nfc: constify nci_ops

The struct nci_ops is modified by NFC core in only one case:
nci_allocate_device() receives too many proprietary commands (prop_ops)
to configure.  This is a build time known constrain, so a graceful
handling of such case is not necessary.

Instead, fail the nci_allocate_device() and add BUILD_BUG_ON() to places
which set these.

This allows to constify the struct nci_ops (consisting of function
pointers) for correctness and safety.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/nfc/fdp/fdp.c

@@ -675,7 +675,7 @@ static struct nci_driver_ops fdp_prop_ops[] = {
 	},
 };
 
-static struct nci_ops nci_ops = {
+static const struct nci_ops nci_ops = {
 	.open = fdp_nci_open,
 	.close = fdp_nci_close,
 	.send = fdp_nci_send,
@@ -718,6 +718,7 @@ int fdp_nci_probe(struct fdp_i2c_phy *phy, struct nfc_phy_ops *phy_ops,
 		    NFC_PROTO_NFC_DEP_MASK |
 		    NFC_PROTO_ISO15693_MASK;
 
+	BUILD_BUG_ON(ARRAY_SIZE(fdp_prop_ops) > NCI_MAX_PROPRIETARY_CMD);
 	ndev = nci_allocate_device(&nci_ops, protocols, tx_headroom,
 				   tx_tailroom);
 	if (!ndev) {

drivers/nfc/nfcmrvl/main.c

@@ -81,7 +81,7 @@ static int nfcmrvl_nci_fw_download(struct nci_dev *ndev,
 	return nfcmrvl_fw_dnld_start(ndev, firmware_name);
 }
 
-static struct nci_ops nfcmrvl_nci_ops = {
+static const struct nci_ops nfcmrvl_nci_ops = {
 	.open = nfcmrvl_nci_open,
 	.close = nfcmrvl_nci_close,
 	.send = nfcmrvl_nci_send,

drivers/nfc/nxp-nci/core.c

@@ -83,7 +83,7 @@ static int nxp_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
 	return r;
 }
 
-static struct nci_ops nxp_nci_ops = {
+static const struct nci_ops nxp_nci_ops = {
 	.open = nxp_nci_open,
 	.close = nxp_nci_close,
 	.send = nxp_nci_send,

drivers/nfc/st-nci/core.c

@@ -94,7 +94,7 @@ static struct nci_driver_ops st_nci_prop_ops[] = {
 	},
 };
 
-static struct nci_ops st_nci_ops = {
+static const struct nci_ops st_nci_ops = {
 	.init = st_nci_init,
 	.open = st_nci_open,
 	.close = st_nci_close,
@@ -131,6 +131,7 @@ int st_nci_probe(struct llt_ndlc *ndlc, int phy_headroom,
 		| NFC_PROTO_ISO15693_MASK
 		| NFC_PROTO_NFC_DEP_MASK;
 
+	BUILD_BUG_ON(ARRAY_SIZE(st_nci_prop_ops) > NCI_MAX_PROPRIETARY_CMD);
 	ndlc->ndev = nci_allocate_device(&st_nci_ops, protocols,
 					phy_headroom, phy_tailroom);
 	if (!ndlc->ndev) {

drivers/nfc/virtual_ncidev.c

@@ -65,7 +65,7 @@ static int virtual_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
 	return 0;
 }
 
-static struct nci_ops virtual_nci_ops = {
+static const struct nci_ops virtual_nci_ops = {
 	.open = virtual_nci_open,
 	.close = virtual_nci_close,
 	.send = virtual_nci_send

include/net/nfc/nci_core.h

@@ -194,7 +194,7 @@ struct nci_hci_dev {
 /* NCI Core structures */
 struct nci_dev {
 	struct nfc_dev		*nfc_dev;
-	struct nci_ops		*ops;
+	const struct nci_ops	*ops;
 	struct nci_hci_dev	*hci_dev;
 
 	int			tx_headroom;
@@ -267,7 +267,7 @@ struct nci_dev {
 };
 
 /* ----- NCI Devices ----- */
-struct nci_dev *nci_allocate_device(struct nci_ops *ops,
+struct nci_dev *nci_allocate_device(const struct nci_ops *ops,
 				    __u32 supported_protocols,
 				    int tx_headroom,
 				    int tx_tailroom);

net/nfc/nci/core.c

@@ -1129,7 +1129,7 @@ static struct nfc_ops nci_nfc_ops = {
  * @tx_headroom: Reserved space at beginning of skb
  * @tx_tailroom: Reserved space at end of skb
  */
-struct nci_dev *nci_allocate_device(struct nci_ops *ops,
+struct nci_dev *nci_allocate_device(const struct nci_ops *ops,
 				    __u32 supported_protocols,
 				    int tx_headroom, int tx_tailroom)
 {
@@ -1152,8 +1152,7 @@ struct nci_dev *nci_allocate_device(struct nci_ops *ops,
 	if (ops->n_prop_ops > NCI_MAX_PROPRIETARY_CMD) {
 		pr_err("Too many proprietary commands: %zd\n",
 		       ops->n_prop_ops);
-		ops->prop_ops = NULL;
-		ops->n_prop_ops = 0;
+		goto free_nci;
 	}
 
 	ndev->tx_headroom = tx_headroom;