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1/* uio_pci_generic - generic UIO driver for PCI 2.3 devices
2 *
3 * Copyright (C) 2009 Red Hat, Inc.
4 * Author: Michael S. Tsirkin <mst@redhat.com>
5 *
6 * This work is licensed under the terms of the GNU GPL, version 2.
7 *
8 * Since the driver does not declare any device ids, you must allocate
9 * id and bind the device to the driver yourself. For example:
10 *
11 * # echo "8086 10f5" > /sys/bus/pci/drivers/uio_pci_generic/new_id
12 * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/e1000e/unbind
13 * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/uio_pci_generic/bind
14 * # ls -l /sys/bus/pci/devices/0000:00:19.0/driver
15 * .../0000:00:19.0/driver -> ../../../bus/pci/drivers/uio_pci_generic
16 *
17 * Driver won't bind to devices which do not support the Interrupt Disable Bit
18 * in the command register. All devices compliant to PCI 2.3 (circa 2002) and
19 * all compliant PCI Express devices should support this bit.
20 */
21
22#include <linux/device.h>
23#include <linux/module.h>
24#include <linux/pci.h>
5a0e3ad6 25#include <linux/slab.h>
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26#include <linux/uio_driver.h>
27#include <linux/spinlock.h>
28
29#define DRIVER_VERSION "0.01.0"
30#define DRIVER_AUTHOR "Michael S. Tsirkin <mst@redhat.com>"
31#define DRIVER_DESC "Generic UIO driver for PCI 2.3 devices"
32
33struct uio_pci_generic_dev {
34 struct uio_info info;
35 struct pci_dev *pdev;
36 spinlock_t lock; /* guards command register accesses */
37};
38
39static inline struct uio_pci_generic_dev *
40to_uio_pci_generic_dev(struct uio_info *info)
41{
42 return container_of(info, struct uio_pci_generic_dev, info);
43}
44
45/* Interrupt handler. Read/modify/write the command register to disable
46 * the interrupt. */
47static irqreturn_t irqhandler(int irq, struct uio_info *info)
48{
49 struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
50 struct pci_dev *pdev = gdev->pdev;
51 irqreturn_t ret = IRQ_NONE;
52 u32 cmd_status_dword;
53 u16 origcmd, newcmd, status;
54
55 /* We do a single dword read to retrieve both command and status.
56 * Document assumptions that make this possible. */
57 BUILD_BUG_ON(PCI_COMMAND % 4);
58 BUILD_BUG_ON(PCI_COMMAND + 2 != PCI_STATUS);
59
60 spin_lock_irq(&gdev->lock);
61 pci_block_user_cfg_access(pdev);
62
63 /* Read both command and status registers in a single 32-bit operation.
64 * Note: we could cache the value for command and move the status read
65 * out of the lock if there was a way to get notified of user changes
66 * to command register through sysfs. Should be good for shared irqs. */
67 pci_read_config_dword(pdev, PCI_COMMAND, &cmd_status_dword);
68 origcmd = cmd_status_dword;
69 status = cmd_status_dword >> 16;
70
71 /* Check interrupt status register to see whether our device
72 * triggered the interrupt. */
73 if (!(status & PCI_STATUS_INTERRUPT))
74 goto done;
75
76 /* We triggered the interrupt, disable it. */
77 newcmd = origcmd | PCI_COMMAND_INTX_DISABLE;
78 if (newcmd != origcmd)
79 pci_write_config_word(pdev, PCI_COMMAND, newcmd);
80
81 /* UIO core will signal the user process. */
82 ret = IRQ_HANDLED;
83done:
84
85 pci_unblock_user_cfg_access(pdev);
86 spin_unlock_irq(&gdev->lock);
87 return ret;
88}
89
90/* Verify that the device supports Interrupt Disable bit in command register,
91 * per PCI 2.3, by flipping this bit and reading it back: this bit was readonly
92 * in PCI 2.2. */
93static int __devinit verify_pci_2_3(struct pci_dev *pdev)
94{
95 u16 orig, new;
96 int err = 0;
97
98 pci_block_user_cfg_access(pdev);
99 pci_read_config_word(pdev, PCI_COMMAND, &orig);
100 pci_write_config_word(pdev, PCI_COMMAND,
101 orig ^ PCI_COMMAND_INTX_DISABLE);
102 pci_read_config_word(pdev, PCI_COMMAND, &new);
103 /* There's no way to protect against
104 * hardware bugs or detect them reliably, but as long as we know
105 * what the value should be, let's go ahead and check it. */
106 if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) {
107 err = -EBUSY;
108 dev_err(&pdev->dev, "Command changed from 0x%x to 0x%x: "
109 "driver or HW bug?\n", orig, new);
110 goto err;
111 }
112 if (!((new ^ orig) & PCI_COMMAND_INTX_DISABLE)) {
113 dev_warn(&pdev->dev, "Device does not support "
114 "disabling interrupts: unable to bind.\n");
115 err = -ENODEV;
116 goto err;
117 }
118 /* Now restore the original value. */
119 pci_write_config_word(pdev, PCI_COMMAND, orig);
120err:
121 pci_unblock_user_cfg_access(pdev);
122 return err;
123}
124
125static int __devinit probe(struct pci_dev *pdev,
126 const struct pci_device_id *id)
127{
128 struct uio_pci_generic_dev *gdev;
129 int err;
130
131 if (!pdev->irq) {
132 dev_warn(&pdev->dev, "No IRQ assigned to device: "
133 "no support for interrupts?\n");
134 return -ENODEV;
135 }
136
137 err = pci_enable_device(pdev);
138 if (err) {
139 dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n",
140 __func__, err);
141 return err;
142 }
143
144 err = verify_pci_2_3(pdev);
145 if (err)
146 goto err_verify;
147
148 gdev = kzalloc(sizeof(struct uio_pci_generic_dev), GFP_KERNEL);
149 if (!gdev) {
150 err = -ENOMEM;
151 goto err_alloc;
152 }
153
154 gdev->info.name = "uio_pci_generic";
155 gdev->info.version = DRIVER_VERSION;
156 gdev->info.irq = pdev->irq;
157 gdev->info.irq_flags = IRQF_SHARED;
158 gdev->info.handler = irqhandler;
159 gdev->pdev = pdev;
160 spin_lock_init(&gdev->lock);
161
162 if (uio_register_device(&pdev->dev, &gdev->info))
163 goto err_register;
164 pci_set_drvdata(pdev, gdev);
165
166 return 0;
167err_register:
168 kfree(gdev);
169err_alloc:
170err_verify:
171 pci_disable_device(pdev);
172 return err;
173}
174
175static void remove(struct pci_dev *pdev)
176{
177 struct uio_pci_generic_dev *gdev = pci_get_drvdata(pdev);
178
179 uio_unregister_device(&gdev->info);
180 pci_disable_device(pdev);
181 kfree(gdev);
182}
183
184static struct pci_driver driver = {
185 .name = "uio_pci_generic",
186 .id_table = NULL, /* only dynamic id's */
187 .probe = probe,
188 .remove = remove,
189};
190
191static int __init init(void)
192{
193 pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
194 return pci_register_driver(&driver);
195}
196
197static void __exit cleanup(void)
198{
199 pci_unregister_driver(&driver);
200}
201
202module_init(init);
203module_exit(cleanup);
204
205MODULE_VERSION(DRIVER_VERSION);
206MODULE_LICENSE("GPL v2");
207MODULE_AUTHOR(DRIVER_AUTHOR);
208MODULE_DESCRIPTION(DRIVER_DESC);