[PATCH linux v1 2/4] drivers: misc: Character device driver for seven segment display
Jaghathiswari Rankappagounder Natarajan
jaghu at google.com
Wed Dec 14 18:55:02 AEDT 2016
Character device driver which implements the user-space
API for letting a user write to two 7-segment displays including
any conversion methods necessary to map the user input
to two 7-segment displays.
Signed-off-by: Jaghathiswari Rankappagounder Natarajan <jaghu at google.com>
---
drivers/misc/Kconfig | 8 ++
drivers/misc/Makefile | 1 +
drivers/misc/seven_seg_disp.c | 197 ++++++++++++++++++++++++++++++++++++++++++
drivers/misc/seven_seg_disp.h | 34 ++++++++
4 files changed, 240 insertions(+)
create mode 100644 drivers/misc/seven_seg_disp.c
create mode 100644 drivers/misc/seven_seg_disp.h
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index a216b46..a21aec1 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -791,6 +791,14 @@ config PANEL_CHANGE_MESSAGE
If you say 'Y' here, you'll be able to choose a message yourself. Otherwise,
say 'N' and keep the default message with the version.
+config SEVEN_SEGMENT_DISPLAY
+ tristate "Character driver for seven segment display support"
+ help
+ Character device driver which implements the user-space
+ API for letting a user write to two 7-segment displays including
+ any conversion methods necessary to map the user input
+ to two 7-segment displays.
+
config PANEL_BOOT_MESSAGE
depends on PANEL && PANEL_CHANGE_MESSAGE="y"
string "New initialization message"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index b2fb6dbf..c2defbd 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -56,4 +56,5 @@ obj-$(CONFIG_GENWQE) += genwqe/
obj-$(CONFIG_ECHO) += echo/
obj-$(CONFIG_VEXPRESS_SYSCFG) += vexpress-syscfg.o
obj-$(CONFIG_CXL_BASE) += cxl/
+obj-$(CONFIG_SEVEN_SEGMENT_DISPLAY) += seven_seg_disp.o
obj-$(CONFIG_PANEL) += panel.o
diff --git a/drivers/misc/seven_seg_disp.c b/drivers/misc/seven_seg_disp.c
new file mode 100644
index 0000000..4daeac5
--- /dev/null
+++ b/drivers/misc/seven_seg_disp.c
@@ -0,0 +1,197 @@
+/*
+ * Copyright (c) 2016 Google, Inc
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 or later as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/version.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/kdev_t.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/ctype.h>
+#include <linux/of.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/platform_device.h>
+
+#include "seven_seg_disp.h"
+
+#define LED_DOT 0x01
+
+/*
+ * 0 1 2 3 4 5 6 7 8 9 A B C D E F
+ * _ _ _ _ _ _ _ _ _ _ _ _
+ * | | | _| _| |_| |_ |_ | |_| |_| |_| |_ | _| |_ |_
+ * |_| | |_ _| | _| |_| | |_| | | | |_| |_ |_| |_ |
+ *
+ * data[7:1] = led[a:g]
+ */
+const u8 seven_seg_bits[] = {
+ 0xFC, 0x60, 0xDA, 0xF2, 0x66, 0xB6, 0xBE, 0xE0,
+ 0xFE, 0xF6, 0xEE, 0x3E, 0x9C, 0x7A, 0x9E, 0x8E
+ };
+
+/*
+ * 0 1 2 3 4 5 6 7 8 9 A B C D E F
+ * _ _ _ _ _
+ * | |_ |_| |_ _ _ _ _ _ _ _ |_ _| _| | |
+ * |_ |_ | | _| |_| |_| | |
+ *
+ * data[7:1] = led[a:g]
+ */
+const u8 special_seven_seg_bits[] = {
+ 0x00, 0x9C, 0x1E, 0xCE, 0x8E, 0x02, 0x02, 0x02,
+ 0x02, 0x02, 0x02, 0x02, 0xB6, 0x7A, 0x7A, 0xEC
+ };
+
+static dev_t seven_seg_devno;
+static struct class *seven_seg_disp_class;
+
+static int seven_seg_disp_open(struct inode *inode, struct file *filp)
+{
+ struct seven_seg_disp_dev *disp_dev;
+
+ disp_dev = container_of(inode->i_cdev,
+ struct seven_seg_disp_dev, cdev);
+ filp->private_data = disp_dev;
+ return 0;
+}
+
+static int seven_seg_disp_close(struct inode *inode, struct file *filp)
+{
+ filp->private_data = NULL;
+ return 0;
+}
+
+static ssize_t seven_seg_disp_read(struct file *filp, char __user *buf, size_t
+ len, loff_t *off)
+{
+ struct seven_seg_disp_dev *disp_dev = filp->private_data;
+
+ if (disp_dev->disp_data_valid)
+ return -EINVAL;
+
+ if (copy_to_user(buf, disp_dev->seven_seg_disp_data_array,
+ MAX_DISP_CHAR_SIZE) != 0) {
+ return -EFAULT;
+ }
+
+ return 0;
+}
+
+static u16 convert_to_disp_data(char *buf)
+{
+ u8 low_display;
+ u8 high_display;
+ u16 led_value;
+
+ low_display = seven_seg_bits[hex_to_bin(buf[2])];
+
+ high_display = (buf[0] == '1') ?
