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kernel_dev.c
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kernel_dev.c
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#include <assert.h>
#include "kernel_cc.h"
#include "kernel_dev.h"
#include "kernel_sched.h"
#include "kernel_streams.h"
#include "kernel_proc.h"
/*************************************
Devices and device drivers
*************************************/
DCB DT[MAX_TERMINALS];
/* ===================================
The null device driver
====================================*/
int nulldev_read(void* dev, char *buf, unsigned int size)
{
memset(buf, 0, size);
return size;
}
int nulldev_write(void* dev, const char* buf, unsigned int size)
{
/* Here, we do not copy anything, therefore simply return
a value equal to the argument.
*/
return size;
}
int nulldev_close(void* dev)
{
return 0;
}
void* nulldev_open(uint minor)
{
return NULL;
}
static file_ops nulldev_fops = {
.Open = nulldev_open,
.Read = nulldev_read,
.Write = nulldev_write,
.Close = nulldev_close
};
/*============================================
The serial device driver
============================================*/
/* forward */
void serial_rx_handler();
void serial_tx_handler();
typedef struct serial_device_control_block {
uint devno;
Mutex spinlock;
CondVar rx_ready;
} serial_dcb_t;
serial_dcb_t serial_dcb[MAX_TERMINALS];
/*
Interrupt-driven driver for serial-device reads.
*/
void serial_rx_handler()
{
int pre = preempt_off;
/*
We do not know which terminal is
ready, so we must signal them all !
*/
for(int i=0;i<bios_serial_ports();i++) {
serial_dcb_t* dcb = &serial_dcb[i];
Cond_Broadcast(&dcb->rx_ready);
}
if(pre) preempt_on;
}
/*
Read from the device, sleeping if needed.
*/
int serial_read(void* dev, char *buf, unsigned int size)
{
serial_dcb_t* dcb = (serial_dcb_t*)dev;
preempt_off; /* Stop preemption */
uint count = 0;
while(count<size) {
int valid = bios_read_serial(dcb->devno, &buf[count]);
if (valid) {
count++;
}
else if(count==0) {
kernel_wait(&dcb->rx_ready, SCHED_IO);
}
else
break;
}
preempt_on; /* Restart preemption */
return count;
}
/*
A polling driver for serial writes
*/
/* Interrupt driver */
void serial_tx_handler()
{
/* There is nothing to do */
}
/*
Write call
This is currently a polling driver.
*/
int serial_write(void* dev, const char* buf, unsigned int size)
{
serial_dcb_t* dcb = (serial_dcb_t*)dev;
unsigned int count = 0;
while(count < size) {
int success = bios_write_serial(dcb->devno, buf[count] );
if(success) {
count++;
}
else if(count==0)
{
yield(SCHED_IO);
}
else
break;
}
return count;
}
int serial_close(void* dev)
{
return 0;
}
void* serial_open(uint term)
{
assert(term<bios_serial_ports());
return & serial_dcb[term];
}
file_ops serial_fops = {
.Open = serial_open,
.Read = serial_read,
.Write = serial_write,
.Close = serial_close
};
/***********************************
The device table
***********************************/
DCB devtable[DEV_MAX];
void initialize_devices()
{
devtable[DEV_NULL].type = DEV_NULL;
devtable[DEV_NULL].devnum = 1;
devtable[DEV_NULL].dev_fops = nulldev_fops;
devtable[DEV_SERIAL].type = DEV_SERIAL;
devtable[DEV_SERIAL].devnum = bios_serial_ports();
devtable[DEV_SERIAL].dev_fops = serial_fops;
/* Initialize the serial devices */
for(int i=0; i<bios_serial_ports(); i++) {
serial_dcb[i].devno = i;
serial_dcb[i].rx_ready = COND_INIT;
serial_dcb[i].spinlock = MUTEX_INIT;
}
cpu_interrupt_handler(SERIAL_RX_READY, serial_rx_handler);
cpu_interrupt_handler(SERIAL_TX_READY, serial_tx_handler);
}
int device_open(Device_type major, uint minor, void** obj, file_ops** ops)
{
assert(major < DEV_MAX);
if(minor >= devtable[major].devnum)
return -1;
*obj = devtable[major].dev_fops.Open(minor);
*ops = &devtable[major].dev_fops;
return 0;
}
uint device_no(Device_type major)
{
return devtable[major].devnum;
}