[PATCH v4 2/3] bus: mhi: ep: Add mhi_ep_queue_buf() API for raw buffer queuing

[Sumit Kumar]

Some MHI endpoint clients do not use socket buffers and need a way to queue
raw buffers for DL transfers. Add mhi_ep_queue_buf() to support this use
case.

Refactor mhi_ep_queue_skb() to delegate to a new internal mhi_ep_queue()
helper shared by both APIs, and rename mhi_ep_skb_completion() to
mhi_ep_buf_completion() to reflect its broader use.

Signed-off-by: Sumit Kumar <sumit.kumar@xxxxxxxxxxxxxxxx>
---
 drivers/bus/mhi/ep/main.c | 29 ++++++++++++++++++++---------
 include/linux/mhi_ep.h    | 15 +++++++++++++++
 2 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
index b3eafcf2a2c50d95e3efd3afb27038ecf55552a5..d44e1e54cfb4404b6589aab372e687db7492d3c3 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -516,7 +516,7 @@ static int mhi_ep_process_ch_ring(struct mhi_ep_ring *ring)
 	return 0;
 }
 
-static void mhi_ep_skb_completion(struct mhi_ep_buf_info *buf_info)
+static void mhi_ep_buf_completion(struct mhi_ep_buf_info *buf_info)
 {
 	struct mhi_ep_device *mhi_dev = buf_info->mhi_dev;
 	struct mhi_ep_cntrl *mhi_cntrl = mhi_dev->mhi_cntrl;
@@ -544,22 +544,22 @@ static void mhi_ep_skb_completion(struct mhi_ep_buf_info *buf_info)
 
 	mhi_ep_ring_inc_index(ring);
 }
-
 /* TODO: Handle partially formed TDs */
-int mhi_ep_queue_skb(struct mhi_ep_device *mhi_dev, struct sk_buff *skb)
+static int mhi_ep_queue(struct mhi_ep_device *mhi_dev, void *buf, size_t len,
+			void *cb_buf)
 {
 	struct mhi_ep_cntrl *mhi_cntrl = mhi_dev->mhi_cntrl;
 	struct mhi_ep_chan *mhi_chan = mhi_dev->dl_chan;
 	struct device *dev = &mhi_chan->mhi_dev->dev;
 	struct mhi_ep_buf_info buf_info = {};
 	struct mhi_ring_element *el;
-	u32 buf_left, read_offset;
+	size_t buf_left, read_offset;
 	struct mhi_ep_ring *ring;
 	size_t tr_len;
 	u32 tre_len;
 	int ret;
 
-	buf_left = skb->len;
+	buf_left = len;
 	ring = &mhi_cntrl->mhi_chan[mhi_chan->chan].ring;
 
 	mutex_lock(&mhi_chan->lock);
@@ -582,13 +582,13 @@ int mhi_ep_queue_skb(struct mhi_ep_device *mhi_dev, struct sk_buff *skb)
 		tre_len = MHI_TRE_DATA_GET_LEN(el);
 
 		tr_len = min(buf_left, tre_len);
-		read_offset = skb->len - buf_left;
+		read_offset = len - buf_left;
 
-		buf_info.dev_addr = skb->data + read_offset;
+		buf_info.dev_addr = buf + read_offset;
 		buf_info.host_addr = MHI_TRE_DATA_GET_PTR(el);
 		buf_info.size = tr_len;
-		buf_info.cb = mhi_ep_skb_completion;
-		buf_info.cb_buf = skb;
+		buf_info.cb = mhi_ep_buf_completion;
+		buf_info.cb_buf = cb_buf;
 		buf_info.mhi_dev = mhi_dev;
 
 		/*
@@ -627,8 +627,19 @@ int mhi_ep_queue_skb(struct mhi_ep_device *mhi_dev, struct sk_buff *skb)
 
 	return ret;
 }
+
+int mhi_ep_queue_skb(struct mhi_ep_device *mhi_dev, struct sk_buff *skb)
+{
+	return mhi_ep_queue(mhi_dev, skb->data, skb->len, skb);
+}
 EXPORT_SYMBOL_GPL(mhi_ep_queue_skb);
 
+int mhi_ep_queue_buf(struct mhi_ep_device *mhi_dev, void *buf, size_t len)
+{
+	return mhi_ep_queue(mhi_dev, buf, len, buf);
+}
+EXPORT_SYMBOL_GPL(mhi_ep_queue_buf);
+
 static int mhi_ep_cache_host_cfg(struct mhi_ep_cntrl *mhi_cntrl)
 {
 	size_t cmd_ctx_host_size, ch_ctx_host_size, ev_ctx_host_size;
diff --git a/include/linux/mhi_ep.h b/include/linux/mhi_ep.h
index 7b40fc8cbe77ab8419d167e89264b69a817b9fb1..59f796e56207aaf8be09edc9ba4d1f59b665581f 100644
--- a/include/linux/mhi_ep.h
+++ b/include/linux/mhi_ep.h
@@ -302,4 +302,19 @@ bool mhi_ep_queue_is_empty(struct mhi_ep_device *mhi_dev, enum dma_data_directio
  */
 int mhi_ep_queue_skb(struct mhi_ep_device *mhi_dev, struct sk_buff *skb);
 
+/**
+ * mhi_ep_queue_buf - Send buffer to host over MHI Endpoint
+ * @mhi_dev: Device associated with the DL channel
+ * @buf: Buffer to be queued. On success, ownership passes to the MHI stack;
+ *       the caller must not free @buf until the DL transfer callback fires
+ *       with result->buf_addr equal to @buf. On failure, the caller retains
+ *       ownership and must free @buf.
+ *       Note: if @len spans multiple host DL TREs, the DL transfer callback
+ *       fires once per TRE, each time with result->buf_addr equal to @buf.
+ * @len: Size of the buffer
+ *
+ * Return: 0 if the buffer has been sent successfully, a negative error code otherwise.
+ */
+int mhi_ep_queue_buf(struct mhi_ep_device *mhi_dev, void *buf, size_t len);
+
 #endif

-- 
2.34.1