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SubjectRe: [PATCH v3 16/27] powerpc/powernv/pmem: Register a character device for userspace to interact with
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On 21/2/20 2:27 pm, Alastair D'Silva wrote:
> 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.

As with the comments on other patches in this series, this commit
message is lacking in explanation. What's the purpose of this device?

>
> Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
> ---
> arch/powerpc/platforms/powernv/pmem/ocxl.c | 116 +++++++++++++++++-
> .../platforms/powernv/pmem/ocxl_internal.h | 2 +
> 2 files changed, 116 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/pmem/ocxl.c b/arch/powerpc/platforms/powernv/pmem/ocxl.c
> index b8bd7e703b19..63109a870d2c 100644
> --- a/arch/powerpc/platforms/powernv/pmem/ocxl.c
> +++ b/arch/powerpc/platforms/powernv/pmem/ocxl.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 "ocxl_internal.h"
> @@ -339,6 +340,9 @@ static void free_ocxlpmem(struct ocxlpmem *ocxlpmem)
>
> free_minor(ocxlpmem);
>
> + if (ocxlpmem->cdev.owner)
> + cdev_del(&ocxlpmem->cdev);
> +
> if (ocxlpmem->metadata_addr)
> devm_memunmap(&ocxlpmem->dev, ocxlpmem->metadata_addr);
>
> @@ -396,6 +400,70 @@ 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) ? NULL : ocxlpmem;
> +}
> +
> +static struct ocxlpmem *find_and_get_ocxlpmem(dev_t devno)
> +{
> + struct ocxlpmem *ocxlpmem;
> + int minor = MINOR(devno);
> + /*
> + * We don't declare an RCU critical section here, as our AFU
> + * is protected by a re0ference 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.
> + */
> + ocxlpmem = idr_find(&minors_idr, minor);
> + if (ocxlpmem)
> + ocxlpmem_get(ocxlpmem);
> + 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
> @@ -572,6 +640,11 @@ static int probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> goto err;
> }
>
> + if (create_cdev(ocxlpmem)) {
> + dev_err(&pdev->dev, "Could not create character device\n");
> + goto err;
> + }
> +
> elapsed = 0;
> timeout = ocxlpmem->readiness_timeout + ocxlpmem->memory_available_timeout;
> while (!is_usable(ocxlpmem, false)) {
> @@ -613,20 +686,59 @@ static struct pci_driver pci_driver = {
> .shutdown = ocxlpmem_remove,
> };
>
> +static int file_init(void)
> +{
> + int rc;
> +
> + mutex_init(&minors_idr_lock);
> + idr_init(&minors_idr);
> +
> + rc = alloc_chrdev_region(&ocxlpmem_dev, 0, NUM_MINORS, "ocxl-pmem");

If the driver is going to be called "ocxlpmem" can we standardise on
that without the extra hyphen?

> + 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, "ocxl-pmem");
> + if (IS_ERR(ocxlpmem_class)) {
> + idr_destroy(&minors_idr);
> + pr_err("Unable to create ocxl-pmem 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 = 0;
> + int rc;
>
> - 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);
--
Andrew Donnellan OzLabs, ADL Canberra
ajd@linux.ibm.com IBM Australia Limited

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