framebuffer: initial implementation

src/arch/x86_64/main.c

@@ -64,6 +64,8 @@ void kmain(){
 	consoledev_init();
 
 	pseudodevs_init();
+	
+	fb_init();
 
 	pci_enumerate();
 

src/video/framebuffer.c

@@ -0,0 +1,91 @@
+#include <kernel/devman.h>
+#include <limine.h>
+#include <string.h>
+#include <errno.h>
+
+static volatile struct limine_framebuffer_request fbreq = {
+	.id = LIMINE_FRAMEBUFFER_REQUEST,
+	.revision = 0
+};
+
+static struct limine_framebuffer** fbs;
+static size_t fbcount;
+
+static int devchecks(int fb, size_t* count, size_t offset){
+	
+	if(fb >= fbcount)
+		return ENODEV;
+
+	size_t end = fbs[fb]->pitch * fbs[fb]->height;
+
+	if(*count + offset > end)
+		*count = end - offset;
+
+	return 0;
+	
+
+}
+
+int read(int* error, int minor, void* buff, size_t count, size_t offset){
+
+	*error = devchecks(minor, &count, offset);
+
+	if(*error)
+		return -1;
+	
+	memcpy(buff, fbs[minor]->address + offset, count);
+	
+	return count;
+	
+}
+
+int write(int* error, int minor, void* buff, size_t count, size_t offset){
+	
+	*error = devchecks(minor, &count, offset);
+
+	if(*error)
+		return -1;
+	
+	memcpy(fbs[minor]->address + offset, buff, count);
+
+	return count;
+}
+
+int isatty(int minor){
+	return ENOTTY;
+}
+
+static int isseekable(int minor, size_t* max){
+        
+	if(minor >= fbcount)
+		return ENODEV;
+
+	*max = fbs[minor]->pitch * fbs[minor]->height;
+
+        return 0;
+}
+
+
+static devcalls calls = {
+	read, write, isatty, isseekable
+};
+
+void fb_init(){
+	
+	if(!fbreq.response)
+		return;
+	
+	fbcount = fbreq.response->framebuffer_count;
+	fbs = fbreq.response->framebuffers;
+	
+	char name[] = { 'f', 'b', '0', 0};
+
+	for(uintmax_t fb = 0; fb < fbcount; ++fb){
+		
+		devman_newdevice(name, TYPE_CHARDEV, MAJOR_FB, fb, &calls);
+
+		++name[2]; // increase the fbX num
+
+	}
+
+}