fs: implement flush function

Once we have caching in file functions we need a way to sync
the the underlying devices.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

fs/devfs.c

@@ -169,6 +169,16 @@ static int devfs_close(struct device_d *_dev, FILE *f)
 	return 0;
 }
 
+static int devfs_flush(struct device_d *_dev, FILE *f)
+{
+	struct cdev *cdev = f->inode;
+
+	if (cdev->ops->flush)
+		return cdev->ops->flush(cdev);
+
+	return 0;
+}
+
 static int partition_ioctl(struct cdev *cdev, int request, void *buf)
 {
 	size_t offset;
@@ -287,6 +297,7 @@ static struct fs_driver_d devfs_driver = {
 	.lseek     = devfs_lseek,
 	.open      = devfs_open,
 	.close     = devfs_close,
+	.flush     = devfs_flush,
 	.ioctl     = devfs_ioctl,
 	.opendir   = devfs_opendir,
 	.readdir   = devfs_readdir,

fs/fs.c

@@ -536,6 +536,26 @@ ssize_t write(int fd, const void *buf, size_t count)
 }
 EXPORT_SYMBOL(write);
 
+int flush(int fd)
+{
+	struct device_d *dev;
+	struct fs_driver_d *fsdrv;
+	FILE *f = &files[fd];
+
+	if (check_fd(fd))
+		return errno;
+
+	dev = f->dev;
+
+	fsdrv = (struct fs_driver_d *)dev->driver->type_data;
+	if (fsdrv->flush)
+		errno = fsdrv->flush(dev, f);
+	else
+		errno = 0;
+
+	return errno;
+}
+
 off_t lseek(int fildes, off_t offset, int whence)
 {
 	struct device_d *dev;

include/driver.h

@@ -292,6 +292,7 @@ struct file_operations {
 	off_t (*lseek)(struct cdev*, off_t);
 	int (*open)(struct cdev*);
 	int (*close)(struct cdev*);
+	int (*flush)(struct cdev*);
 	int (*erase)(struct cdev*, size_t count, unsigned long offset);
 	int (*protect)(struct cdev*, size_t count, unsigned long offset, int prot);
 	int (*memmap)(struct cdev*, void **map, int flags);

include/fs.h

@@ -53,6 +53,7 @@ struct fs_driver_d {
 	int (*close)(struct device_d *dev, FILE *f);
 	int (*read)(struct device_d *dev, FILE *f, void *buf, size_t size);
 	int (*write)(struct device_d *dev, FILE *f, const void *buf, size_t size);
+	int (*flush)(struct device_d *dev, FILE *f);
 	off_t (*lseek)(struct device_d *dev, FILE *f, off_t pos);
 
 	struct dir* (*opendir)(struct device_d *dev, const char *pathname);
@@ -98,6 +99,7 @@ int open(const char *pathname, int flags, ...);
 int creat(const char *pathname, mode_t mode);
 int unlink(const char *pathname);
 int close(int fd);
+int flush(int fd);
 int stat(const char *filename, struct stat *s);
 int read(int fd, void *buf, size_t count);
 int ioctl(int fd, int request, void *buf);