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Date:   Fri, 22 Mar 2019 18:38:26 +0100
From:   Frederic Barrat <fbarrat@...ux.ibm.com>
To:     "Alastair D'Silva" <alastair@....ibm.com>, alastair@...ilva.org
Cc:     Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 3/7] ocxl: Create a clear delineation between ocxl
 backend & frontend

Hi Alastair,

I'm still seeing problems with the handling of the info structure and 
ref counting on the AFU. To make things easier, I'm attaching a patch. 
There's also a bunch of other review comments in the patch, check for 
the comments with the "fxb" marker.

I've played a bit with driver unload and force unbinds and the free 
operations were happening as expected. We're getting there!

   Fred


Le 20/03/2019 à 06:08, Alastair D'Silva a écrit :
> From: Alastair D'Silva <alastair@...ilva.org>
> 
> The OCXL driver contains both frontend code for interacting with userspace,
> as well as backend code for interacting with the hardware.
> 
> This patch separates the backend code from the frontend so that it can be
> used by other device drivers that communicate via OpenCAPI.
> 
> Relocate dev, cdev & sysfs files to the frontend code to allow external
> drivers to maintain their own devices.
> 
> Reference counting on the device in the backend is replaced with kref
> counting.
> 
> Move file & sysfs layer initialisation from core.c (backend) to
> pci.c (frontend).
> 
> Create an ocxl_function oriented interface for initing devices &
> enumerating AFUs.
> 
> Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
> ---
>   drivers/misc/ocxl/context.c       |   2 +-
>   drivers/misc/ocxl/core.c          | 205 +++++++++++++++++++-----------
>   drivers/misc/ocxl/file.c          | 125 ++++++++++++------
>   drivers/misc/ocxl/ocxl_internal.h |  39 +++---
>   drivers/misc/ocxl/pci.c           |  61 ++++-----
>   drivers/misc/ocxl/sysfs.c         |  58 +++++----
>   include/misc/ocxl.h               | 121 ++++++++++++++++--
>   7 files changed, 416 insertions(+), 195 deletions(-)
> 
> diff --git a/drivers/misc/ocxl/context.c b/drivers/misc/ocxl/context.c
> index 3498a0199bde..371ef17bba33 100644
> --- a/drivers/misc/ocxl/context.c
> +++ b/drivers/misc/ocxl/context.c
> @@ -238,7 +238,7 @@ int ocxl_context_detach(struct ocxl_context *ctx)
>   	}
>   	rc = ocxl_link_remove_pe(ctx->afu->fn->link, ctx->pasid);
>   	if (rc) {
> -		dev_warn(&ctx->afu->dev,
> +		dev_warn(&dev->dev,
>   			"Couldn't remove PE entry cleanly: %d\n", rc);
>   	}
>   	return 0;
> diff --git a/drivers/misc/ocxl/core.c b/drivers/misc/ocxl/core.c
> index 2fd0c700e8a0..c632ec372342 100644
> --- a/drivers/misc/ocxl/core.c
> +++ b/drivers/misc/ocxl/core.c
> @@ -13,16 +13,6 @@ static void ocxl_fn_put(struct ocxl_fn *fn)
>   	put_device(&fn->dev);
>   }
>   
> -struct ocxl_afu *ocxl_afu_get(struct ocxl_afu *afu)
> -{
> -	return (get_device(&afu->dev) == NULL) ? NULL : afu;
> -}
> -
> -void ocxl_afu_put(struct ocxl_afu *afu)
> -{
> -	put_device(&afu->dev);
> -}
> -
>   static struct ocxl_afu *alloc_afu(struct ocxl_fn *fn)
>   {
>   	struct ocxl_afu *afu;
> @@ -31,6 +21,7 @@ static struct ocxl_afu *alloc_afu(struct ocxl_fn *fn)
>   	if (!afu)
>   		return NULL;
>   
> +	kref_init(&afu->kref);
>   	mutex_init(&afu->contexts_lock);
>   	mutex_init(&afu->afu_control_lock);
>   	idr_init(&afu->contexts_idr);
> @@ -39,32 +30,26 @@ static struct ocxl_afu *alloc_afu(struct ocxl_fn *fn)
>   	return afu;
>   }
>   
> -static void free_afu(struct ocxl_afu *afu)
> +static void afu_release(struct kref *kref)
>   {
> +	struct ocxl_afu *afu = container_of(kref, struct ocxl_afu, kref);
> +
>   	idr_destroy(&afu->contexts_idr);
>   	ocxl_fn_put(afu->fn);
>   	kfree(afu);
>   }
>   
> -static void free_afu_dev(struct device *dev)
> +void ocxl_afu_get(struct ocxl_afu *afu)
>   {
> -	struct ocxl_afu *afu = to_ocxl_afu(dev);
