The "cbd_channel" is the component responsible for the interaction
between the blkdev and the backend. It mainly provides the functions
"cbdc_copy_to_bio", "cbdc_copy_from_bio" and "cbd_channel_crc"

If the blkdev or backend is alive, that means there is active
user for this channel, then channel is alive.

Signed-off-by: Dongsheng Yang <dongsheng.yang@linux.dev>
---
 drivers/block/cbd/cbd_channel.c | 96 +++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 drivers/block/cbd/cbd_channel.c

diff --git a/drivers/block/cbd/cbd_channel.c b/drivers/block/cbd/cbd_channel.c
new file mode 100644
index 000000000000..6d3f77b9dc79
--- /dev/null
+++ b/drivers/block/cbd/cbd_channel.c
@@ -0,0 +1,96 @@
+#include "cbd_internal.h"
+
+static void channel_format(struct cbd_transport *cbdt, u32 id)
+{
+	struct cbd_channel_info *channel_info = cbdt_get_channel_info(cbdt, id);
+
+	cbdt_zero_range(cbdt, channel_info, CBDC_META_SIZE);
+}
+
+int cbd_get_empty_channel_id(struct cbd_transport *cbdt, u32 *id)
+{
+	int ret;
+
+	ret = cbdt_get_empty_segment_id(cbdt, id);
+	if (ret)
+		return ret;
+
+	channel_format(cbdt, *id);
+
+	return 0;
+}
+
+void cbdc_copy_to_bio(struct cbd_channel *channel,
+		u32 data_off, u32 data_len, struct bio *bio, u32 bio_off)
+{
+	cbds_copy_to_bio(&channel->segment, data_off, data_len, bio, bio_off);
+}
+
+void cbdc_copy_from_bio(struct cbd_channel *channel,
+		u32 data_off, u32 data_len, struct bio *bio, u32 bio_off)
+{
+	cbds_copy_from_bio(&channel->segment, data_off, data_len, bio, bio_off);
+}
+
+u32 cbd_channel_crc(struct cbd_channel *channel, u32 data_off, u32 data_len)
+{
+	return cbd_seg_crc(&channel->segment, data_off, data_len);
+}
+
+
+int cbdc_map_pages(struct cbd_channel *channel, struct cbd_backend_io *io)
+{
+	return cbds_map_pages(&channel->segment, io);
+}
+
+ssize_t cbd_channel_seg_detail_show(struct cbd_channel_info *channel_info, char *buf)
+{
+	return sprintf(buf, "channel backend id: %u\n"
+			"channel blkdev id: %u\n",
+			channel_info->backend_id,
+			channel_info->blkdev_id);
+}
+
+static void cbd_channel_seg_sanitize_pos(struct cbd_seg_pos *pos)
+{
+	struct cbd_segment *segment = pos->segment;
+
+	/* channel only use one segment as a ring */
+	while (pos->off >= segment->data_size)
+		pos->off -= segment->data_size;
+}
+
+static struct cbd_seg_ops cbd_channel_seg_ops = {
+	.sanitize_pos = cbd_channel_seg_sanitize_pos
+};
+
+void cbd_channel_init(struct cbd_channel *channel, struct cbd_transport *cbdt, u32 seg_id)
+{
+	struct cbd_channel_info *channel_info = cbdt_get_channel_info(cbdt, seg_id);
+	struct cbd_segment *segment = &channel->segment;
+	struct cbds_init_options seg_options;
+
+	seg_options.seg_id = seg_id;
+	seg_options.type = cbds_type_channel;
+	seg_options.data_off = CBDC_DATA_OFF;
+	seg_options.seg_ops = &cbd_channel_seg_ops;
+
+	cbd_segment_init(cbdt, segment, &seg_options);
+
+	channel->cbdt = cbdt;
+	channel->channel_info = channel_info;
+	channel->seg_id = seg_id;
+	channel->submr = (void *)channel_info + CBDC_SUBMR_OFF;
+	channel->compr = (void *)channel_info + CBDC_COMPR_OFF;
+	channel->submr_size = rounddown(CBDC_SUBMR_SIZE, sizeof(struct cbd_se));
+	channel->compr_size = rounddown(CBDC_COMPR_SIZE, sizeof(struct cbd_ce));
+	channel->data_size = CBDC_DATA_SIZE;
+
+	spin_lock_init(&channel->submr_lock);
+	spin_lock_init(&channel->compr_lock);
+}
+
+void cbd_channel_exit(struct cbd_channel *channel)
+{
+	cbd_segment_exit(&channel->segment);
+}
-- 
2.34.1