--- load kprobe module
 [  578.019386] [size] plant jprobe at ffffffff803477c0, handler addr ffffffff88838160
 [  578.019556] [size] plant jprobe at ffffffff80347720, handler addr ffffffff888380d0
 [  578.019710] [size] plant jprobe at ffffffff80347680, handler addr ffffffff88838040

--- load sound modules
 [  582.117327] -- pci_write_config_word(): *0x0054 := 0x00000000
 [  582.117348] ACPI: PCI Interrupt 0000:00:1b.0[A] -> GSI 22 (level, low) -> IRQ 22
 [  582.117727] -- pci_write_config_word(): *0x0004 := 0x00000006
 [  582.117739] PCI: Setting latency timer of device 0000:00:1b.0 to 64
 [  582.117744] -- pci_write_config_byte(): *0x000d := 0x00000040
 [  582.118149] -- azx_init_stream
 [  582.118155] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_stream()
 [  582.118162] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_create()
 [  582.118169] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_chip()
 [  582.118177] -- pci_write_config_byte(): *0x0044 := 0x00000000
 [  582.118186] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_chip()
 [  582.149394] ALSA sound/pci/hda/hda_intel.c:717: codec_mask = 0x3
 [  582.149404] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_chip()
 [  582.149413] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_chip()
 [  582.149421] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_chip()
 [  582.149431] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_create()
 [  582.269214] ALSA sound/pci/hda/hda_codec.c:1751: hda_codec: PCI 104d:81ef, codec config 0 is selected
 [  582.357068] -- stac92xx_init

--- suspend

 [  602.566734] HDA Intel 0000:00:1b.0: suspend
 [  602.566738] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_suspend()
 [  602.566742] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_suspend()
 [  602.566747] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_suspend()
 [  602.574242] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_suspend()
 [  602.574249] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_suspend()
 [  602.574254] -- pci_write_config_word(): *0x0004 := 0x00000002
 [  602.574259] ACPI: PCI interrupt for device 0000:00:1b.0 disabled
 [  602.574262] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_suspend()
 [  602.574335] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_suspend()
 [  602.574350] -- pci_write_config_word(): *0x0054 := 0x00000003

--- resume

 [    3.586318] HDA Intel 0000:00:1b.0: resuming
 [    3.586332] -- pci_write_config_word(): *0x0054 := 0x00000000
 [    3.602055] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x07 in azx_resume()
 [    3.602093] PM: Writing back config space on device 0000:00:1b.0 at offset 3 (was 0, writing 10)
 [    3.602098] -- pci_write_config_dword(): *0x000c := 0x00000010
 [    3.602109] PM: Writing back config space on device 0000:00:1b.0 at offset 1 (was 100006, writing 100002)
 [    3.602114] -- pci_write_config_dword(): *0x0004 := 0x00100002
 [    3.602146] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x07 in azx_resume()
 [    3.602154] ACPI: PCI Interrupt 0000:00:1b.0[A] -> GSI 22 (level, low) -> IRQ 22
 [    3.602161] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x07 in azx_resume()
 [    3.602168] -- pci_write_config_word(): *0x0004 := 0x00000006
 [    3.602176] PCI: Setting latency timer of device 0000:00:1b.0 to 64
 [    3.602180] -- pci_write_config_byte(): *0x000d := 0x00000040
 [    3.602189] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x07 in azx_resume()
 [    3.602204] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x07 in azx_init_chip()
 [    3.602211] -- pci_write_config_byte(): *0x0044 := 0x00000000
 [    3.602219] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_chip()
 [    3.626017] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_chip()
 [    3.626025] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_chip()
 [    3.626032] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_init_chip()
 [    3.645983] -- stac92xx_resume
 [    3.645985] -- stac92xx_init
 [    3.646000] -- stac92xx_set_config_regs
 [    3.665954] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_resume()
 [    3.665960] ALSA sound/pci/hda/hda_intel.c:412: TCSEL=0x00 in azx_resume()

# pcitweak -r 00:1b:0 -b 0x44
0x07
# pcitweak -w 00:1b:0 -b 0x44 0
# pcitweak -r 00:1b:0 -b 0x44
0x00

(no jprobe messages for pcitweak)

--- kprobe module code

/* jprobebio.c
   Will Cohen, adapted for pci tracing by Willem van Engen
   source: http://www.redhat.com/magazine/005mar05/features/kprobes/
*/

#include <linux/module.h>
#include <linux/kprobes.h>
#include <linux/pci.h>

#define LOG_2_BINS 8
#define BINS (1<<LOG_2_BINS)

#define INST_PCI_OP_WRITE(size,type,len) \
static void inst_pci_write_config_##size(struct pci_bus *bus, unsigned int devfn, int pos, type value) \
{ \
  if (!bus) { printk("-- ERR: !bus\n"); jprobe_return(); } \
  if (bus->number==0 && devfn==0xd8) { \
    printk("-- pci_write_config_%s(): *0x%04x := 0x%08x\n", #size,pos,value); \
  } \
  \
  jprobe_return(); \
} \
static struct jprobe my_jprobe_##size = { \
    .kp.addr = (kprobe_opcode_t *) pci_bus_write_config_##size, \
    .entry = (kprobe_opcode_t *) inst_pci_write_config_##size \
}; \

INST_PCI_OP_WRITE(byte, u8, 1)
INST_PCI_OP_WRITE(word, u16, 2)
INST_PCI_OP_WRITE(dword, u32, 4)

#define PLANT_PROBE(size) \
    register_jprobe(&my_jprobe_##size); \
    printk("[%s] plant jprobe at %p, handler addr %p\n", "size", my_jprobe_##size.kp.addr, my_jprobe_##size.entry);
#define REMOVE_PROBE(size) \
    unregister_jprobe(&my_jprobe_##size);

int init_module(void)
{
    PLANT_PROBE(byte)
    PLANT_PROBE(word)
    PLANT_PROBE(dword)
    return 0;
}

void cleanup_module(void)
{
    REMOVE_PROBE(byte)
    REMOVE_PROBE(word)
    REMOVE_PROBE(dword)
    printk("jprobe unregistered\n");
}

MODULE_LICENSE("GPL");