> -
> -	ocxl_unregister_afu(afu);
> -	free_afu(afu);
> +	kref_get(&afu->kref);
>   }
> +EXPORT_SYMBOL_GPL(ocxl_afu_get);
>   
> -static int set_afu_device(struct ocxl_afu *afu, const char *location)
> +void ocxl_afu_put(struct ocxl_afu *afu)
>   {
> -	struct ocxl_fn *fn = afu->fn;
> -	int rc;
> -
> -	afu->dev.parent = &fn->dev;
> -	afu->dev.release = free_afu_dev;
> -	rc = dev_set_name(&afu->dev, "%s.%s.%hhu", afu->config.name, location,
> -		afu->config.idx);
> -	return rc;
> +	kref_put(&afu->kref, afu_release);
>   }
> +EXPORT_SYMBOL_GPL(ocxl_afu_put);
>   
>   static int assign_afu_actag(struct ocxl_afu *afu)
>   {
> @@ -233,27 +218,25 @@ static int configure_afu(struct ocxl_afu *afu, u8 afu_idx, struct pci_dev *dev)
>   	if (rc)
>   		return rc;
>   
> -	rc = set_afu_device(afu, dev_name(&dev->dev));
> -	if (rc)
> -		return rc;
> -
>   	rc = assign_afu_actag(afu);
>   	if (rc)
>   		return rc;
>   
>   	rc = assign_afu_pasid(afu);
> -	if (rc) {
> -		reclaim_afu_actag(afu);
> -		return rc;
> -	}
> +	if (rc)
> +		goto err_free_actag;
>   
>   	rc = map_mmio_areas(afu);
> -	if (rc) {
> -		reclaim_afu_pasid(afu);
> -		reclaim_afu_actag(afu);
> -		return rc;
> -	}
> +	if (rc)
> +		goto err_free_pasid;
> +
>   	return 0;
> +
> +err_free_pasid:
> +	reclaim_afu_pasid(afu);
> +err_free_actag:
> +	reclaim_afu_actag(afu);
> +	return rc;
>   }
>   
>   static void deconfigure_afu(struct ocxl_afu *afu)
> @@ -265,16 +248,8 @@ static void deconfigure_afu(struct ocxl_afu *afu)
>   
>   static int activate_afu(struct pci_dev *dev, struct ocxl_afu *afu)
>   {
> -	int rc;
> -
>   	ocxl_config_set_afu_state(dev, afu->config.dvsec_afu_control_pos, 1);
> -	/*
> -	 * Char device creation is the last step, as processes can
> -	 * call our driver immediately, so all our inits must be finished.
> -	 */
> -	rc = ocxl_create_cdev(afu);
> -	if (rc)
> -		return rc;
> +
>   	return 0;
>   }
>   
> @@ -282,11 +257,10 @@ static void deactivate_afu(struct ocxl_afu *afu)
>   {
>   	struct pci_dev *dev = to_pci_dev(afu->fn->dev.parent);
>   
> -	ocxl_destroy_cdev(afu);
>   	ocxl_config_set_afu_state(dev, afu->config.dvsec_afu_control_pos, 0);
>   }
>   
> -int init_afu(struct pci_dev *dev, struct ocxl_fn *fn, u8 afu_idx)
> +static int init_afu(struct pci_dev *dev, struct ocxl_fn *fn, u8 afu_idx)
>   {
>   	int rc;
>   	struct ocxl_afu *afu;
> @@ -297,41 +271,29 @@ int init_afu(struct pci_dev *dev, struct ocxl_fn *fn, u8 afu_idx)
>   
>   	rc = configure_afu(afu, afu_idx, dev);
>   	if (rc) {
> -		free_afu(afu);
> +		ocxl_afu_put(afu);
>   		return rc;
>   	}
>   
> -	rc = ocxl_register_afu(afu);
> -	if (rc)
> -		goto err;
> -
> -	rc = ocxl_sysfs_add_afu(afu);
> -	if (rc)
> -		goto err;
> -
>   	rc = activate_afu(dev, afu);
> -	if (rc)
> -		goto err_sys;
> +	if (rc) {
> +		deconfigure_afu(afu);
> +		ocxl_afu_put(afu);
> +		return rc;
> +	}
>   
>   	list_add_tail(&afu->list, &fn->afu_list);
> -	return 0;
>   
> -err_sys:
> -	ocxl_sysfs_remove_afu(afu);
> -err:
> -	deconfigure_afu(afu);
> -	device_unregister(&afu->dev);
> -	return rc;
> +	return 0;
>   }
>   
> -void remove_afu(struct ocxl_afu *afu)
> +static void remove_afu(struct ocxl_afu *afu)
>   {
>   	list_del(&afu->list);
>   	ocxl_context_detach_all(afu);
>   	deactivate_afu(afu);
> -	ocxl_sysfs_remove_afu(afu);
>   	deconfigure_afu(afu);
> -	device_unregister(&afu->dev);
> +	ocxl_afu_put(afu); // matches the implicit get in alloc_afu
>   }
>   
>   static struct ocxl_fn *alloc_function(void)
> @@ -358,7 +320,7 @@ static void free_function(struct ocxl_fn *fn)
>   
>   static void free_function_dev(struct device *dev)
>   {
> -	struct ocxl_fn *fn = to_ocxl_function(dev);
> +	struct ocxl_fn *fn = container_of(dev, struct ocxl_fn, dev);
>   
>   	free_function(fn);
>   }
> @@ -372,7 +334,6 @@ static int set_function_device(struct ocxl_fn *fn, struct pci_dev *dev)
