char: xillybus: Move class-related functions to new xillybus_class.c

This patch is a preparation for adding another related driver, XillyUSB.
In order to share some code between the existing Xillybus driver and the
one to be added, some functions are moved to xillybus_class.c

XILLYBUS_CLASS is added to Kconfig and is common to all drivers in this
group. The relation with the existing XILLYBUS symbol is "select" rather
than "depends on" XILLYBUS_CLASS, or else "make olddefconfig" will silently
turn off XILLYBUS, which is currently enabled in several distributions.

XILLYBUS_CLASS doesn't depend on anything else, hence using it with
"select" poses no risk for a broken configuration.

After the future addition of the XillyUSB module, the tree of symbols
will be as follows:

XILLYBUS_CLASS --+-- XILLYBUS --+-- XILLYBUS_PCIE
| |
| +-- XILLYBUS_OF
|
+-- XILLYUSB

XILLYBUS is for drivers based upon memory registers + DMA-based interfaces,
and it's combined with XILLYBUS_PCIE and/or XILLYBUS_OF.

XILLYUSB is for the USB variant only.

Or a more detailed, bottom-up outline:

* CONFIG_XILLYBUS_PCIE -> xillybus_pcie.c: Functions related to PCIe.
* CONFIG_XILLYBUS_OF -> xillybus_of.c: Functions related to Xillybus as a
peripheral on an FPGA / Processor combo chip.
* CONFIG_XILLYBUS -> xillybus_core.c: Functions that are common to the two
above, mainly access to the peripheral with memory-mapped registers and
DMA.
* CONFIG_XILLYUSB -> xillyusb.c: The driver for the USB variant, accesses
the peripheral through the USB framework.
* CONFIG_XILLYBUS_CLASS -> xillybus_class.c: The new module, which contains
the class and API parts that would otherwise appear both in
xillybus_core.c and xillyusb.c. Contains utility functions for the two
latter.

And since I'm at it, comments on the module names are added in the
Kconfig's help part.

The functions are exported with the non-GPL EXPORT_SYMBOL (a matter of
taste).

Signed-off-by: Eli Billauer <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/char/xillybus/Kconfig

···
 # Xillybus devices
 #
 
+config XILLYBUS_CLASS
+	tristate
+
 config XILLYBUS
 	tristate "Xillybus generic FPGA interface"
 	depends on PCI || OF
 	select CRC32
+	select XILLYBUS_CLASS
 	help
 	  Xillybus is a generic interface for peripherals designed on
 	  programmable logic (FPGA). The driver probes the hardware for
···
 	depends on PCI_MSI
 	help
 	  Set to M if you want Xillybus to use PCI Express for communicating
-	  with the FPGA.
+	  with the FPGA. The module will be called xillybus_pcie.
 
 config XILLYBUS_OF
 	tristate "Xillybus over Device Tree"
···
 	help
 	  Set to M if you want Xillybus to find its resources from the
 	  Open Firmware Flattened Device Tree. If the target is an embedded
-	  system, say M.
+	  system, say M. The module will be called xillybus_of.
 
 endif # if XILLYBUS

drivers/char/xillybus/Makefile

···
 # Makefile for Xillybus driver
 #
 
+obj-$(CONFIG_XILLYBUS_CLASS)	+= xillybus_class.o
 obj-$(CONFIG_XILLYBUS)		+= xillybus_core.o
 obj-$(CONFIG_XILLYBUS_PCIE)	+= xillybus_pcie.o
 obj-$(CONFIG_XILLYBUS_OF)	+= xillybus_of.o

drivers/char/xillybus/xillybus.h

···
 
 struct xilly_idt_handle {
 	unsigned char *chandesc;
-	unsigned char *idt;
+	unsigned char *names;
+	int names_len;
 	int entries;
 };
 
···
 	struct device *dev;
 	struct xilly_endpoint_hardware *ephw;
 
