V4L/DVB: ir-core: Add support for disabling all protocols

Writing "none" to /dev/class/rc/rc*/protocols will disable all protocols.
This allows an easier setup, from userspace, as userspace applications don't
need to disable protocol per protocol, before enabling a different set of
protocols.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/IR/ir-sysfs.c

@@ -45,6 +45,8 @@ static struct {
 	{ IR_TYPE_SONY,		"sony"		},
 };
 
+#define PROTO_NONE	"none"
+
 /**
  * show_protocols() - shows the current IR protocol(s)
  * @d:		the device descriptor
@@ -101,6 +103,7 @@ static ssize_t show_protocols(struct device *d,
  * Writing "+proto" will add a protocol to the list of enabled protocols.
  * Writing "-proto" will remove a protocol from the list of enabled protocols.
  * Writing "proto" will enable only "proto".
+ * Writing "none" will disable all protocols.
  * Returns -EINVAL if an invalid protocol combination or unknown protocol name
  * is used, otherwise @len.
  */
@@ -134,6 +137,11 @@ static ssize_t store_protocols(struct device *d,
 		disable = false;
 	}
 
+
+	if (!enable && !disable && !strncasecmp(tmp, PROTO_NONE, sizeof(PROTO_NONE))) {
+		mask = 0;
+		tmp += sizeof(PROTO_NONE);
+	} else {
 		for (i = 0; i < ARRAY_SIZE(proto_names); i++) {
 			if (!strncasecmp(tmp, proto_names[i].name, strlen(proto_names[i].name))) {
 				tmp += strlen(proto_names[i].name);
@@ -145,6 +153,7 @@ static ssize_t store_protocols(struct device *d,
 			IR_dprintk(1, "Unknown protocol\n");
 			return -EINVAL;
 		}
+	}
 
 	tmp = skip_spaces(tmp);
 	if (*tmp != '\0') {