>   	rc = dev_set_name(&fn->dev, "ocxlfn.%s", dev_name(&dev->dev));
>   	if (rc)
>   		return rc;
> -	pci_set_drvdata(dev, fn);
>   	return 0;
>   }
>   
> @@ -490,7 +451,7 @@ static void deconfigure_function(struct ocxl_fn *fn)
>   	pci_disable_device(dev);
>   }
>   
> -struct ocxl_fn *init_function(struct pci_dev *dev)
> +static struct ocxl_fn *init_function(struct pci_dev *dev)
>   {
>   	struct ocxl_fn *fn;
>   	int rc;
> @@ -514,8 +475,104 @@ struct ocxl_fn *init_function(struct pci_dev *dev)
>   	return fn;
>   }
>   
> -void remove_function(struct ocxl_fn *fn)
> +// Device detection & initialisation
> +
> +struct ocxl_fn *ocxl_function_open(struct pci_dev *dev)
> +{
> +	int rc, afu_count = 0;
> +	u8 afu;
> +	struct ocxl_fn *fn;
> +
> +	if (!radix_enabled()) {
> +		dev_err(&dev->dev, "Unsupported memory model (hash)\n");
> +		return ERR_PTR(-ENODEV);
> +	}
> +
> +	fn = init_function(dev);
> +	if (IS_ERR(fn)) {
> +		dev_err(&dev->dev, "function init failed: %li\n",
> +			PTR_ERR(fn));
> +		return fn;
> +	}
> +
> +	for (afu = 0; afu <= fn->config.max_afu_index; afu++) {
> +		rc = ocxl_config_check_afu_index(dev, &fn->config, afu);
> +		if (rc > 0) {
> +			rc = init_afu(dev, fn, afu);
> +			if (rc) {
> +				dev_err(&dev->dev,
> +					"Can't initialize AFU index %d\n", afu);
> +				continue;
> +			}
> +			afu_count++;
> +		}
> +	}
> +	dev_info(&dev->dev, "%d AFU(s) configured\n", afu_count);
> +	return fn;
> +}
> +EXPORT_SYMBOL_GPL(ocxl_function_open);
> +
> +struct list_head *ocxl_function_afu_list(struct ocxl_fn *fn)
> +{
> +	return &fn->afu_list;
> +}
> +EXPORT_SYMBOL_GPL(ocxl_function_afu_list);
> +
> +struct ocxl_afu *ocxl_function_fetch_afu(struct ocxl_fn *fn, u8 afu_idx)
> +{
> +	struct ocxl_afu *afu;
> +
> +	list_for_each_entry(afu, &fn->afu_list, list) {
> +		if (afu->config.idx == afu_idx)
> +			return afu;
> +	}
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(ocxl_function_fetch_afu);
> +
> +const struct ocxl_fn_config *ocxl_function_config(struct ocxl_fn *fn)
>   {
> +	return &fn->config;
> +}
> +EXPORT_SYMBOL_GPL(ocxl_function_config);
> +
> +void ocxl_function_close(struct ocxl_fn *fn)
> +{
> +	struct ocxl_afu *afu, *tmp;
> +
> +	list_for_each_entry_safe(afu, tmp, &fn->afu_list, list) {
> +		if (afu->private && afu->private_release)
> +			afu->private_release(afu->private);
> +		remove_afu(afu);
> +	}
> +
>   	deconfigure_function(fn);
>   	device_unregister(&fn->dev);
>   }
> +EXPORT_SYMBOL_GPL(ocxl_function_close);
> +
> +// AFU Metadata
> +
> +struct ocxl_afu_config *ocxl_afu_config(struct ocxl_afu *afu)
> +{
> +	return &afu->config;
> +}
> +EXPORT_SYMBOL_GPL(ocxl_afu_config);
> +
> +void ocxl_afu_set_private(struct ocxl_afu *afu, void *private,
> +			void (*private_release)(void *private))
> +{
> +	afu->private = private;
> +	afu->private_release = private_release;
> +}
> +EXPORT_SYMBOL_GPL(ocxl_afu_set_private);
> +
> +void *ocxl_afu_get_private(struct ocxl_afu *afu)
> +{
> +	if (afu)
> +		return afu->private;
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(ocxl_afu_get_private);
> diff --git a/drivers/misc/ocxl/file.c b/drivers/misc/ocxl/file.c
> index 009e09b7ded5..1f17f8706e29 100644
> --- a/drivers/misc/ocxl/file.c
> +++ b/drivers/misc/ocxl/file.c
> @@ -17,12 +17,10 @@ static struct class *ocxl_class;
>   static struct mutex minors_idr_lock;
>   static struct idr minors_idr;
>   
> -static struct ocxl_afu *find_and_get_afu(dev_t devno)
> +static struct ocxl_file_info *find_file_info(dev_t devno)
>   {
> -	struct ocxl_afu *afu;
> -	int afu_minor;
> +	struct ocxl_file_info *info;
>   
> -	afu_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
> @@ -30,56 +28,52 @@ static struct ocxl_afu *find_and_get_afu(dev_t devno)
>   	 * the device is already at 0, so no user API will access that AFU and
>   	 * this function can't return it.
