On Fri, Sep 27, 2019 at 2:19 PM Greg Kroah-Hartman
[off-list ref] wrote:

On Fri, Sep 27, 2019 at 09:04:02AM -0400, Dan Streetman wrote:

quoted

The dummy vio_bus_device creates the /sys/devices/vio directory, which
contains real vio devices under it; since it represents itself as having
a bus = &vio_bus_type, its /sys/devices/vio/uevent does call the bus's
.uevent function, vio_hotplug(), and as that function won't find a real
device for the dummy vio_dev, it will return -ENODEV.

One of the main users of the uevent node is udevadm, e.g. when it is called
with 'udevadm trigger --devices'.  Up until recently, it would ignore any
errors returned when writing to devices' uevent file, but it was recently
changed to start returning error if it gets an error writing to any uevent
file:
https://github.com/systemd/systemd/commit/97afc0351a96e0daa83964df33937967c75c644f

since the /sys/devices/vio/uevent file has always returned ENODEV from
any write to it, this now causes the udevadm trigger command to return
an error.  This may be fixed in udevadm to ignore ENODEV errors, but the
vio driver should still be fixed.

This patch changes the arch/powerpc/platform/pseries/vio.c 'dummy'
parent device into a real dummy device with no .bus, so its uevent
file will stop returning ENODEV and simply do nothing and return 0.

Signed-off-by: Dan Streetman <redacted>
---
 arch/powerpc/platforms/pseries/vio.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/vio.c b/arch/powerpc/platforms/pseries/vio.c
index 79e2287991db..63bc16631680 100644
--- a/arch/powerpc/platforms/pseries/vio.c
+++ b/arch/powerpc/platforms/pseries/vio.c

@@ -32,11 +32,8 @@
 #include <asm/page.h>
 #include <asm/hvcall.h>

-static struct vio_dev vio_bus_device  = { /* fake "parent" device */
-     .name = "vio",
-     .type = "",
-     .dev.init_name = "vio",
-     .dev.bus = &vio_bus_type,
+static struct device vio_bus = {
+     .init_name      = "vio",

Eeek, no!  Why are you creating a static device that will then be
reference counted?  Not nice :(

so, I looked again and it seems quite a few places appear to do
exactly this, is it something that should be fixed?

$ git grep 'static struct device [^*{]*{'
arch/arm/kernel/dma-isa.c:static struct device isa_dma_dev = {
arch/arm/mach-rpc/dma.c:static struct device isa_dma_dev = {
arch/arm/mach-s3c24xx/s3c2410.c:static struct device s3c2410_dev = {
arch/arm/mach-s3c24xx/s3c2412.c:static struct device s3c2412_dev = {
arch/arm/mach-s3c24xx/s3c2416.c:static struct device s3c2416_dev = {
arch/arm/mach-s3c24xx/s3c2440.c:static struct device s3c2440_dev = {
arch/arm/mach-s3c24xx/s3c2442.c:static struct device s3c2442_dev = {
arch/arm/mach-s3c24xx/s3c2443.c:static struct device s3c2443_dev = {
arch/arm/mach-s3c64xx/common.c:static struct device s3c64xx_dev = {
arch/arm/mach-s3c64xx/s3c6400.c:static struct device s3c6400_dev = {
arch/arm/mach-s3c64xx/s3c6410.c:static struct device s3c6410_dev = {
arch/mips/sgi-ip22/ip22-gio.c:static struct device gio_bus = {
arch/parisc/kernel/drivers.c:static struct device root = {
arch/powerpc/platforms/ps3/system-bus.c:static struct device ps3_system_bus = {
arch/powerpc/platforms/pseries/ibmebus.c:static struct device
ibmebus_bus_device = { /* fake "parent" device */
arch/powerpc/platforms/pseries/vio.c:static struct device vio_bus = {
arch/um/drivers/virtio_uml.c:static struct device vu_cmdline_parent = {
drivers/base/isa.c:static struct device isa_bus = {
drivers/block/rbd.c:static struct device rbd_root_dev = {
drivers/gpu/drm/ttm/ttm_module.c:static struct device ttm_drm_class_device = {
drivers/iio/dummy/iio_dummy_evgen.c:static struct device iio_evgen_dev = {
drivers/iio/trigger/iio-trig-sysfs.c:static struct device iio_sysfs_trig_dev = {
drivers/misc/sgi-gru/grumain.c:static struct device gru_device = {
drivers/nubus/bus.c:static struct device nubus_parent = {
drivers/sh/maple/maple.c:static struct device maple_bus = {
drivers/sh/superhyway/superhyway.c:static struct device
superhyway_bus_device = {
drivers/soc/fsl/qe/qe_ic.c:static struct device device_qe_ic = {
drivers/virtio/virtio_mmio.c:static struct device vm_cmdline_parent = {
kernel/time/clockevents.c:static struct device tick_bc_dev = {
kernel/time/clocksource.c:static struct device device_clocksource = {

What's wrong with a simple call to device_create() for your "fake"
device you want to make here?  That's what it is there for :)

thanks,

greg k-h