arch/v850/kernel/rte_cb_leds.c

   1 /*
   2  * include/asm-v850/rte_cb_leds.c -- Midas lab RTE-CB board LED device support
   3  *
   4  *  Copyright (C) 2002,03  NEC Electronics Corporation
   5  *  Copyright (C) 2002,03  Miles Bader <miles@gnu.org>
   6  *
   7  * This file is subject to the terms and conditions of the GNU General
   8  * Public License.  See the file COPYING in the main directory of this
   9  * archive for more details.
  10  *
  11  * Written by Miles Bader <miles@gnu.org>
  12  */
  13
  14 #include <linux/init.h>
  15 #include <linux/spinlock.h>
  16 #include <linux/fs.h>
  17 #include <linux/miscdevice.h>
  18
  19 #include <asm/uaccess.h>
  20
  21 #define LEDS_MINOR      169     /* Minor device number, using misc major.  */
  22
  23 /* The actual LED hardware is write-only, so we hold the contents here too.  */
  24 static unsigned char leds_image[LED_NUM_DIGITS] = { 0 };
  25
  26 /* Spinlock protecting the above leds.  */
  27 static DEFINE_SPINLOCK(leds_lock);
  28
  29 /* Common body of LED read/write functions, checks POS and LEN for
  30    correctness, declares a variable using IMG_DECL, initialized pointing at
  31    the POS position in the LED image buffer, and and iterates COPY_EXPR
  32    until BUF is equal to the last buffer position; finally, sets LEN to be
  33    the amount actually copied.  IMG should be a variable declaration
  34    (without an initializer or a terminating semicolon); POS, BUF, and LEN
  35    should all be simple variables.  */
  36 #define DO_LED_COPY(img_decl, pos, buf, len, copy_expr)                 \
  37 do {                                                                    \
  38         if (pos > LED_NUM_DIGITS)                                       \
  39                 len = 0;                                                \
  40         else {                                                          \
  41                 if (pos + len > LED_NUM_DIGITS)                         \
  42                         len = LED_NUM_DIGITS - pos;                     \
  43                                                                         \
  44                 if (len > 0) {                                          \
  45                         unsigned long _flags;                           \
  46                         const char *_end = buf + len;                   \
  47                         img_decl = &leds_image[pos];                    \
  48                                                                         \
  49                         spin_lock_irqsave (leds_lock, _flags);          \
  50                         do                                              \
  51                                 (copy_expr);                            \
  52                         while (buf != _end);                            \
  53                         spin_unlock_irqrestore (leds_lock, _flags);     \
  54                 }                                                       \
  55         }                                                               \
  56 } while (0)
  57
  58 /* Read LEN bytes from LEDs at position POS, into BUF.
  59    Returns actual amount read.  */
  60 unsigned read_leds (unsigned pos, char *buf, unsigned len)
  61 {
  62         DO_LED_COPY (const char *img, pos, buf, len, *buf++ = *img++);
  63         return len;
  64 }
  65
  66 /* Write LEN bytes to LEDs at position POS, from BUF.
  67    Returns actual amount written.  */
  68 unsigned write_leds (unsigned pos, const char *buf, unsigned len)
  69 {
  70         /* We write the actual LED values backwards, because
  71            increasing memory addresses reflect LEDs right-to-left. */
  72         volatile char *led = &LED (LED_NUM_DIGITS - pos - 1);
  73         /* We invert the value written to the hardware, because 1 = off,
  74            and 0 = on.  */
  75         DO_LED_COPY (char *img, pos, buf, len,
  76                      *led-- = 0xFF ^ (*img++ = *buf++));
  77         return len;
  78 }
  79
  80 \f
  81 /* Device functions.  */
  82
  83 static ssize_t leds_dev_read (struct file *file, char *buf, size_t len,
  84                               loff_t *pos)
  85 {
  86         char temp_buf[LED_NUM_DIGITS];
  87         len = read_leds (*pos, temp_buf, len);
  88         if (copy_to_user (buf, temp_buf, len))
  89                 return -EFAULT;
  90         *pos += len;
  91         return len;
  92 }
  93
  94 static ssize_t leds_dev_write (struct file *file, const char *buf, size_t len,
  95                                loff_t *pos)
  96 {
  97         char temp_buf[LED_NUM_DIGITS];
  98         if (copy_from_user (temp_buf, buf, min_t(size_t, len, LED_NUM_DIGITS)))
  99                 return -EFAULT;
 100         len = write_leds (*pos, temp_buf, len);
 101         *pos += len;
 102         return len;
 103 }
 104
 105 static loff_t leds_dev_lseek (struct file *file, loff_t offs, int whence)
 106 {
 107         if (whence == 1)
 108                 offs += file->f_pos; /* relative */
 109         else if (whence == 2)
 110                 offs += LED_NUM_DIGITS; /* end-relative */
 111
 112         if (offs < 0 || offs > LED_NUM_DIGITS)
 113                 return -EINVAL;
 114
 115         file->f_pos = offs;
 116
 117         return 0;
 118 }
 119
 120 static const struct file_operations leds_fops = {
 121         .read           = leds_dev_read,
 122         .write          = leds_dev_write,
 123         .llseek         = leds_dev_lseek
 124 };
 125
 126 static struct miscdevice leds_miscdev = {
 127         .name           = "leds",
 128         .minor          = LEDS_MINOR,
 129         .fops           = &leds_fops
 130 };
 131
 132 int __init leds_dev_init (void)
 133 {
 134         return misc_register (&leds_miscdev);
 135 }
 136
 137 __initcall (leds_dev_init);