staging: comedi: return error on "write" if no command set up

[deliverable/linux.git] / drivers / staging / comedi / comedi_fops.c

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 188a12a02ce731caf0de8e575f589a13e2b0817d..2a2b5a06ed0e97bfc8d0cef935f3db7f5ca7eb16 100644 (file)
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -2331,9 +2331,12 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
        }
 
        async = s->async;
-
-       if (!s->busy || !nbytes)
+       if (!nbytes)
+               goto out;
+       if (!s->busy) {
+               retval = -EINVAL;
                goto out;
+       }
        if (s->busy != file) {
                retval = -EACCES;
                goto out;
@@ -2346,6 +2349,7 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
        add_wait_queue(&async->wait_head, &wait);
        while (count == 0 && !retval) {
                unsigned runflags;
+               unsigned int wp, n1, n2;
 
                set_current_state(TASK_INTERRUPTIBLE);
 
@@ -2357,16 +2361,10 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
                        break;
                }
 
-               n = nbytes;
-
-               m = n;
-               if (async->buf_write_ptr + m > async->prealloc_bufsz)
-                       m = async->prealloc_bufsz - async->buf_write_ptr;
+               /* Allocate all free buffer space. */
                comedi_buf_write_alloc(s, async->prealloc_bufsz);
-               if (m > comedi_buf_write_n_allocated(s))
-                       m = comedi_buf_write_n_allocated(s);
-               if (m < n)
-                       n = m;
+               m = comedi_buf_write_n_allocated(s);
+               n = min_t(size_t, m, nbytes);
 
                if (n == 0) {
                        if (file->f_flags & O_NONBLOCK) {
@@ -2378,8 +2376,10 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
                                retval = -ERESTARTSYS;
                                break;
                        }
-                       if (!s->busy)
+                       if (!s->busy) {
+                               retval = -EINVAL;
                                break;
+                       }
                        if (s->busy != file) {
                                retval = -EACCES;
                                break;
@@ -2391,8 +2391,14 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
                        continue;
                }
 
-               m = copy_from_user(async->prealloc_buf + async->buf_write_ptr,
-                                  buf, n);
+               wp = async->buf_write_ptr;
+               n1 = min(n, async->prealloc_bufsz - wp);
+               n2 = n - n1;
+               m = copy_from_user(async->prealloc_buf + wp, buf, n1);
+               if (m)
+                       m += n2;
+               else if (n2)
+                       m = copy_from_user(async->prealloc_buf, buf + n1, n2);
                if (m) {
                        n -= m;
                        retval = -EFAULT;