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Subject[PATCH v2 15/27] nvdimm/ocxl: Register a character device for userspace to interact with
Date
From: Alastair D'Silva <alastair@d-silva.org>

This patch introduces a character device (/dev/ocxl-scmX) which further
patches will use to interact with userspace.

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
---
drivers/nvdimm/ocxl/scm.c | 114 ++++++++++++++++++++++++++++-
drivers/nvdimm/ocxl/scm_internal.h | 2 +
2 files changed, 115 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/ocxl/scm.c b/drivers/nvdimm/ocxl/scm.c
index 6c16ca7fabfa..c313a473a28e 100644
--- a/drivers/nvdimm/ocxl/scm.c
+++ b/drivers/nvdimm/ocxl/scm.c
@@ -9,6 +9,7 @@
#include <misc/ocxl.h>
#include <linux/delay.h>
#include <linux/ndctl.h>
+#include <linux/fs.h>
#include <linux/mm_types.h>
#include <linux/memory_hotplug.h>
#include "scm_internal.h"
@@ -386,6 +387,9 @@ static void free_scm(struct scm_data *scm_data)

free_scm_minor(scm_data);

+ if (scm_data->cdev.owner)
+ cdev_del(&scm_data->cdev);
+
if (scm_data->metadata_addr)
devm_memunmap(&scm_data->dev, scm_data->metadata_addr);

@@ -444,6 +448,70 @@ static int scm_register(struct scm_data *scm_data)
return rc;
}

+static void scm_put(struct scm_data *scm_data)
+{
+ put_device(&scm_data->dev);
+}
+
+static struct scm_data *scm_get(struct scm_data *scm_data)
+{
+ return (get_device(&scm_data->dev) == NULL) ? NULL : scm_data;
+}
+
+static struct scm_data *find_and_get_scm(dev_t devno)
+{
+ struct scm_data *scm_data;
+ int minor = MINOR(devno);
+ /*
+ * We don't declare an RCU critical section here, as our AFU
+ * is protected by a reference counter on the device. By the time the
+ * minor number of a device is removed from the idr, the ref count of
+ * the device is already at 0, so no user API will access that AFU and
+ * this function can't return it.
+ */
+ scm_data = idr_find(&minors_idr, minor);
+ if (scm_data)
+ scm_get(scm_data);
+ return scm_data;
+}
+
+static int scm_file_open(struct inode *inode, struct file *file)
+{
+ struct scm_data *scm_data;
+
+ scm_data = find_and_get_scm(inode->i_rdev);
+ if (!scm_data)
+ return -ENODEV;
+
+ file->private_data = scm_data;
+ return 0;
+}
+
+static int scm_file_release(struct inode *inode, struct file *file)
+{
+ struct scm_data *scm_data = file->private_data;
+
+ scm_put(scm_data);
+ return 0;
+}
+
+static const struct file_operations scm_fops = {
+ .owner = THIS_MODULE,
+ .open = scm_file_open,
+ .release = scm_file_release,
+};
+
+/**
+ * scm_create_cdev() - Create the chardev in /dev for this scm device
+ * @scm_data: the SCM metadata
+ * Return: 0 on success, negative on failure
+ */
+static int scm_create_cdev(struct scm_data *scm_data)
+{
+ cdev_init(&scm_data->cdev, &scm_fops);
+ return cdev_add(&scm_data->cdev, scm_data->dev.devt, 1);
+}
+
/**
* scm_remove() - Free an OpenCAPI Storage Class Memory device
* @pdev: the PCI device information struct
@@ -616,6 +684,11 @@ static int scm_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
goto err;
}

+ if (scm_create_cdev(scm_data)) {
+ dev_err(&pdev->dev, "Could not create SCM character device\n");
+ goto err;
+ }
+
elapsed = 0;
timeout = scm_data->readiness_timeout + scm_data->memory_available_timeout;
while (!scm_is_usable(scm_data)) {
@@ -653,20 +726,59 @@ static struct pci_driver scm_pci_driver = {
.shutdown = scm_remove,
};

+static int scm_file_init(void)
+{
+ int rc;
+
+ mutex_init(&minors_idr_lock);
+ idr_init(&minors_idr);
+
+ rc = alloc_chrdev_region(&scm_dev, 0, SCM_NUM_MINORS, "ocxl-scm");
+ if (rc) {
+ idr_destroy(&minors_idr);
+ pr_err("Unable to allocate scm major number: %d\n", rc);
+ return rc;
+ }
+
+ scm_class = class_create(THIS_MODULE, "ocxl-scm");
+ if (IS_ERR(scm_class)) {
+ idr_destroy(&minors_idr);
+ pr_err("Unable to create ocxl-scm class\n");
+ unregister_chrdev_region(scm_dev, SCM_NUM_MINORS);
+ return PTR_ERR(scm_class);
+ }
+
+ return 0;
+}
+
+static void scm_file_exit(void)
+{
+ class_destroy(scm_class);
+ unregister_chrdev_region(scm_dev, SCM_NUM_MINORS);
+ idr_destroy(&minors_idr);
+}
+
static int __init scm_init(void)
{
int rc = 0;

- rc = pci_register_driver(&scm_pci_driver);
+ rc = scm_file_init();
if (rc)
return rc;

+ rc = pci_register_driver(&scm_pci_driver);
+ if (rc) {
+ scm_file_exit();
+ return rc;
+ }
+
return 0;
}

static void scm_exit(void)
{
pci_unregister_driver(&scm_pci_driver);
+ scm_file_exit();
}

module_init(scm_init);
diff --git a/drivers/nvdimm/ocxl/scm_internal.h b/drivers/nvdimm/ocxl/scm_internal.h
index 9575996a89e7..57491dbee1a4 100644
--- a/drivers/nvdimm/ocxl/scm_internal.h
+++ b/drivers/nvdimm/ocxl/scm_internal.h
@@ -2,6 +2,7 @@
// Copyright 2019 IBM Corp.

#include <linux/pci.h>
+#include <linux/cdev.h>
#include <misc/ocxl.h>
#include <linux/libnvdimm.h>
#include <linux/mm.h>
@@ -100,6 +101,7 @@ struct scm_function_0 {
struct scm_data {
struct device dev;
struct pci_dev *pdev;
+ struct cdev cdev;
struct ocxl_fn *ocxl_fn;
struct nd_interleave_set nd_set;
struct nvdimm_bus_descriptor bus_desc;
--
2.23.0
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