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