linux-kernel - [PATCH v2 3/3] firewire: add kernel API to access packet structure in request structure for AR context

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Message-Id: <20220212022131.199855-4-o-takashi@sakamocchi.jp>
Date:   Sat, 12 Feb 2022 11:21:31 +0900
From:   Takashi Sakamoto <o-takashi@...amocchi.jp>
To:     stefanr@...6.in-berlin.de
Cc:     linux1394-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, clemens@...isch.de,
        alsa-devel@...a-project.org
Subject: [PATCH v2 3/3] firewire: add kernel API to access packet structure in request structure for AR context

In 1394 OHCI specification, descriptor of Asynchronous Receive DMA context
has timeStamp field in its trailer quadlet. The field is written by
the host controller for the time to receive asynchronous request
subaction in isochronous cycle time.

In Linux FireWire subsystem, the value of field is stored to fw_packet
structure and copied to fw_request structure as the part. The fw_request
structure is hidden from unit driver and passed as opaque pointer when
calling registered handler. It's inconvenient to the unit driver which
needs timestamp of packet.

This commit adds kernel API to pick up timestamp from opaque pointer to
fw_request structure.
---
 drivers/firewire/core-transaction.c | 18 ++++++++++++++++++
 include/linux/firewire.h            |  1 +
 2 files changed, 19 insertions(+)

diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-transaction.c
index ac487c96bb71..e12a0a4c33f7 100644
--- a/drivers/firewire/core-transaction.c
+++ b/drivers/firewire/core-transaction.c
@@ -619,6 +619,7 @@ struct fw_request {
 	struct fw_packet response;
 	u32 request_header[4];
 	int ack;
+	u32 timestamp;
 	u32 length;
 	u32 data[];
 };
@@ -788,6 +789,7 @@ static struct fw_request *allocate_request(struct fw_card *card,
 	request->response.ack = 0;
 	request->response.callback = free_response_callback;
 	request->ack = p->ack;
+	request->timestamp = p->timestamp;
 	request->length = length;
 	if (data)
 		memcpy(request->data, data, length);
@@ -832,6 +834,22 @@ int fw_get_request_speed(struct fw_request *request)
 }
 EXPORT_SYMBOL(fw_get_request_speed);
 
+/**
+ * fw_request_get_timestamp: Get timestamp of the request.
+ * @request: The opaque pointer to request structure.
+ *
+ * Get timestamp when 1394 OHCI controller receives the asynchronous request subaction. The
+ * timestamp consists of the low order 3 bits of second field and the full 13 bits of count
+ * field of isochronous cycle time register.
+ *
+ * Returns: timestamp of the request.
+ */
+u32 fw_request_get_timestamp(const struct fw_request *request)
+{
+	return request->timestamp;
+}
+EXPORT_SYMBOL_GPL(fw_request_get_timestamp);
+
 static void handle_exclusive_region_request(struct fw_card *card,
 					    struct fw_packet *p,
 					    struct fw_request *request,
diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index 2f467c52bdec..980019053e54 100644
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -354,6 +354,7 @@ void fw_core_remove_address_handler(struct fw_address_handler *handler);
 void fw_send_response(struct fw_card *card,
 		      struct fw_request *request, int rcode);
 int fw_get_request_speed(struct fw_request *request);
+u32 fw_request_get_timestamp(const struct fw_request *request);
 void fw_send_request(struct fw_card *card, struct fw_transaction *t,
 		     int tcode, int destination_id, int generation, int speed,
 		     unsigned long long offset, void *payload, size_t length,
-- 
2.32.0