>   	 */
> -	afu = idr_find(&minors_idr, afu_minor);
> -	if (afu)
> -		ocxl_afu_get(afu);
> -	return afu;
> +	info = idr_find(&minors_idr, MINOR(devno));
> +	return info;
>   }
>   
> -static int allocate_afu_minor(struct ocxl_afu *afu)
> +static int allocate_minor(struct ocxl_file_info *info)
>   {
>   	int minor;
>   
>   	mutex_lock(&minors_idr_lock);
> -	minor = idr_alloc(&minors_idr, afu, 0, OCXL_NUM_MINORS, GFP_KERNEL);
> +	minor = idr_alloc(&minors_idr, info, 0, OCXL_NUM_MINORS, GFP_KERNEL);
>   	mutex_unlock(&minors_idr_lock);
>   	return minor;
>   }
>   
> -static void free_afu_minor(struct ocxl_afu *afu)
> +static void free_minor(struct ocxl_file_info *info)
>   {
>   	mutex_lock(&minors_idr_lock);
> -	idr_remove(&minors_idr, MINOR(afu->dev.devt));
> +	idr_remove(&minors_idr, MINOR(info->dev.devt));
>   	mutex_unlock(&minors_idr_lock);
>   }
>   
>   static int afu_open(struct inode *inode, struct file *file)
>   {
> -	struct ocxl_afu *afu;
> +	struct ocxl_file_info *info;
>   	struct ocxl_context *ctx;
>   	int rc;
>   
>   	pr_debug("%s for device %x\n", __func__, inode->i_rdev);
>   
> -	afu = find_and_get_afu(inode->i_rdev);
> -	if (!afu)
> +	info = find_file_info(inode->i_rdev);
> +	if (!info)
>   		return -ENODEV;
>   
>   	ctx = ocxl_context_alloc();
>   	if (!ctx) {
>   		rc = -ENOMEM;
> -		goto put_afu;
> +		goto err;
>   	}
>   
> -	rc = ocxl_context_init(ctx, afu, inode->i_mapping);
> +	rc = ocxl_context_init(ctx, info->afu, inode->i_mapping);
>   	if (rc)
> -		goto put_afu;
> +		goto err;
>   	file->private_data = ctx;
> -	ocxl_afu_put(afu);
>   	return 0;
>   
> -put_afu:
> -	ocxl_afu_put(afu);
> +err:
>   	return rc;
>   }
>   
> @@ -204,11 +198,16 @@ static long afu_ioctl(struct file *file, unsigned int cmd,
>   	struct ocxl_ioctl_irq_fd irq_fd;
>   	u64 irq_offset;
>   	long rc;
> +	bool closed;
>   
>   	pr_debug("%s for context %d, command %s\n", __func__, ctx->pasid,
>   		CMD_STR(cmd));
>   
> -	if (ctx->status == CLOSED)
> +	mutex_lock(&ctx->status_mutex);
> +	closed = (ctx->status == CLOSED);
> +	mutex_unlock(&ctx->status_mutex);
> +
> +	if (closed)
>   		return -EIO;
>   
>   	switch (cmd) {
> @@ -468,39 +467,83 @@ static const struct file_operations ocxl_afu_fops = {
>   	.release        = afu_release,
>   };
>   
> -int ocxl_create_cdev(struct ocxl_afu *afu)
> +// Called when there are no more consumers of the AFU
> +static void ocxl_file_release(void *private)
>   {
> -	int rc;
> +	struct ocxl_file_info *info = private;
>   
> -	cdev_init(&afu->cdev, &ocxl_afu_fops);
> -	rc = cdev_add(&afu->cdev, afu->dev.devt, 1);
> -	if (rc) {
> -		dev_err(&afu->dev, "Unable to add afu char device: %d\n", rc);
> -		return rc;
> -	}
> -	return 0;
> +	ocxl_sysfs_unregister_afu(info->afu);
> +	device_unregister(&info->dev);
> +
> +	free_minor(info);
>   }
>   
> -void ocxl_destroy_cdev(struct ocxl_afu *afu)
> +// Free the info struct
> +static void info_release(struct device *dev)
>   {
> -	cdev_del(&afu->cdev);
> +	struct ocxl_file_info *info = container_of(dev, struct ocxl_file_info, dev);
> +	kfree(info);
>   }
>   
> -int ocxl_register_afu(struct ocxl_afu *afu)
> +int ocxl_file_register_afu(struct ocxl_afu *afu)
>   {
>   	int minor;
> +	int rc;
> +	struct ocxl_file_info *info;
> +	struct ocxl_fn *fn = afu->fn;
> +	struct pci_dev *pci_dev = to_pci_dev(fn->dev.parent);
> +
> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> +	if (info == NULL)
> +		return -ENOMEM;
> +
> +	info->afu = afu;
>   
> -	minor = allocate_afu_minor(afu);
> -	if (minor < 0)
> +	minor = allocate_minor(info);
> +	if (minor < 0) {
> +		kfree(info);
>   		return minor;
> -	afu->dev.devt = MKDEV(MAJOR(ocxl_dev), minor);
> -	afu->dev.class = ocxl_class;
> -	return device_register(&afu->dev);
> +	}
> +
> +	info->dev.parent = &fn->dev;
> +	info->dev.devt = MKDEV(MAJOR(ocxl_dev), minor);
