[PATCH v2] staging: gdm72xx: fix address space warnings

[Okash Khawaja <okash.khawaja@gmail.com>]

copy_to_user() and copy_from_user() functions expect the user space
pointers to be marked with __user. Sparse throws following warnings.

For copy_to_user():

warning: incorrect type in argument 1 (different address spaces)
expected void [noderef] <asn:1>*to
got void *buf

For copy_from_user():

warning: incorrect type in argument 2 (different address spaces)
expected void const [noderef] <asn:1>*from
got void *buf

This creates a separate `struct udata_s` which is user space counterpart
of `struct data_s`. This patch also alters function signatures where
data transfer between user and kernel space occurs, in order to make the
distinction explicit. Finally, it explicitly casts the argument passed
to `gdm_update_fsm()` using __force to avoid the warning "cast removes
address space of expression".

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
---
 drivers/staging/gdm72xx/gdm_wimax.c | 7 ++++---
 drivers/staging/gdm72xx/wm_ioctl.h  | 7 ++++++-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/gdm72xx/gdm_wimax.c b/drivers/staging/gdm72xx/gdm_wimax.c
index b8eea21..c61ce92 100644
--- a/drivers/staging/gdm72xx/gdm_wimax.c
+++ b/drivers/staging/gdm72xx/gdm_wimax.c
@@ -363,7 +363,7 @@ static void kdelete(void **buf)
 	}
 }
 
-static int gdm_wimax_ioctl_get_data(struct data_s *dst, struct data_s *src)
+static int gdm_wimax_ioctl_get_data(struct udata_s *dst, struct data_s *src)
 {
 	int size;
 
@@ -379,7 +379,7 @@ static int gdm_wimax_ioctl_get_data(struct data_s *dst, struct data_s *src)
 	return 0;
 }
 
-static int gdm_wimax_ioctl_set_data(struct data_s *dst, struct data_s *src)
+static int gdm_wimax_ioctl_set_data(struct data_s *dst, struct udata_s *src)
 {
 	if (!src->size) {
 		dst->size = 0;
@@ -478,7 +478,8 @@ static int gdm_wimax_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 				 * before gdm_wimax_ioctl_set_data is called.
 				 */
 				gdm_update_fsm(dev,
-					       req->data.buf);
+						(__force struct fsm_s *)
+						req->data.buf);
 			}
 			ret = gdm_wimax_ioctl_set_data(
 				&nic->sdk_data[req->data_id], &req->data);
diff --git a/drivers/staging/gdm72xx/wm_ioctl.h b/drivers/staging/gdm72xx/wm_ioctl.h
index ed8f649..7dc8f6f 100644
--- a/drivers/staging/gdm72xx/wm_ioctl.h
+++ b/drivers/staging/gdm72xx/wm_ioctl.h
@@ -78,13 +78,18 @@ struct data_s {
 	void	*buf;
 };
 
+struct udata_s {
+	unsigned int size;
+	void __user *buf;
+};
+
 struct wm_req_s {
 	union {
 		char ifrn_name[IFNAMSIZ];
 	} ifr_ifrn;
 	unsigned short	cmd;
 	unsigned short	data_id;
-	struct data_s	data;
+	struct udata_s	data;
 
 /* NOTE: sizeof(struct wm_req_s) must be less than sizeof(struct ifreq). */
 };
-- 
2.5.2