nfc: hci: pass callback data param as pointer in nci_request()

The nci_request() receives a callback function and unsigned long data
argument "opt" which is passed to the callback.  Almost all of the
nci_request() callers pass pointer to a stack variable as data argument.
Only few pass scalar value (e.g. u8).

All such callbacks do not modify passed data argument and in previous
commit they were made as const.  However passing pointers via unsigned
long removes the const annotation.  The callback could simply cast
unsigned long to a pointer to writeable memory.

Use "const void *" as type of this "opt" argument to solve this and
prevent modifying the pointed contents.  This is also consistent with
generic pattern of passing data arguments - via "void *".  In few places
which pass scalar values, use casts via "unsigned long" to suppress any
warnings.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/nfc/nci_core.h

@@ -276,8 +276,8 @@ int nci_register_device(struct nci_dev *ndev);
 void nci_unregister_device(struct nci_dev *ndev);
 int nci_request(struct nci_dev *ndev,
 		void (*req)(struct nci_dev *ndev,
-			    unsigned long opt),
-		unsigned long opt, __u32 timeout);
+			    const void *opt),
+		const void *opt, __u32 timeout);
 int nci_prop_cmd(struct nci_dev *ndev, __u8 oid, size_t len,
 		 const __u8 *payload);
 int nci_core_cmd(struct nci_dev *ndev, __u16 opcode, size_t len,

net/nfc/nci/hci.c

@@ -195,9 +195,9 @@ static int nci_hci_send_data(struct nci_dev *ndev, u8 pipe,
 	return i;
 }
 
-static void nci_hci_send_data_req(struct nci_dev *ndev, unsigned long opt)
+static void nci_hci_send_data_req(struct nci_dev *ndev, const void *opt)
 {
-	const struct nci_data *data = (struct nci_data *)opt;
+	const struct nci_data *data = opt;
 
 	nci_hci_send_data(ndev, data->pipe, data->cmd,
 			  data->data, data->data_len);
@@ -240,7 +240,7 @@ int nci_hci_send_cmd(struct nci_dev *ndev, u8 gate, u8 cmd,
 	data.data = param;
 	data.data_len = param_len;
 
-	r = nci_request(ndev, nci_hci_send_data_req, (unsigned long)&data,
+	r = nci_request(ndev, nci_hci_send_data_req, &data,
 			msecs_to_jiffies(NCI_DATA_TIMEOUT));
 	if (r == NCI_STATUS_OK) {
 		message = (struct nci_hcp_message *)conn_info->rx_skb->data;
@@ -511,8 +511,7 @@ int nci_hci_open_pipe(struct nci_dev *ndev, u8 pipe)
 	data.data = NULL;
 	data.data_len = 0;
 
-	return nci_request(ndev, nci_hci_send_data_req,
-			(unsigned long)&data,
+	return nci_request(ndev, nci_hci_send_data_req, &data,
 			   msecs_to_jiffies(NCI_DATA_TIMEOUT));
 }
 EXPORT_SYMBOL(nci_hci_open_pipe);
@@ -587,8 +586,7 @@ int nci_hci_set_param(struct nci_dev *ndev, u8 gate, u8 idx,
 	data.data = tmp;
 	data.data_len = param_len + 1;
 
-	r = nci_request(ndev, nci_hci_send_data_req,
-			(unsigned long)&data,
+	r = nci_request(ndev, nci_hci_send_data_req, &data,
 			msecs_to_jiffies(NCI_DATA_TIMEOUT));
 	if (r == NCI_STATUS_OK) {
 		message = (struct nci_hcp_message *)conn_info->rx_skb->data;
@@ -627,7 +625,7 @@ int nci_hci_get_param(struct nci_dev *ndev, u8 gate, u8 idx,
 	data.data = &idx;
 	data.data_len = 1;
 
-	r = nci_request(ndev, nci_hci_send_data_req, (unsigned long)&data,
+	r = nci_request(ndev, nci_hci_send_data_req, &data,
 			msecs_to_jiffies(NCI_DATA_TIMEOUT));
 
 	if (r == NCI_STATUS_OK) {