> +	info->dev.class = ocxl_class;
> +	info->dev.release = info_release;
> +
> +	ocxl_afu_set_private(afu, info, ocxl_file_release);
> +
> +	rc = dev_set_name(&info->dev, "%s.%s.%hhu",
> +		afu->config.name, dev_name(&pci_dev->dev), afu->config.idx);
> +	if (rc)
> +		return rc;
> +
> +	rc = device_register(&info->dev);
> +	if (rc)
> +		return rc;
> +
> +	return ocxl_sysfs_register_afu(afu);
>   }
>   
> -void ocxl_unregister_afu(struct ocxl_afu *afu)
> +int ocxl_file_make_visible(struct ocxl_afu *afu)
>   {
> -	free_afu_minor(afu);
> +	int rc;
> +	struct ocxl_file_info *info = ocxl_afu_get_private(afu);
> +
> +	cdev_init(&info->cdev, &ocxl_afu_fops);
> +	rc = cdev_add(&info->cdev, info->dev.devt, 1);
> +	if (rc) {
> +		dev_err(&info->dev, "Unable to add afu char device: %d\n", rc);
> +		return rc;
> +	}
> +
> +	return 0;
> +}
> +
> +void ocxl_file_make_invisible(struct ocxl_afu *afu)
> +{
> +	struct ocxl_file_info *info = ocxl_afu_get_private(afu);
> +
> +	cdev_del(&info->cdev);
>   }
>   
>   static char *ocxl_devnode(struct device *dev, umode_t *mode)
> diff --git a/drivers/misc/ocxl/ocxl_internal.h b/drivers/misc/ocxl/ocxl_internal.h
> index 81086534dab5..05930a29f606 100644
> --- a/drivers/misc/ocxl/ocxl_internal.h
> +++ b/drivers/misc/ocxl/ocxl_internal.h
> @@ -11,9 +11,6 @@
>   #define MAX_IRQ_PER_LINK	2000
>   #define MAX_IRQ_PER_CONTEXT	MAX_IRQ_PER_LINK
>   
> -#define to_ocxl_function(d) container_of(d, struct ocxl_fn, dev)
> -#define to_ocxl_afu(d) container_of(d, struct ocxl_afu, dev)
> -
>   extern struct pci_driver ocxl_pci_driver;
>   
>   struct ocxl_fn {
> @@ -30,11 +27,17 @@ struct ocxl_fn {
>   	void *link;
>   };
>   
> +struct ocxl_file_info {
> +	struct ocxl_afu *afu;
> +	struct device dev;
> +	struct cdev cdev;
> +	struct bin_attribute attr_global_mmio;
> +};
> +
>   struct ocxl_afu {
> +	struct kref kref;
>   	struct ocxl_fn *fn;
>   	struct list_head list;
> -	struct device dev;
> -	struct cdev cdev;
>   	struct ocxl_afu_config config;
>   	int pasid_base;
>   	int pasid_count; /* opened contexts */
> @@ -48,7 +51,9 @@ struct ocxl_afu {
>   	u64 irq_base_offset;
>   	void __iomem *global_mmio_ptr;
>   	u64 pp_mmio_start;
> -	struct bin_attribute attr_global_mmio;
> +	void *private;
> +	void (*private_release)(void *private);
> +
>   };
>   
>   enum ocxl_context_status {
> @@ -91,13 +96,11 @@ struct ocxl_process_element {
>   	__be32 software_state;
>   };
>   
> -struct ocxl_afu *ocxl_afu_get(struct ocxl_afu *afu);
> -void ocxl_afu_put(struct ocxl_afu *afu);
> -
>   int ocxl_create_cdev(struct ocxl_afu *afu);
>   void ocxl_destroy_cdev(struct ocxl_afu *afu);
> -int ocxl_register_afu(struct ocxl_afu *afu);
> -void ocxl_unregister_afu(struct ocxl_afu *afu);
> +int ocxl_file_register_afu(struct ocxl_afu *afu);
> +int ocxl_file_make_visible(struct ocxl_afu *afu);
> +void ocxl_file_make_invisible(struct ocxl_afu *afu);
>   
>   int ocxl_file_init(void);
>   void ocxl_file_exit(void);
> @@ -140,8 +143,8 @@ int ocxl_context_detach(struct ocxl_context *ctx);
>   void ocxl_context_detach_all(struct ocxl_afu *afu);
>   void ocxl_context_free(struct ocxl_context *ctx);
>   
> -int ocxl_sysfs_add_afu(struct ocxl_afu *afu);
> -void ocxl_sysfs_remove_afu(struct ocxl_afu *afu);
> +int ocxl_sysfs_register_afu(struct ocxl_afu *afu);
> +void ocxl_sysfs_unregister_afu(struct ocxl_afu *afu);
>   
>   int ocxl_afu_irq_alloc(struct ocxl_context *ctx, u64 *irq_offset);
>   int ocxl_afu_irq_free(struct ocxl_context *ctx, u64 irq_offset);
> @@ -150,9 +153,11 @@ int ocxl_afu_irq_set_fd(struct ocxl_context *ctx, u64 irq_offset,
>   			int eventfd);
>   u64 ocxl_afu_irq_get_addr(struct ocxl_context *ctx, u64 irq_offset);
>   
> -struct ocxl_fn *init_function(struct pci_dev *dev);
> -void remove_function(struct ocxl_fn *fn);
> -int init_afu(struct pci_dev *dev, struct ocxl_fn *fn, u8 afu_idx);
