Chapter 11. PCI Devices
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## Chapter 11. PCI Devices

This chapter will talk about the FreeBSD mechanisms for writing a device driver for a device on a PCI bus.

## 11.1. Probe and Attach

Information here about how the PCI bus code iterates through the unattached devices and see if a newly loaded kld will attach to any of them.

### 11.1.1. Sample Driver Source (`mypci.c`)

/* * Simple KLD to play with the PCI functions. * * Murray Stokely */ #include <sys/param.h> /* defines used in kernel.h */ #include <sys/module.h> #include <sys/systm.h> #include <sys/errno.h> #include <sys/kernel.h> /* types used in module initialization */ #include <sys/conf.h> /* cdevsw struct */ #include <sys/uio.h> /* uio struct */ #include <sys/malloc.h> #include <sys/bus.h> /* structs, prototypes for pci bus stuff and DEVMETHOD macros! */ #include <machine/bus.h> #include <sys/rman.h> #include <machine/resource.h> #include <dev/pci/pcivar.h> /* For pci_get macros! */ #include <dev/pci/pcireg.h> /* The softc holds our per-instance data. */ struct mypci_softc { device_t my_dev; struct cdev *my_cdev; }; /* Function prototypes */ static d_open_t mypci_open; static d_close_t mypci_close; static d_read_t mypci_read; static d_write_t mypci_write; /* Character device entry points */ static struct cdevsw mypci_cdevsw = { .d_version = D_VERSION, .d_open = mypci_open, .d_close = mypci_close, .d_read = mypci_read, .d_write = mypci_write, .d_name = "mypci", }; /* * In the cdevsw routines, we find our softc by using the si_drv1 member * of struct cdev. We set this variable to point to our softc in our * attach routine when we create the /dev entry. */ int mypci_open(struct cdev *dev, int oflags, int devtype, d_thread_t *td) { struct mypci_softc *sc; /* Look up our softc. */ sc = dev->si_drv1; device_printf(sc->my_dev, "Opened successfully.\n"); return (0); } int mypci_close(struct cdev *dev, int fflag, int devtype, d_thread_t *td) { struct mypci_softc *sc; /* Look up our softc. */ sc = dev->si_drv1; device_printf(sc->my_dev, "Closed.\n"); return (0); } int mypci_read(struct cdev *dev, struct uio *uio, int ioflag) { struct mypci_softc *sc; /* Look up our softc. */ sc = dev->si_drv1; device_printf(sc->my_dev, "Asked to read %d bytes.\n", uio->uio_resid); return (0); } int mypci_write(struct cdev *dev, struct uio *uio, int ioflag) { struct mypci_softc *sc; /* Look up our softc. */ sc = dev->si_drv1; device_printf(sc->my_dev, "Asked to write %d bytes.\n", uio->uio_resid); return (0); } /* PCI Support Functions */ /* * Compare the device ID of this device against the IDs that this driver * supports. If there is a match, set the description and return success. */ static int mypci_probe(device_t dev) { device_printf(dev, "MyPCI Probe\nVendor ID : 0x%x\nDevice ID : 0x%x\n", pci_get_vendor(dev), pci_get_device(dev)); if (pci_get_vendor(dev) == 0x11c1) { printf("We've got the Winmodem, probe successful!\n"); device_set_desc(dev, "WinModem"); return (BUS_PROBE_DEFAULT); } return (ENXIO); } /* Attach function is only called if the probe is successful. */ static int mypci_attach(device_t dev) { struct mypci_softc *sc; printf("MyPCI Attach for : deviceID : 0x%x\n", pci_get_devid(dev)); /* Look up our softc and initialize its fields. */ sc = device_get_softc(dev); sc->my_dev = dev; /* * Create a /dev entry for this device. The kernel will assign us * a major number automatically. We use the unit number of this * device as the minor number and name the character device * "mypci<unit>". */ sc->my_cdev = make_dev(`&`mypci_cdevsw, device_get_unit(dev), UID_ROOT, GID_WHEEL, 0600, "mypci%u", device_get_unit(dev)); sc->my_cdev->si_drv1 = sc; printf("Mypci device loaded.\n"); return (0); } /* Detach device. */ static int mypci_detach(device_t dev) { struct mypci_softc *sc; /* Teardown the state in our softc created in our attach routine. */ sc = device_get_softc(dev); destroy_dev(sc->my_cdev); printf("Mypci detach!\n"); return (0); } /* Called during system shutdown after sync. */ static int mypci_shutdown(device_t dev) { printf("Mypci shutdown!\n"); return (0); } /* * Device suspend routine. */ static int mypci_suspend(device_t dev) { printf("Mypci suspend!\n"); return (0); } /* * Device resume routine. */ static int mypci_resume(device_t dev) { printf("Mypci resume!\n"); return (0); } static device_method_t mypci_methods[] = { /* Device interface */ DEVMETHOD(device_probe, mypci_probe), DEVMETHOD(device_attach, mypci_attach), DEVMETHOD(device_detach, mypci_detach), DEVMETHOD(device_shutdown, mypci_shutdown), DEVMETHOD(device_suspend, mypci_suspend), DEVMETHOD(device_resume, mypci_resume), DEVMETHOD_END }; static devclass_t mypci_devclass; DEFINE_CLASS_0(mypci, mypci_driver, mypci_methods, sizeof(struct mypci_softc)); DRIVER_MODULE(mypci, pci, mypci_driver, mypci_devclass, 0, 0);

### 11.1.2. `Makefile` for Sample Driver

# Makefile for mypci driver KMOD= mypci SRCS= mypci.c SRCS+= device_if.h bus_if.h pci_if.h .include <bsd.kmod.mk>

If you place the above source file and `Makefile` into a directory, you may run `make` to compile the sample driver. Additionally, you may run `make load` to load the driver into the currently running kernel and `make unload` to unload the driver after it is loaded.

### 11.1.3. Additional Resources

- PCI Special Interest Group
- PCI System Architecture, Fourth Edition by Tom Shanley, et al.

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