-	struct list_head ep_list;
 	int dma_using_dac; /* =1 if 64-bit DMA is used, =0 otherwise. */
 	__iomem void *registers;
 	int fatal_error;
 
 	struct mutex register_mutex;
 	wait_queue_head_t ep_wait;
-
-	/* Channels and message handling */
-	struct cdev cdev;
-
-	int major;
-	int lowest_minor; /* Highest minor = lowest_minor + num_channels - 1 */
 
 	int num_channels; /* EXCLUDING message buffer */
 	struct xilly_channel **channels;

drivers/char/xillybus/xillybus_class.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2021 Xillybus Ltd, http://xillybus.com
+ *
+ * Driver for the Xillybus class
+ */
+
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/cdev.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+
+#include "xillybus_class.h"
+
+MODULE_DESCRIPTION("Driver for Xillybus class");
+MODULE_AUTHOR("Eli Billauer, Xillybus Ltd.");
+MODULE_VERSION("1.0");
+MODULE_ALIAS("xillybus_class");
+MODULE_LICENSE("GPL v2");
+
+static DEFINE_MUTEX(unit_mutex);
+static LIST_HEAD(unit_list);
+static struct class *xillybus_class;
+
+#define UNITNAMELEN 16
+
+struct xilly_unit {
+	struct list_head list_entry;
+	void *private_data;
+
+	struct cdev *cdev;
+	char name[UNITNAMELEN];
+	int major;
+	int lowest_minor;
+	int num_nodes;
+};
+
+int xillybus_init_chrdev(struct device *dev,
+			 const struct file_operations *fops,
+			 struct module *owner,
+			 void *private_data,
+			 unsigned char *idt, unsigned int len,
+			 int num_nodes,
+			 const char *prefix, bool enumerate)
+{
+	int rc;
+	dev_t mdev;
+	int i;
+	char devname[48];
+
+	struct device *device;
+	size_t namelen;
+	struct xilly_unit *unit, *u;
+
+	unit = kzalloc(sizeof(*unit), GFP_KERNEL);
+
+	if (!unit)
+		return -ENOMEM;
+
+	mutex_lock(&unit_mutex);
+
+	if (!enumerate)
+		snprintf(unit->name, UNITNAMELEN, "%s", prefix);
+
+	for (i = 0; enumerate; i++) {
+		snprintf(unit->name, UNITNAMELEN, "%s_%02d",
+			 prefix, i);
+
+		enumerate = false;
+		list_for_each_entry(u, &unit_list, list_entry)
+			if (!strcmp(unit->name, u->name)) {
+				enumerate = true;
+				break;
+			}
+	}
+
+	rc = alloc_chrdev_region(&mdev, 0, num_nodes, unit->name);
+
+	if (rc) {
+		dev_warn(dev, "Failed to obtain major/minors");
+		goto fail_obtain;
+	}
+
+	unit->major = MAJOR(mdev);
+	unit->lowest_minor = MINOR(mdev);
+	unit->num_nodes = num_nodes;
+	unit->private_data = private_data;
+
+	unit->cdev = cdev_alloc();
+	if (!unit->cdev) {
+		rc = -ENOMEM;
+		goto unregister_chrdev;
+	}
+	unit->cdev->ops = fops;
+	unit->cdev->owner = owner;
+
+	rc = cdev_add(unit->cdev, MKDEV(unit->major, unit->lowest_minor),
+		      unit->num_nodes);
+	if (rc) {
+		dev_err(dev, "Failed to add cdev.\n");
+		/* kobject_put() is normally done by cdev_del() */
+		kobject_put(&unit->cdev->kobj);
+		goto unregister_chrdev;
+	}
+
+	for (i = 0; i < num_nodes; i++) {
+		namelen = strnlen(idt, len);
+
+		if (namelen == len) {
+			dev_err(dev, "IDT's list of names is too short. This is exceptionally weird, because its CRC is OK\n");
+			rc = -ENODEV;
+			goto unroll_device_create;
+		}
+
+		snprintf(devname, sizeof(devname), "%s_%s",
