《操作系统》的实验代码。
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#include <defs.h>
#include <string.h>
#include <stat.h>
#include <dev.h>
#include <inode.h>
#include <unistd.h>
#include <error.h>
/*
* dev_open - Called for each open().
*/
static int
dev_open(struct inode *node, uint32_t open_flags) {
if (open_flags & (O_CREAT | O_TRUNC | O_EXCL | O_APPEND)) {
return -E_INVAL;
}
struct device *dev = vop_info(node, device);
return dop_open(dev, open_flags);
}
/*
* dev_close - Called on the last close(). Just pass through.
*/
static int
dev_close(struct inode *node) {
struct device *dev = vop_info(node, device);
return dop_close(dev);
}
/*
* dev_read -Called for read. Hand off to iobuf.
*/
static int
dev_read(struct inode *node, struct iobuf *iob) {
struct device *dev = vop_info(node, device);
return dop_io(dev, iob, 0);
}
/*
* dev_write -Called for write. Hand off to iobuf.
*/
static int
dev_write(struct inode *node, struct iobuf *iob) {
struct device *dev = vop_info(node, device);
return dop_io(dev, iob, 1);
}
/*
* dev_ioctl - Called for ioctl(). Just pass through.
*/
static int
dev_ioctl(struct inode *node, int op, void *data) {
struct device *dev = vop_info(node, device);
return dop_ioctl(dev, op, data);
}
/*
* dev_fstat - Called for stat().
* Set the type and the size (block devices only).
* The link count for a device is always 1.
*/
static int
dev_fstat(struct inode *node, struct stat *stat) {
int ret;
memset(stat, 0, sizeof(struct stat));
if ((ret = vop_gettype(node, &(stat->st_mode))) != 0) {
return ret;
}
struct device *dev = vop_info(node, device);
stat->st_nlinks = 1;
stat->st_blocks = dev->d_blocks;
stat->st_size = stat->st_blocks * dev->d_blocksize;
return 0;
}
/*
* dev_gettype - Return the type. A device is a "block device" if it has a known
* length. A device that generates data in a stream is a "character
* device".
*/
static int
dev_gettype(struct inode *node, uint32_t *type_store) {
struct device *dev = vop_info(node, device);
*type_store = (dev->d_blocks > 0) ? S_IFBLK : S_IFCHR;
return 0;
}
/*
* dev_tryseek - Attempt a seek.
* For block devices, require block alignment.
* For character devices, prohibit seeking entirely.
*/
static int
dev_tryseek(struct inode *node, off_t pos) {
struct device *dev = vop_info(node, device);
if (dev->d_blocks > 0) {
if ((pos % dev->d_blocksize) == 0) {
if (pos >= 0 && pos < dev->d_blocks * dev->d_blocksize) {
return 0;
}
}
}
return -E_INVAL;
}
/*
* dev_lookup - Name lookup.
*
* One interesting feature of device:name pathname syntax is that you
* can implement pathnames on arbitrary devices. For instance, if you
* had a graphics device that supported multiple resolutions (which we
* don't), you might arrange things so that you could open it with
* pathnames like "video:800x600/24bpp" in order to select the operating
* mode.
*
* However, we have no support for this in the base system.
*/
static int
dev_lookup(struct inode *node, char *path, struct inode **node_store) {
if (*path != '\0') {
return -E_NOENT;
}
vop_ref_inc(node);
*node_store = node;
return 0;
}
/*
* Function table for device inodes.
*/
static const struct inode_ops dev_node_ops = {
.vop_magic = VOP_MAGIC,
.vop_open = dev_open,
.vop_close = dev_close,
.vop_read = dev_read,
.vop_write = dev_write,
.vop_fstat = dev_fstat,
.vop_ioctl = dev_ioctl,
.vop_gettype = dev_gettype,
.vop_tryseek = dev_tryseek,
.vop_lookup = dev_lookup,
};
#define init_device(x) \
do { \
extern void dev_init_##x(void); \
dev_init_##x(); \
} while (0)
/* dev_init - Initialization functions for builtin vfs-level devices. */
void
dev_init(void) {
// init_device(null);
init_device(stdin);
init_device(stdout);
init_device(disk0);
}
/* dev_create_inode - Create inode for a vfs-level device. */
struct inode *
dev_create_inode(void) {
struct inode *node;
if ((node = alloc_inode(device)) != NULL) {
vop_init(node, &dev_node_ops, NULL);
}
return node;
}