linux-kernel - [PATCH RFC v2 02/18] scsi: core: Resurrect scsi_{get,free}_host

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Date:   Thu, 9 Jun 2022 18:29:03 +0800
From:   John Garry <john.garry@...wei.com>
To:     <axboe@...nel.dk>, <damien.lemoal@...nsource.wdc.com>,
        <jejb@...ux.ibm.com>, <martin.petersen@...cle.com>,
        <brking@...ibm.com>, <hare@...e.de>, <hch@....de>
CC:     <linux-block@...r.kernel.org>, <linux-ide@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        <chenxiang66@...ilicon.com>, John Garry <john.garry@...wei.com>
Subject: [PATCH RFC v2 02/18] scsi: core: Resurrect scsi_{get,free}_host_dev()

This reverts commit 6bd49b1a8d43ec118c55f3aaa7577729b52bde15.

Signed-off-by: John Garry <john.garry@...wei.com>
---
 drivers/scsi/scsi_scan.c | 57 ++++++++++++++++++++++++++++++++++++++++
 include/scsi/scsi_host.h | 10 +++++++
 2 files changed, 67 insertions(+)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 91ac901a6682..925fe63fa370 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1978,3 +1978,60 @@ void scsi_forget_host(struct Scsi_Host *shost)
 	spin_unlock_irqrestore(shost->host_lock, flags);
 }
 
+/**
+ * scsi_get_host_dev - Create a scsi_device that points to the host adapter itself
+ * @shost: Host that needs a scsi_device
+ *
+ * Lock status: None assumed.
+ *
+ * Returns:     The scsi_device or NULL
+ *
+ * Notes:
+ *	Attach a single scsi_device to the Scsi_Host - this should
+ *	be made to look like a "pseudo-device" that points to the
+ *	HA itself.
+ *
+ *	Note - this device is not accessible from any high-level
+ *	drivers (including generics), which is probably not
+ *	optimal.  We can add hooks later to attach.
+ */
+struct scsi_device *scsi_get_host_dev(struct Scsi_Host *shost)
+{
+	struct scsi_device *sdev = NULL;
+	struct scsi_target *starget;
+
+	mutex_lock(&shost->scan_mutex);
+	if (!scsi_host_scan_allowed(shost))
+		goto out;
+	starget = scsi_alloc_target(&shost->shost_gendev, 0, shost->this_id);
+	if (!starget)
+		goto out;
+
+	sdev = scsi_alloc_sdev(starget, 0, NULL);
+	if (sdev)
+		sdev->borken = 0;
+	else
+		scsi_target_reap(starget);
+	put_device(&starget->dev);
+ out:
+	mutex_unlock(&shost->scan_mutex);
+	return sdev;
+}
+EXPORT_SYMBOL(scsi_get_host_dev);
+
+/**
+ * scsi_free_host_dev - Free a scsi_device that points to the host adapter itself
+ * @sdev: Host device to be freed
+ *
+ * Lock status: None assumed.
+ *
+ * Returns:     Nothing
+ */
+void scsi_free_host_dev(struct scsi_device *sdev)
+{
+	BUG_ON(sdev->id != sdev->host->this_id);
+
+	__scsi_remove_device(sdev);
+}
+EXPORT_SYMBOL(scsi_free_host_dev);
+
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 667d889b92b5..59aef1f178f5 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -790,6 +790,16 @@ void scsi_host_busy_iter(struct Scsi_Host *,
 
 struct class_container;
 
+/*
+ * These two functions are used to allocate and free a pseudo device
+ * which will connect to the host adapter itself rather than any
+ * physical device.  You must deallocate when you are done with the
+ * thing.  This physical pseudo-device isn't real and won't be available
+ * from any high-level drivers.
+ */
+extern void scsi_free_host_dev(struct scsi_device *);
+extern struct scsi_device *scsi_get_host_dev(struct Scsi_Host *);
+
 /*
  * DIF defines the exchange of protection information between
  * initiator and SBC block device.
-- 
2.26.2