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