From 1a8a5e5f7ec151c38eec7b4d0ca4835fc717e010 Mon Sep 17 00:00:00 2001
From: Marcin Chrzanowski <marcin.j.chrzanowski@gmail.com>
Date: Wed, 16 May 2018 11:19:13 +0200
Subject: Create scaffold surface

---
 surface.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 75 insertions(+), 1 deletion(-)

diff --git a/surface.c b/surface.c
index 3c24871..8400e3f 100644
--- a/surface.c
+++ b/surface.c
@@ -1,8 +1,82 @@
+#include <linux/anon_inodes.h>
+#include <linux/file.h>
 #include <linux/fs.h>
 
 #include "surface.h"
 
-int new_surface(struct doomdev_ioctl_create_surface *params)
+long surface_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	return -1;
 }
+
+ssize_t surface_read(struct file *filp, char __user *buf, size_t count,
+		loff_t *offset)
+{
+	return -1;
+}
+
+loff_t surface_llseek(struct file *filp, loff_t offset, int origin)
+{
+	return -1;
+}
+
+struct file_operations surface_fops = {
+	.owner = THIS_MODULE,
+	.unlocked_ioctl = surface_ioctl,
+	.compat_ioctl = surface_ioctl,
+	.llseek = surface_llseek,
+	.read = surface_read
+};
+
+int verify_params(struct doomdev_ioctl_create_surface *params)
+{
+	if (params->width < 64) {
+		printk(KERN_DEBUG "Surface width too small\n");
+		return -EINVAL;
+	}
+
+	if (params->width > 2048) {
+		printk(KERN_DEBUG "Surface width too large\n");
+		return -EOVERFLOW;
+	}
+
+	if (params->width % 64 != 0) {
+		printk(KERN_DEBUG "Surface width not a multiple of 64\n");
+		return -EINVAL;
+	}
+
+	if (params->height < 1) {
+		printk(KERN_DEBUG "Surface height too small\n");
+		return -EINVAL;
+	}
+
+	if (params->height > 2048) {
+		printk(KERN_DEBUG "Surface height too large\n");
+		return -EOVERFLOW;
+	}
+
+	return 0;
+}
+
+int new_surface(struct doomdev_ioctl_create_surface *params)
+{
+	int err;
+	int fd;
+	struct fd fd_s;
+
+	err = verify_params(params);
+	if (err < 0) {
+		return err;
+	}
+
+	fd = anon_inode_getfd("doom_surface", &surface_fops, NULL, 0);
+	fd_s = fdget(fd);
+	if (fd_s.file->f_op != &surface_fops) {
+		printk(KERN_DEBUG "fdget failed\n");
+		return -ENOENT;
+	}
+
+	fd_s.file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
+
+	return fd;
+}
-- 
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