge Schneider
+ * Revised for upstream Linux by: Charles Mirabile, Mwesigwa Guma, 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;
+ 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;
+ 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@xxxxxxxxxx>");
+MODULE_AUTHOR("Serge Schneider <serge@xxxxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL");
--
2.31.1