bus: mhi: host: Only expose controller sysfs attributes on the controller device

The serial_number, oem_pk_hash and soc_reset attributes are registered through mhi_bus_type.dev_groups, so the driver core creates them for every device on the MHI bus. MHI client devices (the per-channel devices such as mhi0_DUN or mhi0_MBIM) are also MHI bus devices, so each of them ends up with its own copies of these files even though they all operate on the same mhi_controller:

  $ ls /sys/bus/mhi/devices/mhi0_DUN/
  driver  oem_pk_hash  power  serial_number  soc_reset  subsystem  uevent

This is wrong for several reasons:

- The attributes describe the controller, not the channel. Their callbacks all dereference mhi_dev->mhi_cntrl and read BHI registers or issue a controller-wide SoC reset, so writing soc_reset through mhi0_DUN resets the whole device while looking like a per-channel operation.
- oem_pk_hash reports failures with dev_err(dev, ...), so a single failing controller produces one log line per registered channel device instead of one.
- Userspace has no way to tell which copy is authoritative.

Move the attributes off the bus and attach them to the controller device only. mhi_register_controller() now installs the group via mhi_dev->dev.groups before device_add(), while the channel devices created by mhi_create_devices() are left untouched. No functional change for the controller device; the files stay at the paths listed in Documentation/ABI/stable/sysfs-bus-mhi.

Note that trigger_edl was already handled this way, through an explicit sysfs_create_file() on the controller kobject, which is why it never appeared on the channel devices.

---
 drivers/bus/mhi/host/init.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

index fd3050889412..b4b254d1c6b9 100644
@@ -150,13 +150,21 @@ static ssize_t trigger_edl_store(struct device *dev,
 }
 static DEVICE_ATTR_WO(trigger_edl);
 
-static struct attribute *mhi_dev_attrs[] = {
+static struct attribute *mhi_cntrl_dev_attrs[] = {
 	&dev_attr_serial_number.attr,
 	&dev_attr_oem_pk_hash.attr,
 	&dev_attr_soc_reset.attr,
 	NULL,
 };
-ATTRIBUTE_GROUPS(mhi_dev);
+
+static const struct attribute_group mhi_cntrl_dev_group = {
+	.attrs = mhi_cntrl_dev_attrs,
+};
+
+static const struct attribute_group *mhi_cntrl_dev_groups[] = {
+	&mhi_cntrl_dev_group,
+	NULL,
+};
 
 /* MHI protocol requires the transfer ring to be aligned with ring length */
 static int mhi_alloc_aligned_ring(struct mhi_controller *mhi_cntrl,

@@ -1019,6 +1027,8 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
 	dev_set_name(&mhi_dev->dev, "mhi%d", mhi_cntrl->index);
 	mhi_dev->name = dev_name(&mhi_dev->dev);
 
+	mhi_dev->dev.groups = mhi_cntrl_dev_groups;
+
 	/* Init wakeup source */
 	device_init_wakeup(&mhi_dev->dev, true);
 

@@ -1455,7 +1465,6 @@ const struct bus_type mhi_bus_type = {
 	.uevent = mhi_uevent,
 	.probe = mhi_probe,
 	.remove = mhi_remove,
-	.dev_groups = mhi_dev_groups,
 };
 
 static int __init mhi_init(void)

2.53.0