+			 unit->name, idt);
+
+		len -= namelen + 1;
+		idt += namelen + 1;
+
+		device = device_create(xillybus_class,
+				       NULL,
+				       MKDEV(unit->major,
+					     i + unit->lowest_minor),
+				       NULL,
+				       "%s", devname);
+
+		if (IS_ERR(device)) {
+			dev_err(dev, "Failed to create %s device. Aborting.\n",
+				devname);
+			rc = -ENODEV;
+			goto unroll_device_create;
+		}
+	}
+
+	if (len) {
+		dev_err(dev, "IDT's list of names is too long. This is exceptionally weird, because its CRC is OK\n");
+		rc = -ENODEV;
+		goto unroll_device_create;
+	}
+
+	list_add_tail(&unit->list_entry, &unit_list);
+
+	dev_info(dev, "Created %d device files.\n", num_nodes);
+
+	mutex_unlock(&unit_mutex);
+
+	return 0;
+
+unroll_device_create:
+	for (i--; i >= 0; i--)
+		device_destroy(xillybus_class, MKDEV(unit->major,
+						     i + unit->lowest_minor));
+
+	cdev_del(unit->cdev);
+
+unregister_chrdev:
+	unregister_chrdev_region(MKDEV(unit->major, unit->lowest_minor),
+				 unit->num_nodes);
+
+fail_obtain:
+	mutex_unlock(&unit_mutex);
+
+	kfree(unit);
+
+	return rc;
+}
+EXPORT_SYMBOL(xillybus_init_chrdev);
+
+void xillybus_cleanup_chrdev(void *private_data,
+			     struct device *dev)
+{
+	int minor;
+	struct xilly_unit *unit;
+	bool found = false;
+
+	mutex_lock(&unit_mutex);
+
+	list_for_each_entry(unit, &unit_list, list_entry)
+		if (unit->private_data == private_data) {
+			found = true;
+			break;
+		}
+
+	if (!found) {
+		dev_err(dev, "Weird bug: Failed to find unit\n");
+		mutex_unlock(&unit_mutex);
+		return;
+	}
+
+	for (minor = unit->lowest_minor;
+	     minor < (unit->lowest_minor + unit->num_nodes);
+	     minor++)
+		device_destroy(xillybus_class, MKDEV(unit->major, minor));
+
+	cdev_del(unit->cdev);
+
+	unregister_chrdev_region(MKDEV(unit->major, unit->lowest_minor),
+				 unit->num_nodes);
+
+	dev_info(dev, "Removed %d device files.\n",
+		 unit->num_nodes);
+
+	list_del(&unit->list_entry);
+	kfree(unit);
+
+	mutex_unlock(&unit_mutex);
+}
+EXPORT_SYMBOL(xillybus_cleanup_chrdev);
+
+int xillybus_find_inode(struct inode *inode,
+			void **private_data, int *index)
+{
+	int minor = iminor(inode);
+	int major = imajor(inode);
+	struct xilly_unit *unit;
+	bool found = false;
+
+	mutex_lock(&unit_mutex);
+
+	list_for_each_entry(unit, &unit_list, list_entry)
+		if (unit->major == major &&
+		    minor >= unit->lowest_minor &&
+		    minor < (unit->lowest_minor + unit->num_nodes)) {
+			found = true;
+			break;
+		}
+
+	mutex_unlock(&unit_mutex);
+
+	if (!found)
+		return -ENODEV;
+
+	*private_data = unit->private_data;
+	*index = minor - unit->lowest_minor;
+
+	return 0;
+}
+EXPORT_SYMBOL(xillybus_find_inode);
+
+static int __init xillybus_class_init(void)
+{
+	xillybus_class = class_create(THIS_MODULE, "xillybus");
+
+	if (IS_ERR(xillybus_class)) {
+		pr_warn("Failed to register xillybus class\n");
+
+		return PTR_ERR(xillybus_class);
+	}
+	return 0;
+}
+
+static void __exit xillybus_class_exit(void)
+{
+	class_destroy(xillybus_class);
+}
+
+module_init(xillybus_class_init);
+module_exit(xillybus_class_exit);

