NFC: nfcmrvl: fix gpio-handling regression

Fix two reset-gpio sanity checks which were never converted to use
gpio_is_valid(), and make sure to use -EINVAL to indicate a missing
reset line also for the UART-driver module parameter and for the USB
driver.

This specifically prevents the UART and USB drivers from incidentally
trying to request and use gpio 0, and also avoids triggering a WARN() in
gpio_to_desc() during probe when no valid reset line has been specified.

Fixes: e33a3f8 ("NFC: nfcmrvl: allow gpio 0 for reset signalling")
Reported-by: syzbot+cf35b76f35e068a1107f@syzkaller.appspotmail.com
Tested-by: syzbot+cf35b76f35e068a1107f@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/nfc/nfcmrvl/main.c

@@ -244,7 +244,7 @@ void nfcmrvl_chip_reset(struct nfcmrvl_private *priv)
 	/* Reset possible fault of previous session */
 	clear_bit(NFCMRVL_PHY_ERROR, &priv->flags);
 
-	if (priv->config.reset_n_io) {
+	if (gpio_is_valid(priv->config.reset_n_io)) {
 		nfc_info(priv->dev, "reset the chip\n");
 		gpio_set_value(priv->config.reset_n_io, 0);
 		usleep_range(5000, 10000);
@@ -255,7 +255,7 @@ void nfcmrvl_chip_reset(struct nfcmrvl_private *priv)
 
 void nfcmrvl_chip_halt(struct nfcmrvl_private *priv)
 {
-	if (priv->config.reset_n_io)
+	if (gpio_is_valid(priv->config.reset_n_io))
 		gpio_set_value(priv->config.reset_n_io, 0);
 }
 

drivers/nfc/nfcmrvl/uart.c

@@ -26,7 +26,7 @@
 static unsigned int hci_muxed;
 static unsigned int flow_control;
 static unsigned int break_control;
-static unsigned int reset_n_io;
+static int reset_n_io = -EINVAL;
 
 /*
 ** NFCMRVL NCI OPS
@@ -231,5 +231,5 @@ MODULE_PARM_DESC(break_control, "Tell if UART driver must drive break signal.");
 module_param(hci_muxed, uint, 0);
 MODULE_PARM_DESC(hci_muxed, "Tell if transport is muxed in HCI one.");
 
-module_param(reset_n_io, uint, 0);
+module_param(reset_n_io, int, 0);
 MODULE_PARM_DESC(reset_n_io, "GPIO that is wired to RESET_N signal.");

drivers/nfc/nfcmrvl/usb.c

@@ -305,6 +305,7 @@ static int nfcmrvl_probe(struct usb_interface *intf,
 
 	/* No configuration for USB */
 	memset(&config, 0, sizeof(config));
+	config.reset_n_io = -EINVAL;
 
 	nfc_info(&udev->dev, "intf %p id %p\n", intf, id);