On 2/6/25 5:13 PM, Jason Gunthorpe wrote: > Each file descriptor gets a chunk of per-FD driver specific context that > allows the driver to attach a device specific struct to. The core code > takes care of the memory lifetime for this structure. > > The ioctl dispatch and design is based on what was built for iommufd. The > ioctls have a struct which has a combined in/out behavior with a typical > 'zero pad' scheme for future extension and backwards compatibility. > > Like iommufd some shared logic does most of the ioctl marshalling and s/marshalling/marshaling/ > compatibility work and tables diatches to some function pointers for s/diatches/dispatches/ > each unique iotcl. s/iotcl/ioctl/ > > This approach has proven to work quite well in the iommufd and rdma > subsystems. > > Allocate an ioctl number space for the subsystem. > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx> > --- > .../userspace-api/ioctl/ioctl-number.rst | 1 + > MAINTAINERS | 1 + > drivers/fwctl/main.c | 145 +++++++++++++++++- > include/linux/fwctl.h | 46 ++++++ > include/uapi/fwctl/fwctl.h | 38 +++++ > 5 files changed, 226 insertions(+), 5 deletions(-) > create mode 100644 include/uapi/fwctl/fwctl.h > > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst > index 6d1465315df328..3410b020a9d093 100644 > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst > @@ -331,6 +331,7 @@ Code Seq# Include File Comments > 0x97 00-7F fs/ceph/ioctl.h Ceph file system > 0x99 00-0F 537-Addinboard driver > <mailto:buk@xxxxxxxxxxx> > +0x9A 00-0F include/uapi/fwctl/fwctl.h > 0xA0 all linux/sdp/sdp.h Industrial Device Project > <mailto:kenji@xxxxxxxxxxx> > 0xA1 0 linux/vtpm_proxy.h TPM Emulator Proxy Driver > diff --git a/MAINTAINERS b/MAINTAINERS > index ff418a77f39e4d..5f30adbe6c8521 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -9564,6 +9564,7 @@ S: Maintained > F: Documentation/userspace-api/fwctl.rst > F: drivers/fwctl/ > F: include/linux/fwctl.h > +F: include/uapi/fwctl/ > > GALAXYCORE GC0308 CAMERA SENSOR DRIVER > M: Sebastian Reichel <sre@xxxxxxxxxx> > diff --git a/drivers/fwctl/main.c b/drivers/fwctl/main.c > index 34946bdc3bf3d7..d561deaf2b86d8 100644 > --- a/drivers/fwctl/main.c > +++ b/drivers/fwctl/main.c > @@ -10,6 +10,8 @@ > #include <linux/module.h> > #include <linux/slab.h> > > +#include <uapi/fwctl/fwctl.h> > + > enum { > FWCTL_MAX_DEVICES = 4096, > }; > @@ -18,20 +20,128 @@ static_assert(FWCTL_MAX_DEVICES < (1U << MINORBITS)); > static dev_t fwctl_dev; > static DEFINE_IDA(fwctl_ida); > > +struct fwctl_ucmd { > + struct fwctl_uctx *uctx; > + void __user *ubuffer; > + void *cmd; > + u32 user_size; > +}; > + > +/* On stack memory for the ioctl structs */ > +union ucmd_buffer { > +}; > + > +struct fwctl_ioctl_op { > + unsigned int size; > + unsigned int min_size; > + unsigned int ioctl_num; > + int (*execute)(struct fwctl_ucmd *ucmd); > +}; > + > +#define IOCTL_OP(_ioctl, _fn, _struct, _last) \ > + [_IOC_NR(_ioctl) - FWCTL_CMD_BASE] = { \ > + .size = sizeof(_struct) + \ > + BUILD_BUG_ON_ZERO(sizeof(union ucmd_buffer) < \ > + sizeof(_struct)), \ > + .min_size = offsetofend(_struct, _last), \ > + .ioctl_num = _ioctl, \ > + .execute = _fn, \ > + } > +static const struct fwctl_ioctl_op fwctl_ioctl_ops[] = { > +}; > + > +static long fwctl_fops_ioctl(struct file *filp, unsigned int cmd, > + unsigned long arg) > +{ > + struct fwctl_uctx *uctx = filp->private_data; > + const struct fwctl_ioctl_op *op; > + struct fwctl_ucmd ucmd = {}; > + union ucmd_buffer buf; > + unsigned int nr; > + int ret; > + > + nr = _IOC_NR(cmd); > + if ((nr - FWCTL_CMD_BASE) >= ARRAY_SIZE(fwctl_ioctl_ops)) > + return -ENOIOCTLCMD; > + > + op = &fwctl_ioctl_ops[nr - FWCTL_CMD_BASE]; > + if (op->ioctl_num != cmd) > + return -ENOIOCTLCMD; > + > + ucmd.uctx = uctx; > + ucmd.cmd = &buf; > + ucmd.ubuffer = (void __user *)arg; > + ret = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer); > + if (ret) > + return ret; > + > + if (ucmd.user_size < op->min_size) > + return -EINVAL; > + > + ret = copy_struct_from_user(ucmd.cmd, op->size, ucmd.ubuffer, > + ucmd.user_size); > + if (ret) > + return ret; > + > + guard(rwsem_read)(&uctx->fwctl->registration_lock); > + if (!uctx->fwctl->ops) > + return -ENODEV; > + return op->execute(&ucmd); > +} > + > static int fwctl_fops_open(struct inode *inode, struct file *filp) > { > struct fwctl_device *fwctl = > container_of(inode->i_cdev, struct fwctl_device, cdev); > + int ret; > + > + guard(rwsem_read)(&fwctl->registration_lock); > + if (!fwctl->ops) > + return -ENODEV; > + > + struct fwctl_uctx *uctx __free(kfree) = > + kzalloc(fwctl->ops->uctx_size, GFP_KERNEL_ACCOUNT); > + if (!uctx) > + return -ENOMEM; > + > + uctx->fwctl = fwctl; > + ret = fwctl->ops->open_uctx(uctx); > + if (ret) > + return ret; > + > + scoped_guard(mutex, &fwctl->uctx_list_lock) { > + list_add_tail(&uctx->uctx_list_entry, &fwctl->uctx_list); > + } > > get_device(&fwctl->dev); > - filp->private_data = fwctl; > + filp->private_data = no_free_ptr(uctx); > return 0; > } > > +static void fwctl_destroy_uctx(struct fwctl_uctx *uctx) > +{ > + lockdep_assert_held(&uctx->fwctl->uctx_list_lock); > + list_del(&uctx->uctx_list_entry); > + uctx->fwctl->ops->close_uctx(uctx); > +} > + > static int fwctl_fops_release(struct inode *inode, struct file *filp) > { > - struct fwctl_device *fwctl = filp->private_data; > + struct fwctl_uctx *uctx = filp->private_data; > + struct fwctl_device *fwctl = uctx->fwctl; > > + scoped_guard(rwsem_read, &fwctl->registration_lock) { > + /* > + * fwctl_unregister() has already removed the driver and > + * destroyed the uctx. > + */ > + if (fwctl->ops) { > + guard(mutex)(&fwctl->uctx_list_lock); > + fwctl_destroy_uctx(uctx); > + } > + } > + > + kfree(uctx); > fwctl_put(fwctl); > return 0; > } > @@ -40,6 +150,7 @@ static const struct file_operations fwctl_fops = { > .owner = THIS_MODULE, > .open = fwctl_fops_open, > .release = fwctl_fops_release, > + .unlocked_ioctl = fwctl_fops_ioctl, > }; > > static void fwctl_device_release(struct device *device) > @@ -48,6 +159,7 @@ static void fwctl_device_release(struct device *device) > container_of(device, struct fwctl_device, dev); > > ida_free(&fwctl_ida, fwctl->dev.devt - fwctl_dev); > + mutex_destroy(&fwctl->uctx_list_lock); > kfree(fwctl); > } > > @@ -71,14 +183,17 @@ _alloc_device(struct device *parent, const struct fwctl_ops *ops, size_t size) > if (!fwctl) > return NULL; > > - fwctl->dev.class = &fwctl_class; > - fwctl->dev.parent = parent; > - > devnum = ida_alloc_max(&fwctl_ida, FWCTL_MAX_DEVICES - 1, GFP_KERNEL); > if (devnum < 0) > return NULL; > fwctl->dev.devt = fwctl_dev + devnum; > > + fwctl->dev.class = &fwctl_class; > + fwctl->dev.parent = parent; > + init_rwsem(&fwctl->registration_lock); > + mutex_init(&fwctl->uctx_list_lock); > + INIT_LIST_HEAD(&fwctl->uctx_list); > + > device_initialize(&fwctl->dev); > return_ptr(fwctl); > } > @@ -129,6 +244,10 @@ EXPORT_SYMBOL_NS_GPL(fwctl_register, "FWCTL"); > * Undoes fwctl_register(). On return no driver ops will be called. The > * caller must still call fwctl_put() to free the fwctl. > * > + * Unregister will return even if userspace still has file descriptors open. > + * This will call ops->close_uctx() on any open FDs and after return no driver > + * op will be called. The FDs remain open but all fops will return -ENODEV. > + * > * The design of fwctl allows this sort of disassociation of the driver from the > * subsystem primarily by keeping memory allocations owned by the core subsytem. > * The fwctl_device and fwctl_uctx can both be freed without requiring a driver > @@ -136,7 +255,23 @@ EXPORT_SYMBOL_NS_GPL(fwctl_register, "FWCTL"); > */ > void fwctl_unregister(struct fwctl_device *fwctl) > { > + struct fwctl_uctx *uctx; > + > cdev_device_del(&fwctl->cdev, &fwctl->dev); > + > + /* Disable and free the driver's resources for any still open FDs. */ > + guard(rwsem_write)(&fwctl->registration_lock); > + guard(mutex)(&fwctl->uctx_list_lock); > + while ((uctx = list_first_entry_or_null(&fwctl->uctx_list, > + struct