+ special_seven_seg_bits[hex_to_bin(buf[1])] :
+ seven_seg_bits[hex_to_bin(buf[1])];
+
+ led_value = low_display | (high_display << 8);
+ if (buf[0] == '1')
+ led_value |= LED_DOT | (LED_DOT << 8);
+
+ return led_value;
+}
+
+static ssize_t seven_seg_disp_write(struct file *filp, const char __user *buf,
+ size_t len, loff_t *off)
+{
+ int length = len - 1;
+ int i;
+
+ struct seven_seg_disp_dev *disp_dev = filp->private_data;
+
+ if (length != MAX_DISP_CHAR_SIZE)
+ return -EINVAL;
+
+ if (copy_from_user(disp_dev->seven_seg_disp_data_array,
+ buf, length) != 0) {
+ return -EFAULT;
+ }
+
+ for (i = 0; i < MAX_DISP_CHAR_SIZE; i++) {
+ if (!isxdigit(disp_dev->seven_seg_disp_data_array[i]))
+ return -EINVAL;
+ }
+
+ disp_dev->current_seven_seg_disp_data = convert_to_disp_data(
+ disp_dev->seven_seg_disp_data_array);
+ disp_dev->disp_data_valid = true;
+ disp_dev->update_seven_seg_data(&disp_dev->parent,
+ disp_dev->current_seven_seg_disp_data);
+
+ return len;
+}
+
+static const struct file_operations seven_seg_disp_fops = {
+
+ .owner = THIS_MODULE,
+ .open = seven_seg_disp_open,
+ .release = seven_seg_disp_close,
+ .read = seven_seg_disp_read,
+ .write = seven_seg_disp_write
+};
+
+void seven_seg_rem_cdev(struct seven_seg_disp_dev *disp_dev)
+{
+ cdev_del(&disp_dev->cdev);
+ device_destroy(seven_seg_disp_class, seven_seg_devno);
+}
+
+int seven_seg_setup_cdev(struct seven_seg_disp_dev *disp_dev,
+ void (*update_disp_data)(struct device *, u16 data))
+{
+ struct device *dev;
+ int err;
+
+ dev = device_create(seven_seg_disp_class, &disp_dev->parent,
+ seven_seg_devno,
+ NULL, "seven_seg_disp_val");
+ if (dev == NULL)
+ return -1;
+ disp_dev->dev = dev;
+ disp_dev->update_seven_seg_data = update_disp_data;
+ disp_dev->disp_data_valid = false;
+
+ cdev_init(&disp_dev->cdev, &seven_seg_disp_fops);
+ err = cdev_add(&disp_dev->cdev, seven_seg_devno, 1);
+ if (err)
+ device_destroy(seven_seg_disp_class, seven_seg_devno);
+ return err;
+}
+
+static int __init seven_seg_disp_init(void)
+{
+ if (alloc_chrdev_region(&seven_seg_devno, 0, 1, "disp_state") < 0)
+ return -1;
+
+ seven_seg_disp_class = class_create(THIS_MODULE, "disp_state");
+ if (seven_seg_disp_class == NULL)
+ goto unreg_chrdev;
+
+unreg_chrdev:
+ unregister_chrdev_region(seven_seg_devno, 1);
+ return -1;
+}
+
+static void __exit seven_seg_disp_exit(void)
+{
+ class_destroy(seven_seg_disp_class);
+ unregister_chrdev_region(seven_seg_devno, 1);
+}
+
+module_init(seven_seg_disp_init);
+module_exit(seven_seg_disp_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jaghathiswari Rankappagounder Natarajan <jaghu at google.com>");
+MODULE_DESCRIPTION("Seven segment display character driver");
diff --git a/drivers/misc/seven_seg_disp.h b/drivers/misc/seven_seg_disp.h
new file mode 100644
index 0000000..b0f93c5
--- /dev/null
+++ b/drivers/misc/seven_seg_disp.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2016 Google, Inc
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 or later as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef SEVEN_SEG_DISP_H
+#define SEVEN_SEG_DISP_H
+
+#include <linux/device.h>
+#include <linux/cdev.h>
+
+#define MAX_DISP_CHAR_SIZE 3
+
+#define DEFAULT_REFRESH_INTERVAL_MS 1000
+
+struct seven_seg_disp_dev {
+ bool disp_data_valid;
+ u16 current_seven_seg_disp_data;
+ char seven_seg_disp_data_array[MAX_DISP_CHAR_SIZE];
+ struct device parent;
+ struct device *dev;
+ struct cdev cdev;
+ void (*update_seven_seg_data)(struct device *, u16 data);
+};
+
+int seven_seg_setup_cdev(struct seven_seg_disp_dev *disp_dev,
+ void (*update_disp_data)(struct device *, u16 data));
+
+void seven_seg_rem_cdev(struct seven_seg_disp_dev *disp_dev);
+
+#endif
--
2.8.0.rc3.226.g39d4020
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