scsi: ufs: Add a bsg endpoint that supports UPIUs

For now, just provide an API to allocate and remove ufs-bsg node. We
will use this framework to manage ufs devices by sending UPIU
transactions.

For the time being, implements an empty bsg_request() - will add some
more functionality in coming patches.

Nonetheless, we reveal here the protocol we are planning to use: UFS
Transport Protocol Transactions. UFS transactions consist of packets
called UFS Protocol Information Units (UPIU).

There are UPIU’s defined for UFS SCSI commands, responses, data in and
data out, task management, utility functions, vendor functions,
transaction synchronization and control, and more.

By using UPIUs, we get access to the most fine-grained internals of this
protocol, and able to communicate with the device in ways, that are
sometimes beyond the capacity of the ufs driver.

Moreover and as a result, our core structure - ufs_bsg_node has a pretty
lean structure: using upiu transactions that contains the outmost
detailed info, so we don't really need complex constructs to support it.

Signed-off-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <Bart.VanAssche@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 93 insertions, 0 deletions

diff --git a/drivers/scsi/ufs/ufs_bsg.c b/drivers/scsi/ufs/ufs_bsg.c
new file mode 100644
index 000000000000..1036c520d349
--- /dev/null
+++ b/drivers/scsi/ufs/ufs_bsg.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * bsg endpoint that supports UPIUs
+ *
+ * Copyright (C) 2018 Western Digital Corporation
+ */
+#include "ufs_bsg.h"
+
+
+static int ufs_bsg_request(struct bsg_job *job)
+{
+	struct ufs_bsg_request *bsg_request = job->request;
+	struct ufs_bsg_reply *bsg_reply = job->reply;
+	int ret = -ENOTSUPP;
+
+	bsg_reply->reply_payload_rcv_len = 0;
+
+	/* Do Nothing for now */
+	dev_err(job->dev, "unsupported message_code 0x%x\n",
+		bsg_request->msgcode);
+
+	bsg_reply->result = ret;
+	job->reply_len = sizeof(struct ufs_bsg_reply) +
+			 bsg_reply->reply_payload_rcv_len;
+
+	bsg_job_done(job, ret, bsg_reply->reply_payload_rcv_len);
+
+	return ret;
+}
+
+/**
+ * ufs_bsg_remove - detach and remove the added ufs-bsg node
+ *
+ * Should be called when unloading the driver.
+ */
+void ufs_bsg_remove(struct ufs_hba *hba)
+{
+	struct device *bsg_dev = &hba->bsg_dev;
+
+	if (!hba->bsg_queue)
+		return;
+
+	bsg_unregister_queue(hba->bsg_queue);
+
+	device_del(bsg_dev);
+	put_device(bsg_dev);
+}
+
+static inline void ufs_bsg_node_release(struct device *dev)
+{
+	put_device(dev->parent);
+}
+
+/**
+ * ufs_bsg_probe - Add ufs bsg device node
+ * @hba: per adapter object
+ *
+ * Called during initial loading of the driver, and before scsi_scan_host.
+ */
+int ufs_bsg_probe(struct ufs_hba *hba)
+{
+	struct device *bsg_dev = &hba->bsg_dev;
+	struct Scsi_Host *shost = hba->host;
+	struct device *parent = &shost->shost_gendev;
+	struct request_queue *q;
+	int ret;
+
+	device_initialize(bsg_dev);
+
+	bsg_dev->parent = get_device(parent);
+	bsg_dev->release = ufs_bsg_node_release;
+
+	dev_set_name(bsg_dev, "ufs-bsg");
+
+	ret = device_add(bsg_dev);
+	if (ret)
+		goto out;
+
+	q = bsg_setup_queue(bsg_dev, dev_name(bsg_dev), ufs_bsg_request, 0);
+	if (IS_ERR(q)) {
+		ret = PTR_ERR(q);
+		goto out;
+	}
+
+	hba->bsg_queue = q;
+
+	return 0;
+
+out:
+	dev_err(bsg_dev, "fail to initialize a bsg dev %d\n", shost->host_no);
+	put_device(bsg_dev);
+	return ret;
+}