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Date: Mon, 2 Mar 2020 16:34:23 +1100 From: Andrew Donnellan <ajd@...ux.ibm.com> To: "Alastair D'Silva" <alastair@....ibm.com>, alastair@...ilva.org Cc: "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>, "Oliver O'Halloran" <oohall@...il.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Michael Ellerman <mpe@...erman.id.au>, Frederic Barrat <fbarrat@...ux.ibm.com>, Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Dan Williams <dan.j.williams@...el.com>, Vishal Verma <vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>, Ira Weiny <ira.weiny@...el.com>, Andrew Morton <akpm@...ux-foundation.org>, Mauro Carvalho Chehab <mchehab+samsung@...nel.org>, "David S. Miller" <davem@...emloft.net>, Rob Herring <robh@...nel.org>, Anton Blanchard <anton@...abs.org>, Krzysztof Kozlowski <krzk@...nel.org>, Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>, Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>, Cédric Le Goater <clg@...d.org>, Anju T Sudhakar <anju@...ux.vnet.ibm.com>, Hari Bathini <hbathini@...ux.ibm.com>, Thomas Gleixner <tglx@...utronix.de>, Greg Kurz <groug@...d.org>, Nicholas Piggin <npiggin@...il.com>, Masahiro Yamada <yamada.masahiro@...ionext.com>, Alexey Kardashevskiy <aik@...abs.ru>, linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, linux-nvdimm@...ts.01.org, linux-mm@...ck.org Subject: Re: [PATCH v3 16/27] powerpc/powernv/pmem: Register a character device for userspace to interact with On 21/2/20 2:27 pm, Alastair D'Silva wrote: > From: Alastair D'Silva <alastair@...ilva.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@...ilva.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@...ux.ibm.com IBM Australia Limited
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