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SubjectRe: [PATCH] powerpc/vio: use simple dummy struct device as bus parent
On Fri, Sep 27, 2019 at 09:04:02AM -0400, Dan Streetman wrote:
> 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 <ddstreet@canonical.com>
> ---
> 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 :(

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

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