drivers/char/xillybus/xillybus_class.h

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2021 Xillybus Ltd, http://www.xillybus.com
+ *
+ * Header file for the Xillybus class
+ */
+
+#ifndef __XILLYBUS_CLASS_H
+#define __XILLYBUS_CLASS_H
+
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+
+int xillybus_init_chrdev(struct device *dev,
+			 const struct file_operations *fops,
+			 struct module *owner,
+			 void *private_data,
+			 unsigned char *idt, unsigned int len,
+			 int num_nodes,
+			 const char *prefix, bool enumerate);
+
+void xillybus_cleanup_chrdev(void *private_data,
+			     struct device *dev);
+
+int xillybus_find_inode(struct inode *inode,
+			void **private_data, int *index);
+
+#endif /* __XILLYBUS_CLASS_H */

drivers/char/xillybus/xillybus_core.c

···
 #include <linux/interrupt.h>
 #include <linux/sched.h>
 #include <linux/fs.h>
-#include <linux/cdev.h>
 #include <linux/spinlock.h>
 #include <linux/mutex.h>
 #include <linux/crc32.h>
···
 #include <linux/slab.h>
 #include <linux/workqueue.h>
 #include "xillybus.h"
+#include "xillybus_class.h"
 
 MODULE_DESCRIPTION("Xillybus core functions");
 MODULE_AUTHOR("Eli Billauer, Xillybus Ltd.");
-MODULE_VERSION("1.07");
+MODULE_VERSION("1.10");
 MODULE_ALIAS("xillybus_core");
 MODULE_LICENSE("GPL v2");
 
···
 
 static const char xillyname[] = "xillybus";
 
-static struct class *xillybus_class;
-
-/*
- * ep_list_lock is the last lock to be taken; No other lock requests are
- * allowed while holding it. It merely protects list_of_endpoints, and not
- * the endpoints listed in it.
- */
-
-static LIST_HEAD(list_of_endpoints);
-static struct mutex ep_list_lock;
 static struct workqueue_struct *xillybus_wq;
 
 /*
···
 	unsigned char *scan;
 	int len;
 
-	scan = idt;
-	idt_handle->idt = idt;
-
-	scan++; /* Skip version number */
+	scan = idt + 1;
+	idt_handle->names = scan;
 
 	while ((scan <= end_of_idt) && *scan) {
 		while ((scan <= end_of_idt) && *scan++)
 			/* Do nothing, just scan thru string */;
 		count++;
 	}
+
+	idt_handle->names_len = scan - idt_handle->names;
 
 	scan++;
 
···
 
 static int xillybus_open(struct inode *inode, struct file *filp)
 {
-	int rc = 0;
+	int rc;
 	unsigned long flags;
-	int minor = iminor(inode);
-	int major = imajor(inode);
-	struct xilly_endpoint *ep_iter, *endpoint = NULL;
+	struct xilly_endpoint *endpoint;
 	struct xilly_channel *channel;
+	int index;
 
-	mutex_lock(&ep_list_lock);
-
-	list_for_each_entry(ep_iter, &list_of_endpoints, ep_list) {
-		if ((ep_iter->major == major) &&
-		    (minor >= ep_iter->lowest_minor) &&
-		    (minor < (ep_iter->lowest_minor +
-			      ep_iter->num_channels))) {
-			endpoint = ep_iter;
-			break;
-		}
-	}
-	mutex_unlock(&ep_list_lock);
-
-	if (!endpoint) {
-		pr_err("xillybus: open() failed to find a device for major=%d and minor=%d\n",
-		       major, minor);
-		return -ENODEV;
-	}
+	rc = xillybus_find_inode(inode, (void **)&endpoint, &index);
+	if (rc)
+		return rc;
 
 	if (endpoint->fatal_error)
 		return -EIO;
 
-	channel = endpoint->channels[1 + minor - endpoint->lowest_minor];
+	channel = endpoint->channels[1 + index];
 	filp->private_data = channel;
 
 	/*
···
 	.poll       = xillybus_poll,
 };
 
