Re: [PATCH RFC v2 02/18] scsi: core: Resurrect scsi_{get,free}_host_dev()

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On 6/9/22 03:29, John Garry wrote:
+/**
+ * scsi_get_host_dev - Create a scsi_device that points to the host adapter itself
                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
What does this mean? That part of the function description is not
clear to me.

+ * @shost: Host that needs a scsi_device
                              ^^^^^^^^^^^^^
This is not detailed enough. Consider changing "a scsi_device" into
"a scsi device for allocating reserved commands from".

+ *
+ * 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.

The "which is probably not optimal. We can add hooks later to attach."
part probably should be moved to the patch description.

+ */
+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);
                                                          ^^^^^^^^^^^^^^^^^^
Is it guaranteed that this channel / id combination will not be used for
any other SCSI device?

What if shost->this_id == -1?

+	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);

Elsewhere in the SCSI core "get..dev" means increment the reference count of
a SCSI device. Maybe scsi_alloc_host_dev() is a better name?

+/*
+ * 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.
+ */

Please keep function comments in .c files because that makes it more likely
that the comment and the implementation will remain in sync.

Thanks,

Bart.



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