platform/surface: aggregator: Improve documentation and handling of message target and source IDs

The `tid_in` and `tid_out` fields of the serial hub protocol command
struct (struct ssh_command) are actually source and target IDs,
indicating the peer from which the message originated and the peer for
which it is intended.

Change the naming of those fields accordingly and improve the protocol
documentation. Additionally, introduce an enum containing all currently
known peers, i.e. targets and sources.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Link: https://lore.kernel.org/r/20221202223327.690880-3-luzmaximilian@gmail.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

3 files changed, 14 insertions, 13 deletions

diff --git a/drivers/platform/surface/aggregator/controller.c b/drivers/platform/surface/aggregator/controller.c
index c6537a1b3a2e..2c99f51ccd4e 100644
--- a/drivers/platform/surface/aggregator/controller.c
+++ b/drivers/platform/surface/aggregator/controller.c
@@ -994,7 +994,7 @@ static void ssam_handle_event(struct ssh_rtl *rtl,
 
 	item->rqid = get_unaligned_le16(&cmd->rqid);
 	item->event.target_category = cmd->tc;
-	item->event.target_id = cmd->tid_in;
+	item->event.target_id = cmd->sid;
 	item->event.command_id = cmd->cid;
 	item->event.instance_id = cmd->iid;
 	memcpy(&item->event.data[0], data->ptr, data->len);
@@ -1779,35 +1779,35 @@ EXPORT_SYMBOL_GPL(ssam_request_sync_with_buffer);
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_get_firmware_version, __le32, {
 	.target_category = SSAM_SSH_TC_SAM,
-	.target_id       = 0x01,
+	.target_id       = SSAM_SSH_TID_SAM,
 	.command_id      = 0x13,
 	.instance_id     = 0x00,
 });
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_display_off, u8, {
 	.target_category = SSAM_SSH_TC_SAM,
-	.target_id       = 0x01,
+	.target_id       = SSAM_SSH_TID_SAM,
 	.command_id      = 0x15,
 	.instance_id     = 0x00,
 });
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_display_on, u8, {
 	.target_category = SSAM_SSH_TC_SAM,
-	.target_id       = 0x01,
+	.target_id       = SSAM_SSH_TID_SAM,
 	.command_id      = 0x16,
 	.instance_id     = 0x00,
 });
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_d0_exit, u8, {
 	.target_category = SSAM_SSH_TC_SAM,
-	.target_id       = 0x01,
+	.target_id       = SSAM_SSH_TID_SAM,
 	.command_id      = 0x33,
 	.instance_id     = 0x00,
 });
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_d0_entry, u8, {
 	.target_category = SSAM_SSH_TC_SAM,
-	.target_id       = 0x01,
+	.target_id       = SSAM_SSH_TID_SAM,
 	.command_id      = 0x34,
 	.instance_id     = 0x00,
 });
diff --git a/drivers/platform/surface/aggregator/ssh_msgb.h b/drivers/platform/surface/aggregator/ssh_msgb.h
index f3ecad92eefd..438873e06098 100644
--- a/drivers/platform/surface/aggregator/ssh_msgb.h
+++ b/drivers/platform/surface/aggregator/ssh_msgb.h
@@ -189,8 +189,8 @@ static inline void msgb_push_cmd(struct msgbuf *msgb, u8 seq, u16 rqid,
 
 	__msgb_push_u8(msgb, SSH_PLD_TYPE_CMD);		/* Payload type. */
 	__msgb_push_u8(msgb, rqst->target_category);	/* Target category. */
-	__msgb_push_u8(msgb, rqst->target_id);		/* Target ID (out). */
-	__msgb_push_u8(msgb, 0x00);			/* Target ID (in). */
+	__msgb_push_u8(msgb, rqst->target_id);		/* Target ID. */
+	__msgb_push_u8(msgb, SSAM_SSH_TID_HOST);	/* Source ID. */
 	__msgb_push_u8(msgb, rqst->instance_id);	/* Instance ID. */
 	__msgb_push_u16(msgb, rqid);			/* Request ID. */
 	__msgb_push_u8(msgb, rqst->command_id);		/* Command ID. */
diff --git a/drivers/platform/surface/aggregator/ssh_request_layer.c b/drivers/platform/surface/aggregator/ssh_request_layer.c
index 69132976d297..90634dcacabf 100644
--- a/drivers/platform/surface/aggregator/ssh_request_layer.c
+++ b/drivers/platform/surface/aggregator/ssh_request_layer.c
@@ -920,13 +920,14 @@ static void ssh_rtl_rx_command(struct ssh_ptl *p, const struct ssam_span *data)
 	 * Check if the message was intended for us. If not, drop it.
 	 *
 	 * Note: We will need to change this to handle debug messages. On newer
-	 * generation devices, these seem to be sent to tid_out=0x03. We as
-	 * host can still receive them as they can be forwarded via an override
-	 * option on SAM, but doing so does not change tid_out=0x00.
+	 * generation devices, these seem to be sent to SSAM_SSH_TID_DEBUG. We
+	 * as host can still receive them as they can be forwarded via an
+	 * override option on SAM, but doing so does not change the target ID
+	 * to SSAM_SSH_TID_HOST.
 	 */
-	if (command->tid_out != 0x00) {
+	if (command->tid != SSAM_SSH_TID_HOST) {
 		rtl_warn(rtl, "rtl: dropping message not intended for us (tid = %#04x)\n",
-			 command->tid_out);
+			 command->tid);
 		return;
 	}