-static int xillybus_init_chrdev(struct xilly_endpoint *endpoint,
-				const unsigned char *idt)
-{
-	int rc;
-	dev_t dev;
-	int devnum, i, minor, major;
-	char devname[48];
-	struct device *device;
-
-	rc = alloc_chrdev_region(&dev, 0, /* minor start */
-				 endpoint->num_channels,
-				 xillyname);
-	if (rc) {
-		dev_warn(endpoint->dev, "Failed to obtain major/minors");
-		return rc;
-	}
-
-	endpoint->major = major = MAJOR(dev);
-	endpoint->lowest_minor = minor = MINOR(dev);
-
-	cdev_init(&endpoint->cdev, &xillybus_fops);
-	endpoint->cdev.owner = endpoint->ephw->owner;
-	rc = cdev_add(&endpoint->cdev, MKDEV(major, minor),
-		      endpoint->num_channels);
-	if (rc) {
-		dev_warn(endpoint->dev, "Failed to add cdev. Aborting.\n");
-		goto unregister_chrdev;
-	}
-
-	idt++;
-
-	for (i = minor, devnum = 0;
-	     devnum < endpoint->num_channels;
-	     devnum++, i++) {
-		snprintf(devname, sizeof(devname)-1, "xillybus_%s", idt);
-
-		devname[sizeof(devname)-1] = 0; /* Should never matter */
-
-		while (*idt++)
-			/* Skip to next */;
-
-		device = device_create(xillybus_class,
-				       NULL,
-				       MKDEV(major, i),
-				       NULL,
-				       "%s", devname);
-
-		if (IS_ERR(device)) {
-			dev_warn(endpoint->dev,
-				 "Failed to create %s device. Aborting.\n",
-				 devname);
-			rc = -ENODEV;
-			goto unroll_device_create;
-		}
-	}
-
-	dev_info(endpoint->dev, "Created %d device files.\n",
-		 endpoint->num_channels);
-	return 0; /* succeed */
-
-unroll_device_create:
-	devnum--; i--;
-	for (; devnum >= 0; devnum--, i--)
-		device_destroy(xillybus_class, MKDEV(major, i));
-
-	cdev_del(&endpoint->cdev);
-unregister_chrdev:
-	unregister_chrdev_region(MKDEV(major, minor), endpoint->num_channels);
-
-	return rc;
-}
-
-static void xillybus_cleanup_chrdev(struct xilly_endpoint *endpoint)
-{
-	int minor;
-
-	for (minor = endpoint->lowest_minor;
-	     minor < (endpoint->lowest_minor + endpoint->num_channels);
-	     minor++)
-		device_destroy(xillybus_class, MKDEV(endpoint->major, minor));
-	cdev_del(&endpoint->cdev);
-	unregister_chrdev_region(MKDEV(endpoint->major,
-				       endpoint->lowest_minor),
-				 endpoint->num_channels);
-
-	dev_info(endpoint->dev, "Removed %d device files.\n",
-		 endpoint->num_channels);
-}
-
 struct xilly_endpoint *xillybus_init_endpoint(struct pci_dev *pdev,
 					      struct device *dev,
 					      struct xilly_endpoint_hardware
···
 	if (rc)
 		goto failed_idt;
 
-	/*
-	 * endpoint is now completely configured. We put it on the list
-	 * available to open() before registering the char device(s)
-	 */
+	rc = xillybus_init_chrdev(dev, &xillybus_fops,
+				  endpoint->ephw->owner, endpoint,
+				  idt_handle.names,
+				  idt_handle.names_len,
+				  endpoint->num_channels,
+				  xillyname, false);
 
-	mutex_lock(&ep_list_lock);
-	list_add_tail(&endpoint->ep_list, &list_of_endpoints);
-	mutex_unlock(&ep_list_lock);
-
-	rc = xillybus_init_chrdev(endpoint, idt_handle.idt);
 	if (rc)
-		goto failed_chrdevs;
+		goto failed_idt;
 
 	devres_release_group(dev, bootstrap_resources);
 
 	return 0;
-
-failed_chrdevs:
-	mutex_lock(&ep_list_lock);
-	list_del(&endpoint->ep_list);
-	mutex_unlock(&ep_list_lock);
 
 failed_idt:
 	xilly_quiesce(endpoint);
···
 
 void xillybus_endpoint_remove(struct xilly_endpoint *endpoint)
 {
-	xillybus_cleanup_chrdev(endpoint);
-
-	mutex_lock(&ep_list_lock);
-	list_del(&endpoint->ep_list);
-	mutex_unlock(&ep_list_lock);
+	xillybus_cleanup_chrdev(endpoint, endpoint->dev);
 
 	xilly_quiesce(endpoint);
 
···
 
 static int __init xillybus_init(void)
 {
-	mutex_init(&ep_list_lock);
-
-	xillybus_class = class_create(THIS_MODULE, xillyname);
-	if (IS_ERR(xillybus_class))
-		return PTR_ERR(xillybus_class);
-
 	xillybus_wq = alloc_workqueue(xillyname, 0, 0);
-	if (!xillybus_wq) {
-		class_destroy(xillybus_class);
+	if (!xillybus_wq)
 		return -ENOMEM;
-	}
 
 	return 0;
 }
···
 {
 	/* flush_workqueue() was called for each endpoint released */
 	destroy_workqueue(xillybus_wq);
-
-	class_destroy(xillybus_class);
 }
 
 module_init(xillybus_init);