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/slab.h> 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 33 struct uio_pci_generic_dev { 34 struct uio_info info; 35 struct pci_dev *pdev; 36 spinlock_t lock; /* guards command register accesses */ 37 }; 38 39 static inline struct uio_pci_generic_dev * 40 to_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. */ 47 static 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; 83 done: 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. */ 93 static 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); 120 err: 121 pci_unblock_user_cfg_access(pdev); 122 return err; 123 } 124 125 static 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 err = pci_enable_device(pdev); 132 if (err) { 133 dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n", 134 __func__, err); 135 return err; 136 } 137 138 if (!pdev->irq) { 139 dev_warn(&pdev->dev, "No IRQ assigned to device: " 140 "no support for interrupts?\n"); 141 pci_disable_device(pdev); 142 return -ENODEV; 143 } 144 145 err = verify_pci_2_3(pdev); 146 if (err) 147 goto err_verify; 148 149 gdev = kzalloc(sizeof(struct uio_pci_generic_dev), GFP_KERNEL); 150 if (!gdev) { 151 err = -ENOMEM; 152 goto err_alloc; 153 } 154 155 gdev->info.name = "uio_pci_generic"; 156 gdev->info.version = DRIVER_VERSION; 157 gdev->info.irq = pdev->irq; 158 gdev->info.irq_flags = IRQF_SHARED; 159 gdev->info.handler = irqhandler; 160 gdev->pdev = pdev; 161 spin_lock_init(&gdev->lock); 162 163 if (uio_register_device(&pdev->dev, &gdev->info)) 164 goto err_register; 165 pci_set_drvdata(pdev, gdev); 166 167 return 0; 168 err_register: 169 kfree(gdev); 170 err_alloc: 171 err_verify: 172 pci_disable_device(pdev); 173 return err; 174 } 175 176 static void remove(struct pci_dev *pdev) 177 { 178 struct uio_pci_generic_dev *gdev = pci_get_drvdata(pdev); 179 180 uio_unregister_device(&gdev->info); 181 pci_disable_device(pdev); 182 kfree(gdev); 183 } 184 185 static struct pci_driver driver = { 186 .name = "uio_pci_generic", 187 .id_table = NULL, /* only dynamic id's */ 188 .probe = probe, 189 .remove = remove, 190 }; 191 192 static int __init init(void) 193 { 194 pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n"); 195 return pci_register_driver(&driver); 196 } 197 198 static void __exit cleanup(void) 199 { 200 pci_unregister_driver(&driver); 201 } 202 203 module_init(init); 204 module_exit(cleanup); 205 206 MODULE_VERSION(DRIVER_VERSION); 207 MODULE_LICENSE("GPL v2"); 208 MODULE_AUTHOR(DRIVER_AUTHOR); 209 MODULE_DESCRIPTION(DRIVER_DESC); 210