fwctl_uctx, > + uctx_list_entry))) > + fwctl_destroy_uctx(uctx); > + > + /* > + * The driver module may unload after this returns, the op pointer will > + * not be valid. > + */ > + fwctl->ops = NULL; > } > EXPORT_SYMBOL_NS_GPL(fwctl_unregister, "FWCTL"); > > diff --git a/include/linux/fwctl.h b/include/linux/fwctl.h > index 68ac2d5ab87481..93b470efb9dbc3 100644 > --- a/include/linux/fwctl.h > +++ b/include/linux/fwctl.h > @@ -11,7 +11,30 @@ > struct fwctl_device; > struct fwctl_uctx; > > +/** > + * struct fwctl_ops - Driver provided operations > + * > + * fwctl_unregister() will wait until all excuting ops are completed before it > + * returns. Drivers should be mindful to not let their ops run for too long as > + * it will block device hot unplug and module unloading. > + */ > struct fwctl_ops { > + /** > + * @uctx_size: The size of the fwctl_uctx struct to allocate. The first > + * bytes of this memory will be a fwctl_uctx. The driver can use the > + * remaining bytes as its private memory. > + */ > + size_t uctx_size; > + /** > + * @open_uctx: Called when a file descriptor is opened before the uctx > + * is ever used. > + */ > + int (*open_uctx)(struct fwctl_uctx *uctx); > + /** > + * @close_uctx: Called when the uctx is destroyed, usually when the FD > + * is closed. > + */ > + void (*close_uctx)(struct fwctl_uctx *uctx); > }; > > /** > @@ -26,6 +49,15 @@ struct fwctl_device { > struct device dev; > /* private: */ > struct cdev cdev; > + > + /* Protect uctx_list */ > + struct mutex uctx_list_lock; > + struct list_head uctx_list; > + /* > + * Protect ops, held for write when ops becomes NULL during unregister, > + * held for read whenever ops is loaded or an ops function is running. > + */ > + struct rw_semaphore registration_lock; > const struct fwctl_ops *ops; > }; > > @@ -66,4 +98,18 @@ DEFINE_FREE(fwctl, struct fwctl_device *, if (_T) fwctl_put(_T)); > int fwctl_register(struct fwctl_device *fwctl); > void fwctl_unregister(struct fwctl_device *fwctl); > > +/** > + * struct fwctl_uctx - Per user FD context > + * @fwctl: fwctl instance that owns the context > + * > + * Every FD opened by userspace will get a unique context allocation. Any driver > + * private data will follow immediately after. > + */ > +struct fwctl_uctx { > + struct fwctl_device *fwctl; > + /* private: */ > + /* Head at fwctl_device::uctx_list */ > + struct list_head uctx_list_entry; > +}; > + > #endif > diff --git a/include/uapi/fwctl/fwctl.h b/include/uapi/fwctl/fwctl.h > new file mode 100644 > index 00000000000000..f4718a6240f281 > --- /dev/null > +++ b/include/uapi/fwctl/fwctl.h > @@ -0,0 +1,38 @@ > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ > +/* Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES. > + */ > +#ifndef _UAPI_FWCTL_H > +#define _UAPI_FWCTL_H > + > +#define FWCTL_TYPE 0x9A > + > +/** > + * DOC: General ioctl format > + * > + * The ioctl interface follows a general format to allow for extensibility. Each > + * ioctl is passed a structure pointer as the argument providing the size of > + * the structure in the first u32. The kernel checks that any structure space > + * beyond what it understands is 0. This allows userspace to use the backward > + * compatible portion while consistently using the newer, larger, structures. > + * > + * ioctls use a standard meaning for common errnos: > + * > + * - ENOTTY: The IOCTL number itself is not supported at all > + * - E2BIG: The IOCTL number is supported, but the provided structure has > + * non-zero in a part the kernel does not understand. > + * - EOPNOTSUPP: The IOCTL number is supported, and the structure is > + * understood, however a known field has a value the kernel does not > + * understand or support. > + * - EINVAL: Everything about the IOCTL was understood, but a field is not > + * correct. > + * - ENOMEM: Out of memory. > + * - ENODEV: The underlying device has been hot-unplugged and the FD is > + * orphaned. > + * > + * As well as additional errnos, within specific ioctls. > + */ > +enum { > + FWCTL_CMD_BASE = 0, > +}; > + > +#endif
