xref: /openbmc/linux/drivers/uio/uio_pci_generic.c (revision 8ffdff6a)
1 // SPDX-License-Identifier: GPL-2.0
2 /* uio_pci_generic - generic UIO driver for PCI 2.3 devices
3  *
4  * Copyright (C) 2009 Red Hat, Inc.
5  * Author: Michael S. Tsirkin <mst@redhat.com>
6  *
7  * Since the driver does not declare any device ids, you must allocate
8  * id and bind the device to the driver yourself.  For example:
9  *
10  * # echo "8086 10f5" > /sys/bus/pci/drivers/uio_pci_generic/new_id
11  * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/e1000e/unbind
12  * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/uio_pci_generic/bind
13  * # ls -l /sys/bus/pci/devices/0000:00:19.0/driver
14  * .../0000:00:19.0/driver -> ../../../bus/pci/drivers/uio_pci_generic
15  *
16  * Driver won't bind to devices which do not support the Interrupt Disable Bit
17  * in the command register. All devices compliant to PCI 2.3 (circa 2002) and
18  * all compliant PCI Express devices should support this bit.
19  */
20 
21 #include <linux/device.h>
22 #include <linux/module.h>
23 #include <linux/pci.h>
24 #include <linux/slab.h>
25 #include <linux/uio_driver.h>
26 
27 #define DRIVER_VERSION	"0.01.0"
28 #define DRIVER_AUTHOR	"Michael S. Tsirkin <mst@redhat.com>"
29 #define DRIVER_DESC	"Generic UIO driver for PCI 2.3 devices"
30 
31 struct uio_pci_generic_dev {
32 	struct uio_info info;
33 	struct pci_dev *pdev;
34 };
35 
36 static inline struct uio_pci_generic_dev *
37 to_uio_pci_generic_dev(struct uio_info *info)
38 {
39 	return container_of(info, struct uio_pci_generic_dev, info);
40 }
41 
42 static int release(struct uio_info *info, struct inode *inode)
43 {
44 	struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
45 
46 	/*
47 	 * This driver is insecure when used with devices doing DMA, but some
48 	 * people (mis)use it with such devices.
49 	 * Let's at least make sure DMA isn't left enabled after the userspace
50 	 * driver closes the fd.
51 	 * Note that there's a non-zero chance doing this will wedge the device
52 	 * at least until reset.
53 	 */
54 	pci_clear_master(gdev->pdev);
55 	return 0;
56 }
57 
58 /* Interrupt handler. Read/modify/write the command register to disable
59  * the interrupt. */
60 static irqreturn_t irqhandler(int irq, struct uio_info *info)
61 {
62 	struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
63 
64 	if (!pci_check_and_mask_intx(gdev->pdev))
65 		return IRQ_NONE;
66 
67 	/* UIO core will signal the user process. */
68 	return IRQ_HANDLED;
69 }
70 
71 static int probe(struct pci_dev *pdev,
72 			   const struct pci_device_id *id)
73 {
74 	struct uio_pci_generic_dev *gdev;
75 	int err;
76 
77 	err = pcim_enable_device(pdev);
78 	if (err) {
79 		dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n",
80 			__func__, err);
81 		return err;
82 	}
83 
84 	if (pdev->irq && !pci_intx_mask_supported(pdev))
85 		return -ENOMEM;
86 
87 	gdev = devm_kzalloc(&pdev->dev, sizeof(struct uio_pci_generic_dev), GFP_KERNEL);
88 	if (!gdev)
89 		return -ENOMEM;
90 
91 	gdev->info.name = "uio_pci_generic";
92 	gdev->info.version = DRIVER_VERSION;
93 	gdev->info.release = release;
94 	gdev->pdev = pdev;
95 	if (pdev->irq && (pdev->irq != IRQ_NOTCONNECTED)) {
96 		gdev->info.irq = pdev->irq;
97 		gdev->info.irq_flags = IRQF_SHARED;
98 		gdev->info.handler = irqhandler;
99 	} else {
100 		dev_warn(&pdev->dev, "No IRQ assigned to device: "
101 			 "no support for interrupts?\n");
102 	}
103 
104 	return devm_uio_register_device(&pdev->dev, &gdev->info);
105 }
106 
107 static struct pci_driver uio_pci_driver = {
108 	.name = "uio_pci_generic",
109 	.id_table = NULL, /* only dynamic id's */
110 	.probe = probe,
111 };
112 
113 module_pci_driver(uio_pci_driver);
114 MODULE_VERSION(DRIVER_VERSION);
115 MODULE_LICENSE("GPL v2");
116 MODULE_AUTHOR(DRIVER_AUTHOR);
117 MODULE_DESCRIPTION(DRIVER_DESC);
118