> -void remove_afu(struct ocxl_afu *afu);
> +/**
> + * Free an AFU
> + *
> + * afu: The AFU to free
> + */
> +void ocxl_free_afu(struct ocxl_afu *afu);
>   
>   #endif /* _OCXL_INTERNAL_H_ */
> diff --git a/drivers/misc/ocxl/pci.c b/drivers/misc/ocxl/pci.c
> index 5926c863716c..a1ed2bb02e4b 100644
> --- a/drivers/misc/ocxl/pci.c
> +++ b/drivers/misc/ocxl/pci.c
> @@ -16,47 +16,48 @@ MODULE_DEVICE_TABLE(pci, ocxl_pci_tbl);
>   
>   static int ocxl_probe(struct pci_dev *dev, const struct pci_device_id *id)
>   {
> -	int rc, afu_count = 0;
> -	u8 afu;
> +	int rc;
> +	struct ocxl_afu *afu, *tmp;
>   	struct ocxl_fn *fn;
> +	struct list_head *afu_list;
>   
> -	if (!radix_enabled()) {
> -		dev_err(&dev->dev, "Unsupported memory model (hash)\n");
> -		return -ENODEV;
> -	}
> -
> -	fn = init_function(dev);
> -	if (IS_ERR(fn)) {
> -		dev_err(&dev->dev, "function init failed: %li\n",
> -			PTR_ERR(fn));
> +	fn = ocxl_function_open(dev);
> +	if (IS_ERR(fn))
>   		return PTR_ERR(fn);
> -	}
>   
> -	for (afu = 0; afu <= fn->config.max_afu_index; afu++) {
> -		rc = ocxl_config_check_afu_index(dev, &fn->config, afu);
> -		if (rc > 0) {
> -			rc = init_afu(dev, fn, afu);
> -			if (rc) {
> -				dev_err(&dev->dev,
> -					"Can't initialize AFU index %d\n", afu);
> -				continue;
> -			}
> -			afu_count++;
> -		}
> +	pci_set_drvdata(dev, fn);
> +
> +	afu_list = ocxl_function_afu_list(fn);
> +
> +	list_for_each_entry_safe(afu, tmp, afu_list, list) {
> +		rc = ocxl_file_register_afu(afu);
> +		if (rc)
> +			continue;
> +
> +		rc = ocxl_file_make_visible(afu);
> +		if (rc)
> +			continue;
> +
> +		// Defer error cleanup until the device is removed
>   	}
> -	dev_info(&dev->dev, "%d AFU(s) configured\n", afu_count);
> +
>   	return 0;
>   }
>   
> -static void ocxl_remove(struct pci_dev *dev)
> +void ocxl_remove(struct pci_dev *dev)
>   {
> -	struct ocxl_afu *afu, *tmp;
> -	struct ocxl_fn *fn = pci_get_drvdata(dev);
> +	struct ocxl_fn *fn;
> +	struct ocxl_afu *afu;
> +	struct list_head *afu_list;
> +
> +	fn = pci_get_drvdata(dev);
> +	afu_list = ocxl_function_afu_list(fn);
>   
> -	list_for_each_entry_safe(afu, tmp, &fn->afu_list, list) {
> -		remove_afu(afu);
> +	list_for_each_entry(afu, afu_list, list) {
> +		ocxl_file_make_invisible(afu);
>   	}
> -	remove_function(fn);
> +
> +	ocxl_function_close(fn);
>   }
>   
>   struct pci_driver ocxl_pci_driver = {
> diff --git a/drivers/misc/ocxl/sysfs.c b/drivers/misc/ocxl/sysfs.c
> index 0ab1fd1b2682..a67931f1feec 100644
> --- a/drivers/misc/ocxl/sysfs.c
> +++ b/drivers/misc/ocxl/sysfs.c
> @@ -3,11 +3,18 @@
>   #include <linux/sysfs.h>
>   #include "ocxl_internal.h"
>   
> +static inline struct ocxl_afu *to_afu(struct device *device)
> +{
> +	struct ocxl_file_info *info = container_of(device, struct ocxl_file_info, dev);
> +
> +	return info->afu;
> +}
> +
>   static ssize_t global_mmio_size_show(struct device *device,
>   				struct device_attribute *attr,
>   				char *buf)
>   {
> -	struct ocxl_afu *afu = to_ocxl_afu(device);
> +	struct ocxl_afu *afu = to_afu(device);
>   
>   	return scnprintf(buf, PAGE_SIZE, "%d\n",
>   			afu->config.global_mmio_size);
> @@ -17,7 +24,7 @@ static ssize_t pp_mmio_size_show(struct device *device,
>   				struct device_attribute *attr,
>   				char *buf)
>   {
> -	struct ocxl_afu *afu = to_ocxl_afu(device);
> +	struct ocxl_afu *afu = to_afu(device);
>   
>   	return scnprintf(buf, PAGE_SIZE, "%d\n",
>   			afu->config.pp_mmio_stride);
> @@ -27,7 +34,7 @@ static ssize_t afu_version_show(struct device *device,
>   				struct device_attribute *attr,
>   				char *buf)
>   {
> -	struct ocxl_afu *afu = to_ocxl_afu(device);
> +	struct ocxl_afu *afu = to_afu(device);
>   
>   	return scnprintf(buf, PAGE_SIZE, "%hhu:%hhu\n",
>   			afu->config.version_major,
