/* uio_pci_generic - generic UIO driver for PCI 2.3 devices * * Copyright (C) 2009 Red Hat, Inc. * Author: Michael S. Tsirkin <mst@redhat.com> * * This work is licensed under the terms of the GNU GPL, version 2. * * Since the driver does not declare any device ids, you must allocate * id and bind the device to the driver yourself. For example: * * # echo "8086 10f5" > /sys/bus/pci/drivers/uio_pci_generic/new_id * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/e1000e/unbind * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/uio_pci_generic/bind * # ls -l /sys/bus/pci/devices/0000:00:19.0/driver * .../0000:00:19.0/driver -> ../../../bus/pci/drivers/uio_pci_generic * * Driver won't bind to devices which do not support the Interrupt Disable Bit * in the command register. All devices compliant to PCI 2.3 (circa 2002) and * all compliant PCI Express devices should support this bit. */ #include <linux/device.h> #include <linux/module.h> #include <linux/pci.h> #include <linux/uio_driver.h> #include <linux/spinlock.h> #define DRIVER_VERSION "0.01.0" #define DRIVER_AUTHOR "Michael S. Tsirkin <mst@redhat.com>" #define DRIVER_DESC "Generic UIO driver for PCI 2.3 devices" struct uio_pci_generic_dev { struct uio_info info; struct pci_dev *pdev; spinlock_t lock; /* guards command register accesses */ }; static inline struct uio_pci_generic_dev * to_uio_pci_generic_dev(struct uio_info *info) { return container_of(info, struct uio_pci_generic_dev, info); } /* Interrupt handler. Read/modify/write the command register to disable * the interrupt. */ static irqreturn_t irqhandler(int irq, struct uio_info *info) { struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info); struct pci_dev *pdev = gdev->pdev; irqreturn_t ret = IRQ_NONE; u32 cmd_status_dword; u16 origcmd, newcmd, status; /* We do a single dword read to retrieve both command and status. * Document assumptions that make this possible. */ BUILD_BUG_ON(PCI_COMMAND % 4); BUILD_BUG_ON(PCI_COMMAND + 2 != PCI_STATUS); spin_lock_irq(&gdev->lock); pci_block_user_cfg_access(pdev); /* Read both command and status registers in a single 32-bit operation. * Note: we could cache the value for command and move the status read * out of the lock if there was a way to get notified of user changes * to command register through sysfs. Should be good for shared irqs. */ pci_read_config_dword(pdev, PCI_COMMAND, &cmd_status_dword); origcmd = cmd_status_dword; status = cmd_status_dword >> 16; /* Check interrupt status register to see whether our device * triggered the interrupt. */ if (!(status & PCI_STATUS_INTERRUPT)) goto done; /* We triggered the interrupt, disable it. */ newcmd = origcmd | PCI_COMMAND_INTX_DISABLE; if (newcmd != origcmd) pci_write_config_word(pdev, PCI_COMMAND, newcmd); /* UIO core will signal the user process. */ ret = IRQ_HANDLED; done: pci_unblock_user_cfg_access(pdev); spin_unlock_irq(&gdev->lock); return ret; } /* Verify that the device supports Interrupt Disable bit in command register, * per PCI 2.3, by flipping this bit and reading it back: this bit was readonly * in PCI 2.2. */ static int __devinit verify_pci_2_3(struct pci_dev *pdev) { u16 orig, new; int err = 0; pci_block_user_cfg_access(pdev); pci_read_config_word(pdev, PCI_COMMAND, &orig); pci_write_config_word(pdev, PCI_COMMAND, orig ^ PCI_COMMAND_INTX_DISABLE); pci_read_config_word(pdev, PCI_COMMAND, &new); /* There's no way to protect against * hardware bugs or detect them reliably, but as long as we know * what the value should be, let's go ahead and check it. */ if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) { err = -EBUSY; dev_err(&pdev->dev, "Command changed from 0x%x to 0x%x: " "driver or HW bug?\n", orig, new); goto err; } if (!((new ^ orig) & PCI_COMMAND_INTX_DISABLE)) { dev_warn(&pdev->dev, "Device does not support " "disabling interrupts: unable to bind.\n"); err = -ENODEV; goto err; } /* Now restore the original value. */ pci_write_config_word(pdev, PCI_COMMAND, orig); err: pci_unblock_user_cfg_access(pdev); return err; } static int __devinit probe(struct pci_dev *pdev, const struct pci_device_id *id) { struct uio_pci_generic_dev *gdev; int err; if (!pdev->irq) { dev_warn(&pdev->dev, "No IRQ assigned to device: " "no support for interrupts?\n"); return -ENODEV; } err = pci_enable_device(pdev); if (err) { dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n", __func__, err); return err; } err = verify_pci_2_3(pdev); if (err) goto err_verify; gdev = kzalloc(sizeof(struct uio_pci_generic_dev), GFP_KERNEL); if (!gdev) { err = -ENOMEM; goto err_alloc; } gdev->info.name = "uio_pci_generic"; gdev->info.version = DRIVER_VERSION; gdev->info.irq = pdev->irq; gdev->info.irq_flags = IRQF_SHARED; gdev->info.handler = irqhandler; gdev->pdev = pdev; spin_lock_init(&gdev->lock); if (uio_register_device(&pdev->dev, &gdev->info)) goto err_register; pci_set_drvdata(pdev, gdev); return 0; err_register: kfree(gdev); err_alloc: err_verify: pci_disable_device(pdev); return err; } static void remove(struct pci_dev *pdev) { struct uio_pci_generic_dev *gdev = pci_get_drvdata(pdev); uio_unregister_device(&gdev->info); pci_disable_device(pdev); kfree(gdev); } static struct pci_driver driver = { .name = "uio_pci_generic", .id_table = NULL, /* only dynamic id's */ .probe = probe, .remove = remove, }; static int __init init(void) { pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n"); return pci_register_driver(&driver); } static void __exit cleanup(void) { pci_unregister_driver(&driver); } module_init(init); module_exit(cleanup); MODULE_VERSION(DRIVER_VERSION); MODULE_LICENSE("GPL v2"); MODULE_AUTHOR(DRIVER_AUTHOR); MODULE_DESCRIPTION(DRIVER_DESC);