[media] cec: add proper support for CDC-Only CEC devices

CDC-Only CEC devices are CEC devices that can only handle CDC messages,
all other messages are ignored.

Add a flag to signal that this is a CDC-Only device and act accordingly.

Also add helper functions to identify if a CEC device is configured as a
CDC-Only device, a second TV, a switch or a processor, since these variations
cannot be determined by the logical address alone.

Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/staging/media/cec/TODO

···
 TODOs:
 
-- Should CEC_LOG_ADDR_TYPE_SPECIFIC be replaced by TYPE_2ND_TV and TYPE_PROCESSOR?
-  And also TYPE_SWITCH and TYPE_CDC_ONLY in addition to the TYPE_UNREGISTERED?
-  This should give the framework more information about the device type
-  since SPECIFIC and UNREGISTERED give no useful information.
 - Once this is out of staging this should no longer be a separate
   config option, instead it should be selected by drivers that want it.
 - Revisit the IS_REACHABLE(RC_CORE): perhaps the RC_CORE support should

drivers/staging/media/cec/cec-adap.c

···
 	mutex_unlock(&adap->lock);
 
 	for (i = 0; i < las->num_log_addrs; i++) {
-		if (las->log_addr[i] == CEC_LOG_ADDR_INVALID)
+		if (las->log_addr[i] == CEC_LOG_ADDR_INVALID ||
+		    (las->flags & CEC_LOG_ADDRS_FL_CDC_ONLY))
 			continue;
 
 		/*
···
 		adap->log_addrs.num_log_addrs = 0;
 		cec_adap_unconfigure(adap);
 		return 0;
+	}
+
+	if (log_addrs->flags & CEC_LOG_ADDRS_FL_CDC_ONLY) {
+		/*
+		 * Sanitize log_addrs fields if a CDC-Only device is
+		 * requested.
+		 */
+		log_addrs->num_log_addrs = 1;
+		log_addrs->osd_name[0] = '\0';
+		log_addrs->vendor_id = CEC_VENDOR_ID_NONE;
+		log_addrs->log_addr_type[0] = CEC_LOG_ADDR_TYPE_UNREGISTERED;
+		/*
+		 * This is just an internal convention since a CDC-Only device
+		 * doesn't have to be a switch. But switches already use
+		 * unregistered, so it makes some kind of sense to pick this
+		 * as the primary device. Since a CDC-Only device never sends
+		 * any 'normal' CEC messages this primary device type is never
+		 * sent over the CEC bus.
+		 */
+		log_addrs->primary_device_type[0] = CEC_OP_PRIM_DEVTYPE_SWITCH;
+		log_addrs->all_device_types[0] = 0;
+		log_addrs->features[0][0] = 0;
+		log_addrs->features[0][1] = 0;
 	}
 
 	/* Ensure the osd name is 0-terminated */
···
 	struct cec_msg tx_cec_msg = { };
 
 	dprintk(1, "cec_receive_notify: %*ph\n", msg->len, msg->msg);
+
+	/* If this is a CDC-Only device, then ignore any non-CDC messages */
+	if (cec_is_cdc_only(&adap->log_addrs) &&
+	    msg->msg[1] != CEC_MSG_CDC_MESSAGE)
+		return 0;
 
 	if (adap->ops->received) {
 		/* Allow drivers to process the message first */

drivers/staging/media/cec/cec-api.c

···
 	if (copy_from_user(&log_addrs, parg, sizeof(log_addrs)))
 		return -EFAULT;
 	log_addrs.flags &= CEC_LOG_ADDRS_FL_ALLOW_UNREG_FALLBACK |
-			   CEC_LOG_ADDRS_FL_ALLOW_RC_PASSTHRU;
+			   CEC_LOG_ADDRS_FL_ALLOW_RC_PASSTHRU |
+			   CEC_LOG_ADDRS_FL_CDC_ONLY;
 	mutex_lock(&adap->lock);
 	if (!adap->is_configuring &&
 	    (!log_addrs.num_log_addrs || !adap->is_configured) &&
···
 		return -ENOTTY;
 	if (copy_from_user(&msg, parg, sizeof(msg)))
 		return -EFAULT;
+
+	/* A CDC-Only device can only send CDC messages */
+	if ((adap->log_addrs.flags & CEC_LOG_ADDRS_FL_CDC_ONLY) &&
+	    (msg.len == 1 || msg.msg[1] != CEC_MSG_CDC_MESSAGE))
+		return -EINVAL;
+
 	msg.flags &= CEC_MSG_FL_REPLY_TO_FOLLOWERS;
 	mutex_lock(&adap->lock);
 	if (!adap->is_configured)

include/linux/cec.h

···
 #define CEC_LOG_ADDRS_FL_ALLOW_UNREG_FALLBACK	(1 << 0)
 /* Passthrough RC messages to the input subsystem */
 #define CEC_LOG_ADDRS_FL_ALLOW_RC_PASSTHRU	(1 << 1)
+/* CDC-Only device: supports only CDC messages */
+#define CEC_LOG_ADDRS_FL_CDC_ONLY		(1 << 2)
 
 /* Events */
 
···
 #define CEC_OP_HPD_ERROR_INITIATOR_WRONG_STATE		2
 #define CEC_OP_HPD_ERROR_OTHER				3
 #define CEC_OP_HPD_ERROR_NONE_NO_VIDEO			4
+
+/* End of Messages */
+
+/* Helper functions to identify the 'special' CEC devices */
+
+static inline bool cec_is_2nd_tv(const struct cec_log_addrs *las)
+{
+	/*
+	 * It is a second TV if the logical address is 14 or 15 and the
+	 * primary device type is a TV.
+	 */
+	return las->num_log_addrs &&
+	       las->log_addr[0] >= CEC_LOG_ADDR_SPECIFIC &&
+	       las->primary_device_type[0] == CEC_OP_PRIM_DEVTYPE_TV;
+}
+
+static inline bool cec_is_processor(const struct cec_log_addrs *las)
+{
+	/*
+	 * It is a processor if the logical address is 12-15 and the
+	 * primary device type is a Processor.
+	 */
+	return las->num_log_addrs &&
+	       las->log_addr[0] >= CEC_LOG_ADDR_BACKUP_1 &&
+	       las->primary_device_type[0] == CEC_OP_PRIM_DEVTYPE_PROCESSOR;
+}
+
+static inline bool cec_is_switch(const struct cec_log_addrs *las)
+{
+	/*
+	 * It is a switch if the logical address is 15 and the
+	 * primary device type is a Switch and the CDC-Only flag is not set.
+	 */
+	return las->num_log_addrs == 1 &&
+	       las->log_addr[0] == CEC_LOG_ADDR_UNREGISTERED &&
+	       las->primary_device_type[0] == CEC_OP_PRIM_DEVTYPE_SWITCH &&
+	       !(las->flags & CEC_LOG_ADDRS_FL_CDC_ONLY);
+}
+
+static inline bool cec_is_cdc_only(const struct cec_log_addrs *las)
+{
+	/*
+	 * It is a CDC-only device if the logical address is 15 and the
+	 * primary device type is a Switch and the CDC-Only flag is set.
+	 */
+	return las->num_log_addrs == 1 &&
+	       las->log_addr[0] == CEC_LOG_ADDR_UNREGISTERED &&
+	       las->primary_device_type[0] == CEC_OP_PRIM_DEVTYPE_SWITCH &&
+	       (las->flags & CEC_LOG_ADDRS_FL_CDC_ONLY);
+}
 
 #endif