> @@ -38,7 +45,7 @@ static ssize_t contexts_show(struct device *device,
>   		struct device_attribute *attr,
>   		char *buf)
>   {
> -	struct ocxl_afu *afu = to_ocxl_afu(device);
> +	struct ocxl_afu *afu = to_afu(device);
>   
>   	return scnprintf(buf, PAGE_SIZE, "%d/%d\n",
>   			afu->pasid_count, afu->pasid_max);
> @@ -55,7 +62,7 @@ static ssize_t global_mmio_read(struct file *filp, struct kobject *kobj,
>   				struct bin_attribute *bin_attr, char *buf,
>   				loff_t off, size_t count)
>   {
> -	struct ocxl_afu *afu = to_ocxl_afu(kobj_to_dev(kobj));
> +	struct ocxl_afu *afu = to_afu(kobj_to_dev(kobj));
>   
>   	if (count == 0 || off < 0 ||
>   		off >= afu->config.global_mmio_size)
> @@ -86,7 +93,7 @@ static int global_mmio_mmap(struct file *filp, struct kobject *kobj,
>   			struct bin_attribute *bin_attr,
>   			struct vm_area_struct *vma)
>   {
> -	struct ocxl_afu *afu = to_ocxl_afu(kobj_to_dev(kobj));
> +	struct ocxl_afu *afu = to_afu(kobj_to_dev(kobj));
>   
>   	if ((vma_pages(vma) + vma->vm_pgoff) >
>   		(afu->config.global_mmio_size >> PAGE_SHIFT))
> @@ -99,27 +106,29 @@ static int global_mmio_mmap(struct file *filp, struct kobject *kobj,
>   	return 0;
>   }
>   
> -int ocxl_sysfs_add_afu(struct ocxl_afu *afu)
> +int ocxl_sysfs_register_afu(struct ocxl_afu *afu)
>   {
>   	int i, rc;
> +	struct ocxl_file_info *info = ocxl_afu_get_private(afu);
> +
> +	if (!info)
> +		return -EFAULT; // ocxl_file_register_afu() must be called first
>   
>   	for (i = 0; i < ARRAY_SIZE(afu_attrs); i++) {
> -		rc = device_create_file(&afu->dev, &afu_attrs[i]);
> +		rc = device_create_file(&info->dev, &afu_attrs[i]);
>   		if (rc)
>   			goto err;
>   	}
>   
> -	sysfs_attr_init(&afu->attr_global_mmio.attr);
> -	afu->attr_global_mmio.attr.name = "global_mmio_area";
> -	afu->attr_global_mmio.attr.mode = 0600;
> -	afu->attr_global_mmio.size = afu->config.global_mmio_size;
> -	afu->attr_global_mmio.read = global_mmio_read;
> -	afu->attr_global_mmio.mmap = global_mmio_mmap;
> -	rc = device_create_bin_file(&afu->dev, &afu->attr_global_mmio);
> +	sysfs_attr_init(&info->attr_global_mmio.attr);
> +	info->attr_global_mmio.attr.name = "global_mmio_area";
> +	info->attr_global_mmio.attr.mode = 0600;
> +	info->attr_global_mmio.size = afu->config.global_mmio_size;
> +	info->attr_global_mmio.read = global_mmio_read;
> +	info->attr_global_mmio.mmap = global_mmio_mmap;
> +	rc = device_create_bin_file(&info->dev, &info->attr_global_mmio);
>   	if (rc) {
> -		dev_err(&afu->dev,
> -			"Unable to create global mmio attr for afu: %d\n",
> -			rc);
> +		dev_err(&info->dev, "Unable to create global mmio attr for afu: %d\n", rc);
>   		goto err;
>   	}
>   
> @@ -127,15 +136,20 @@ int ocxl_sysfs_add_afu(struct ocxl_afu *afu)
>   
>   err:
>   	for (i--; i >= 0; i--)
> -		device_remove_file(&afu->dev, &afu_attrs[i]);
> +		device_remove_file(&info->dev, &afu_attrs[i]);
> +
>   	return rc;
>   }
>   
> -void ocxl_sysfs_remove_afu(struct ocxl_afu *afu)
> +void ocxl_sysfs_unregister_afu(struct ocxl_afu *afu)
>   {
> +	struct ocxl_file_info *info = ocxl_afu_get_private(afu);
>   	int i;
>   
> +	if (!info)
> +		return;
> +
>   	for (i = 0; i < ARRAY_SIZE(afu_attrs); i++)
> -		device_remove_file(&afu->dev, &afu_attrs[i]);
> -	device_remove_bin_file(&afu->dev, &afu->attr_global_mmio);
> +		device_remove_file(&info->dev, &afu_attrs[i]);
> +	device_remove_bin_file(&info->dev, &info->attr_global_mmio);
>   }
> diff --git a/include/misc/ocxl.h b/include/misc/ocxl.h
> index 9530d3be1b30..7d611ea68a59 100644
> --- a/include/misc/ocxl.h
> +++ b/include/misc/ocxl.h
> @@ -16,11 +16,7 @@
>   
>   #define OCXL_AFU_NAME_SZ      (24+1)  /* add 1 for NULL termination */
>   
> -/*
> - * The following 2 structures are a fairly generic way of representing
> - * the configuration data for a function and AFU, as read from the
> - * configuration space.
