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Subject[PATCH v4 15/25] nvdimm/ocxl: Register a character device for userspace to interact with
Date
This patch introduces a character device (/dev/ocxlpmemX) which further
patches will use to interact with userspace, such as error logs,
controller stats and card debug functionality.

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
---
drivers/nvdimm/ocxl/main.c | 117 ++++++++++++++++++++++++++++++++-
drivers/nvdimm/ocxl/ocxlpmem.h | 2 +
2 files changed, 117 insertions(+), 2 deletions(-)

diff --git a/drivers/nvdimm/ocxl/main.c b/drivers/nvdimm/ocxl/main.c
index 8db573036423..9b85fcd3f1c9 100644
--- a/drivers/nvdimm/ocxl/main.c
+++ b/drivers/nvdimm/ocxl/main.c
@@ -10,6 +10,7 @@
#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 "ocxlpmem.h"
@@ -356,6 +357,67 @@ static int ocxlpmem_register(struct ocxlpmem *ocxlpmem)
return device_register(&ocxlpmem->dev);
}

+static void ocxlpmem_put(struct ocxlpmem *ocxlpmem)
+{
+ put_device(&ocxlpmem->dev);
+}
+
+static struct ocxlpmem *ocxlpmem_get(struct ocxlpmem *ocxlpmem)
+{
+ return (!get_device(&ocxlpmem->dev)) ? NULL : ocxlpmem;
+}
+
+static struct ocxlpmem *find_and_get_ocxlpmem(dev_t devno)
+{
+ struct ocxlpmem *ocxlpmem;
+ int minor = MINOR(devno);
+
+ mutex_lock(&minors_idr_lock);
+ ocxlpmem = idr_find(&minors_idr, minor);
+ if (ocxlpmem)
+ ocxlpmem_get(ocxlpmem);
+ mutex_unlock(&minors_idr_lock);
+
+ return ocxlpmem;
+}
+
+static int file_open(struct inode *inode, struct file *file)
+{
+ struct ocxlpmem *ocxlpmem;
+
+ ocxlpmem = find_and_get_ocxlpmem(inode->i_rdev);
+ if (!ocxlpmem)
+ return -ENODEV;
+
+ file->private_data = ocxlpmem;
+ return 0;
+}
+
+static int file_release(struct inode *inode, struct file *file)
+{
+ struct ocxlpmem *ocxlpmem = file->private_data;
+
+ ocxlpmem_put(ocxlpmem);
+ return 0;
+}
+
+static const struct file_operations fops = {
+ .owner = THIS_MODULE,
+ .open = file_open,
+ .release = file_release,
+};
+
+/**
+ * create_cdev() - Create the chardev in /dev for the device
+ * @ocxlpmem: the SCM metadata
+ * Return: 0 on success, negative on failure
+ */
+static int create_cdev(struct ocxlpmem *ocxlpmem)
+{
+ cdev_init(&ocxlpmem->cdev, &fops);
+ return cdev_add(&ocxlpmem->cdev, ocxlpmem->dev.devt, 1);
+}
+
/**
* ocxlpmem_remove() - Free an OpenCAPI persistent memory device
* @pdev: the PCI device information struct
@@ -376,6 +438,13 @@ static void remove(struct pci_dev *pdev)
if (ocxlpmem->nvdimm_bus)
nvdimm_bus_unregister(ocxlpmem->nvdimm_bus);

+ /*
+ * Remove the cdev early to prevent a race against userspace
+ * via the char dev
+ */
+ if (ocxlpmem->cdev.owner)
+ cdev_del(&ocxlpmem->cdev);
+
device_unregister(&ocxlpmem->dev);
}
}
@@ -527,11 +596,18 @@ static int probe(struct pci_dev *pdev, const struct pci_device_id *ent)
goto err;
}

- if (setup_command_metadata(ocxlpmem)) {
+ rc = setup_command_metadata(ocxlpmem);
+ if (rc) {
dev_err(&pdev->dev, "Could not read command metadata\n");
goto err;
}

+ rc = create_cdev(ocxlpmem);
+ if (rc) {
+ dev_err(&pdev->dev, "Could not create character device\n");
+ goto err;
+ }
+
elapsed = 0;
timeout = ocxlpmem->readiness_timeout +
ocxlpmem->memory_available_timeout;
@@ -599,6 +675,36 @@ static struct pci_driver pci_driver = {
.shutdown = remove,
};

+static int file_init(void)
+{
+ int rc;
+
+ rc = alloc_chrdev_region(&ocxlpmem_dev, 0, NUM_MINORS, "ocxlpmem");
+ if (rc) {
+ idr_destroy(&minors_idr);
+ pr_err("Unable to allocate OpenCAPI persistent memory major number: %d\n",
+ rc);
+ return rc;
+ }
+
+ ocxlpmem_class = class_create(THIS_MODULE, "ocxlpmem");
+ if (IS_ERR(ocxlpmem_class)) {
+ idr_destroy(&minors_idr);
+ pr_err("Unable to create ocxlpmem class\n");
+ unregister_chrdev_region(ocxlpmem_dev, NUM_MINORS);
+ return PTR_ERR(ocxlpmem_class);
+ }
+
+ return 0;
+}
+
+static void file_exit(void)
+{
+ class_destroy(ocxlpmem_class);
+ unregister_chrdev_region(ocxlpmem_dev, NUM_MINORS);
+ idr_destroy(&minors_idr);
+}
+
static int __init ocxlpmem_init(void)
{
int rc;
@@ -606,16 +712,23 @@ static int __init ocxlpmem_init(void)
mutex_init(&minors_idr_lock);
idr_init(&minors_idr);

- rc = pci_register_driver(&pci_driver);
+ rc = file_init();
if (rc)
return rc;

+ rc = pci_register_driver(&pci_driver);
+ if (rc) {
+ file_exit();
+ return rc;
+ }
+
return 0;
}

static void ocxlpmem_exit(void)
{
pci_unregister_driver(&pci_driver);
+ file_exit();
}

module_init(ocxlpmem_init);
diff --git a/drivers/nvdimm/ocxl/ocxlpmem.h b/drivers/nvdimm/ocxl/ocxlpmem.h
index b72b3f909fc3..ee3bd651f254 100644
--- a/drivers/nvdimm/ocxl/ocxlpmem.h
+++ b/drivers/nvdimm/ocxl/ocxlpmem.h
@@ -2,6 +2,7 @@
// Copyright 2020 IBM Corp.

#include <linux/pci.h>
+#include <linux/cdev.h>
#include <misc/ocxl.h>
#include <linux/libnvdimm.h>
#include <linux/mm.h>
@@ -103,6 +104,7 @@ struct command_metadata {
struct ocxlpmem {
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;
--
2.24.1
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