linux-kernel - [PATCH] powerpc/vio: use simple dummy struct device as bus parent

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Date:   Fri, 27 Sep 2019 09:04:02 -0400
From:   Dan Streetman <ddstreet@...onical.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Dan Streetman <ddstreet@...onical.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Rob Herring <robh@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH] powerpc/vio: use simple dummy struct device as bus parent

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@...onical.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",
 };

 #ifdef CONFIG_PPC_SMLPAR
@@ -1412,7 +1409,7 @@ struct vio_dev *vio_register_device_node(struct device_node *of_node)
 	set_dev_node(&viodev->dev, of_node_to_nid(of_node));

 	/* init generic 'struct device' fields: */
-	viodev->dev.parent = &vio_bus_device.dev;
+	viodev->dev.parent = &vio_bus;
 	viodev->dev.bus = &vio_bus_type;
 	viodev->dev.release = vio_dev_release;

@@ -1499,7 +1496,7 @@ static int __init vio_bus_init(void)
 	 * The fake parent of all vio devices, just to give us
 	 * a nice directory
 	 */
-	err = device_register(&vio_bus_device.dev);
+	err = device_register(&vio_bus);
 	if (err) {
 		printk(KERN_WARNING "%s: device_register returned %i\n",
 				__func__, err);
-- 
2.20.1