2 files changed, 20 insertions, 1 deletions

diff --git a/include/litmus/ftdev.h b/include/litmus/ftdev.h
index 348387e9adf9..0b959874dd70 100644
--- a/include/litmus/ftdev.h
+++ b/include/litmus/ftdev.h
@@ -16,7 +16,8 @@ typedef int  (*ftdev_can_open_t)(struct ftdev* dev, unsigned int buf_no);
 /* return 0 on success, otherwise -$REASON */
 typedef int  (*ftdev_alloc_t)(struct ftdev* dev, unsigned int buf_no);
 typedef void (*ftdev_free_t)(struct ftdev* dev, unsigned int buf_no);
-
+/* Let devices handle writes from userspace. No synchronization provided. */
+typedef ssize_t (*ftdev_write_t)(struct ft_buffer* buf, size_t len, const char __user *from);
 
 struct ftdev_event;
 
@@ -27,6 +28,7 @@ struct ftdev_minor {
         /* FIXME: filter for authorized events */
         struct ftdev_event*     events;
         struct device*          device;
+        struct ftdev*           ftdev;
 };
 
 struct ftdev {
@@ -39,6 +41,7 @@ struct ftdev {
         ftdev_alloc_t           alloc;
         ftdev_free_t            free;
         ftdev_can_open_t        can_open;
+        ftdev_write_t           write;
 };
 
 struct ft_buffer* alloc_ft_buffer(unsigned int count, size_t size);
diff --git a/litmus/ftdev.c b/litmus/ftdev.c
index 216dc0b4cb94..06fcf4cf77dc 100644
--- a/litmus/ftdev.c
+++ b/litmus/ftdev.c
@@ -114,6 +114,7 @@ static int ftdev_open(struct inode *in, struct file *filp)
                 goto out;
 
         ftdm = ftdev->minor + buf_idx;
+        ftdm->ftdev = ftdev;
         filp->private_data = ftdm;
 
         if (mutex_lock_interruptible(&ftdm->lock)) {
@@ -284,11 +285,25 @@ out:
         return err;
 }
 
+static ssize_t ftdev_write(struct file *filp, const char __user *from,
+                           size_t len, loff_t *f_pos)
+{
+        struct ftdev_minor* ftdm = filp->private_data;
+        ssize_t err = -EINVAL;
+        struct ftdev* ftdev = ftdm->ftdev;
+
+        /* dispatch write to buffer-specific code, if available */
+        if (ftdev->write)
+                err = ftdev->write(ftdm->buf, len, from);
+
+        return err;
+}
 
 struct file_operations ftdev_fops = {
         .owner   = THIS_MODULE,
         .open    = ftdev_open,
         .release = ftdev_release,
+        .write   = ftdev_write,
         .read    = ftdev_read,
         .unlocked_ioctl = ftdev_ioctl,
 };
@@ -308,6 +323,7 @@ int ftdev_init(	struct ftdev* ftdev, struct module* owner,
         ftdev->alloc    = NULL;
         ftdev->free     = NULL;
         ftdev->can_open = NULL;
+        ftdev->write    = NULL;
 
         ftdev->minor = kcalloc(ftdev->minor_cnt, sizeof(*ftdev->minor),
                         GFP_KERNEL);