kernel: pseudodevices (null, full and zero)

kernel-src/arch/x86-64/main.c

@@ -18,6 +18,7 @@
 #include <kernel/tmpfs.h>
 #include <kernel/initrd.h>
 #include <kernel/devfs.h>
+#include <kernel/pseudodevices.h>
 
 static cpu_t bsp_cpu;
 
@@ -55,5 +56,7 @@ void kernel_entry() {
 	printf("mounting devfs on /dev\n");
 	__assert(vfs_mount(NULL, vfsroot, "/dev", "devfs", NULL) == 0);
 
+	pseudodevices_init();
+
 	__assert(!"kernel entry end");
 }

kernel-src/include/kernel/devfs.h

@@ -3,6 +3,10 @@
 
 #include <kernel/vfs.h>
 
+#define DEV_MAJOR_NULL 1
+#define DEV_MAJOR_FULL 2
+#define DEV_MAJOR_ZERO 3
+
 typedef struct {
 	int (*open)(int minor, int flags);
 	int (*close)(int minor, int flags);

kernel-src/include/kernel/pseudodevices.h

@@ -0,0 +1,6 @@
+#ifndef _PSEUDODEVICES_H
+#define _PSEUDODEVICES_H
+
+void pseudodevices_init();
+
+#endif

kernel-src/io/pseudodevices.c

@@ -0,0 +1,45 @@
+#include <kernel/devfs.h>
+#include <errno.h>
+#include <string.h>
+#include <logging.h>
+
+static int null_write(int minor, void *buffer, size_t count, uintmax_t offset, int flags, size_t *wcount) {
+	*wcount = count;
+	return 0;
+}
+
+static int full_write(int minor, void *buffer, size_t count, uintmax_t offset, int flags, size_t *wcount) {
+	return ENOSPC;
+}
+
+static int zero_read(int minor, void *buffer, size_t count, uintmax_t offset, int flags, size_t *rcount) {
+	*rcount = count;
+	memset(buffer, 0, count);
+	return 0;
+}
+
+static int null_read(int minor, void *buffer, size_t count, uintmax_t offset, int flags, size_t *rcount) {
+	*rcount = 0;
+	return 0;
+}
+
+static devops_t nullops = {
+	.read = null_read,
+	.write = null_write
+};
+
+static devops_t fullops = {
+	.read = zero_read,
+	.write = full_write
+};
+
+static devops_t zeroops = {
+	.read = zero_read,
+	.write = null_write
+};
+
+void pseudodevices_init() {
+	__assert(devfs_register(&nullops, "null", V_TYPE_CHDEV, DEV_MAJOR_NULL, 0, 0644) == 0);
+	__assert(devfs_register(&fullops, "full", V_TYPE_CHDEV, DEV_MAJOR_FULL, 0, 0644) == 0);
+	__assert(devfs_register(&zeroops, "zero", V_TYPE_CHDEV, DEV_MAJOR_ZERO, 0, 0644) == 0);
+}