> - */
> +
>   struct ocxl_afu_config {
>   	u8 idx;
>   	int dvsec_afu_control_pos; /* offset of AFU control DVSEC */
> @@ -49,12 +45,110 @@ struct ocxl_fn_config {
>   	s8 max_afu_index;
>   };
>   
> -/*
> - * Read the configuration space of a function and fill in a
> - * ocxl_fn_config structure with all the function details
> +// These are opaque outside the ocxl driver
> +struct ocxl_afu;
> +struct ocxl_fn;
> +
> +// Device detection & initialisation
> +
> +/**
> + * Open an OpenCAPI function on an OpenCAPI device
> + *
> + * @dev: The PCI device that contains the function
> + *
> + * Returns an opaque pointer to the function, or an error pointer (check with IS_ERR)
>    */
> -int ocxl_config_read_function(struct pci_dev *dev,
> -				struct ocxl_fn_config *fn);
> +struct ocxl_fn *ocxl_function_open(struct pci_dev *dev);
> +
> +/**
> + * Get the list of AFUs associated with a PCI function device
> + *
> + * Returns a list of struct ocxl_afu *
> + *
> + * @fn: The OpenCAPI function containing the AFUs
> + */
> +struct list_head *ocxl_function_afu_list(struct ocxl_fn *fn);
> +
> +/**
> + * Fetch an AFU instance from an OpenCAPI function
> + *
> + * @fn: The OpenCAPI function to get the AFU from
> + * @afu_idx: The index of the AFU to get
> + *
> + * If successful, the AFU should be released with ocxl_afu_put()
> + *
> + * Returns a pointer to the AFU, or NULL on error
> + */
> +struct ocxl_afu *ocxl_function_fetch_afu(struct ocxl_fn *fn, u8 afu_idx);
> +
> +/**
> + * Take a reference to an AFU
> + *
> + * @afu: The AFU to increment the reference count on
> + */
> +void ocxl_afu_get(struct ocxl_afu *afu);
> +
> +/**
> + * Release a reference to an AFU
> + *
> + * @afu: The AFU to decrement the reference count on
> + */
> +void ocxl_afu_put(struct ocxl_afu *afu);
> +
> +
> +/**
> + * Get the configuration information for an OpenCAPI function
> + *
> + * @fn: The OpenCAPI function to get the config for
> + *
> + * Returns the function config, or NULL on error
> + */
> +const struct ocxl_fn_config *ocxl_function_config(struct ocxl_fn *fn);
> +
> +/**
> + * Close an OpenCAPI function
> + *
> + * This will free any AFUs previously retrieved from the function, and
> + * detach and associated contexts. The contexts must by freed by the caller.
> + *
> + * @fn: The OpenCAPI function to close
> + *
> + */
> +void ocxl_function_close(struct ocxl_fn *fn);
> +
> +// AFU Metadata
> +
> +/**
> + * Get a pointer to the config for an AFU
> + *
> + * @afu: a pointer to the AFU to get the config for
> + *
> + * Returns a pointer to the AFU config
> + */
> +struct ocxl_afu_config *ocxl_afu_config(struct ocxl_afu *afu);
> +
> +/**
> + * Assign opaque hardware specific information to an OpenCAPI AFU.
> + *
> + * @dev: The PCI device associated with the OpenCAPI device
> + * @private: the opaque hardware specific information to assign to the driver
> + * @private_release: A callback to free the private data
> + */
> +void ocxl_afu_set_private(struct ocxl_afu *afu, void *private,
> +			void (*private_release)(void *private));
> +
> +/**
> + * Fetch the hardware specific information associated with an external OpenCAPI
> + * AFU. This may be consumed by an external OpenCAPI driver.
> + *
> + * @afu: The AFU
> + *
> + * Returns the opaque pointer associated with the device, or NULL if not set
> + */
> +void *ocxl_afu_get_private(struct ocxl_afu *dev);
> +
> +
> +// Functions left here are for compatibility with the cxlflash driver
>   
>   /*
>    * Read the configuration space of a function for the AFU specified by
> @@ -141,6 +235,13 @@ int ocxl_config_set_TL(struct pci_dev *dev, int tl_dvsec);
>   int ocxl_config_terminate_pasid(struct pci_dev *dev,
>   				int afu_control_offset, int pasid);
>   
> +/*
> + * Read the configuration space of a function and fill in a
> + * ocxl_fn_config structure with all the function details
> + */
> +int ocxl_config_read_function(struct pci_dev *dev,
> +				struct ocxl_fn_config *fn);
> +
>   /*
>    * Set up the opencapi link for the function.
>    *
> 

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