devsynth.c

Go to the documentation of this file.

#include <linux/errno.h>
#include <linux/miscdevice.h>   /* for misc_register, and SYNTH_MINOR */
#include <linux/types.h>
#include <linux/uaccess.h>

#include "speakup.h"
#include "spk_priv.h"

#ifndef SYNTH_MINOR
#define SYNTH_MINOR 25
#endif

static int misc_registered;
static int dev_opened;

static ssize_t speakup_file_write(struct file *fp, const char *buffer,
           size_t nbytes, loff_t *ppos)
{
    size_t count = nbytes;
    const char *ptr = buffer;
    size_t bytes;
    unsigned long flags;
    u_char buf[256];

    if (synth == NULL)
        return -ENODEV;
    while (count > 0) {
        bytes = min(count, sizeof(buf));
        if (copy_from_user(buf, ptr, bytes))
            return -EFAULT;
        count -= bytes;
        ptr += bytes;
        spk_lock(flags);
        synth_write(buf, bytes);
        spk_unlock(flags);
    }
    return (ssize_t) nbytes;
}

static ssize_t speakup_file_read(struct file *fp, char *buf, size_t nbytes,
    loff_t *ppos)
{
    return 0;
}

static int speakup_file_open(struct inode *ip, struct file *fp)
{
    if (synth == NULL)
        return -ENODEV;
    if (xchg(&dev_opened, 1))
        return -EBUSY;
    return 0;
}

static int speakup_file_release(struct inode *ip, struct file *fp)
{
    dev_opened = 0;
    return 0;
}

static const struct file_operations synth_fops = {
    .read = speakup_file_read,
    .write = speakup_file_write,
    .open = speakup_file_open,
    .release = speakup_file_release,
};

static struct miscdevice synth_device = {
    .minor = SYNTH_MINOR,
    .name = "synth",
    .fops = &synth_fops,
};

void speakup_register_devsynth(void)
{
    if (misc_registered != 0)
        return;
/* zero it so if register fails, deregister will not ref invalid ptrs */
    if (misc_register(&synth_device))
        pr_warn("Couldn't initialize miscdevice /dev/synth.\n");
    else {
        pr_info("initialized device: /dev/synth, node (MAJOR %d, MINOR %d)\n",
            MISC_MAJOR, SYNTH_MINOR);
        misc_registered = 1;
    }
}

void speakup_unregister_devsynth(void)
{
    if (!misc_registered)
        return;
    pr_info("speakup: unregistering synth device /dev/synth\n");
    misc_deregister(&synth_device);
    misc_registered = 0;
}