Loading drivers via kldload

David Somayajulu david.somayajulu at qlogic.com
Fri Aug 12 21:20:30 UTC 2011

This is pretty bizarre. I have been experimenting with a very simple driver (see source below) which essentially checks the PCI vendor and Device ID's in the probe routine. The attach and detach are empty functions. When I run kldload and load the driver in a system with HBAs which have a valid Subsytem Vendor and Device ID's, the driver loads and attaches to the functions.

However when the Subsystem Vendor and Device ID's are zero, the system panics and the stack trace is as shown below(FreeBSD 8.2 on amd64 machine). I don't understand why ata_pci_attach() is getting invoked. I even put a panic() call at the top of qla_pci_probe(), and noticed that it wasn't getting invoked!

panic: resource_list_alloc: resource_ entry is busy

0xFFFFFFFF805F4E0E      at kdb_backtrace+0x5E
0xFFFFFFFF805C2D07      at panic+0x187
0xFFFFFFFF805F0616      at resource_list_alloc+0x1C6
0xFFFFFFFF804450F7      at pci_alloc_resource+0x147
0xFFFFFFFF805F0439      at bus_alloc_resource+0x89
0xFFFFFFFF8027A467      at ata_pci_attach+0xE7
0xFFFFFFFF805EEA09      at device_attach+0x69
0xFFFFFFFF80447ACA      at pci_driver_added+0xDA
0xFFFFFFFF805ECD55      at devclass_driver_added+0x75
0xFFFFFFFF805EE715      at driver_module_handler+0x165
0xFFFFFFFF805B24B8      at module_register_init+0xB8
0xFFFFFFFF805AADB6      at linker_load_module+0x996
0xFFFFFFFF805AB6C4      at kern_kldload+0xB4
0xFFFFFFFF805AB894      at kldload+0x84
0xFFFFFFFF80600DD5      at syscallenter+0x1E5
0xFFFFFFFF808ACA5B      at syscall+0x4B
0xFFFFFFFF80895292      at Xfast_syscall+0xE2

============= Source Code ========
//#includes deleted
// file: qla_os.c

static int qla_pci_probe (device_t);
static int qla_pci_attach (device_t);
static int qla_pci_detach (device_t);

static device_method_t qla_pci_methods[] = {
        /* Device interface */
        DEVMETHOD(device_probe, qla_pci_probe),
        DEVMETHOD(device_attach, qla_pci_attach),
        DEVMETHOD(device_detach, qla_pci_detach),
        { 0, 0 }

static driver_t qla_pci_driver = {
        "qltest", qla_pci_methods, sizeof (uint64_t),

static devclass_t qla_devclass;
MODULE_VERSION(qltest, 1);
DRIVER_MODULE(qltest, pci, qla_pci_driver, qla_devclass, 0, 0);

char dev_str[50];
 * Name:        qla_pci_probe
static int
qla_pci_probe(device_t dev)
        int i;

        // I put call to panic() here and
        // it did not get invoked when Subsytem Vendor/DeviceIDs were zeros

        switch ((pci_get_device(dev) << 16) | (pci_get_vendor(dev))) {

        case ((QLA_PCI_DEVICEID << 16) | 0x1077):
                sprintf(dev_str, "%s ","Qlogic Adapter");
                device_set_desc(dev, dev_str);
                device_printf(dev, "%s: Invalid Device[0x%04x: 0x%04x]\n",
                        __func__, pci_get_vendor(dev), pci_get_device(dev));
                return (ENXIO);
        return (0);

static int
qla_pci_attach(device_t dev)
        device_printf(dev, "%s: called\n", __func__);
        return 0;

static int
qla_pci_detach(device_t dev)
        device_printf(dev, "%s: called\n", __func__);
        return (0);

============= Makefile =============
SRCS+= device_if.h bus_if.h pci_if.h

        rm -f opt_bdg.h device_if.h bus_if.h pci_if.h export_syms
        rm -f *.o *.kld *.ko
        rm -f @ machine

.include <bsd.kmod.mk>


david S.

-----Original Message-----
From: Stanislav Sedov [mailto:stas at FreeBSD.org]
Sent: Thursday, August 11, 2011 11:48 PM
To: David Somayajulu
Cc: freebsd-current at freebsd.org
Subject: Re: Loading drivers via kldload

On Thu, 11 Aug 2011 17:08:30 -0700
David Somayajulu <david.somayajulu at qlogic.com> mentioned:

> Hi All,
> While loading PCIe based HBA drivers via kldload, does FreeBSD expect a valid (i.e., non-zero)  PCI subsystem Vendor and Device IDs?

It depends on the specific driver.  FreeBSD doesn't check for the PCI ID
in general.  Usually, drivers contains a routine that check if this driver
can be used with that hardware based on the PCI ID.

Stanislav Sedov

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