https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=298838
Bug ID: 298838
Summary: umb(4): expose MBIM software radio state/control to
userland
Product: Base System
Version: 15.1-RELEASE
Hardware: Any
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: kern
Assignee: [email protected]
Reporter: [email protected]
umb(4) already implements MBIM software-radio control and records hardware and
software radio state, but userland cannot access either. At present, the only
tested way to ensure that the modem is no longer active is to power off the USB
device. If exposing these functions to userland is desirable, the remaining
question is which FreeBSD interface should provide them.
---
Environment
-----------
FreeBSD 15.1-RELEASE-p2 amd64
Modem:
Dell DW5811e Snapdragon X7 LTE
Sierra Wireless EM7455B
Driver:
umb(4)
Control utility:
umbctl(8)
Existing kernel support
-----------------------
umb(4) implements radio control through MBIM_CID_RADIO_STATE.
The driver provides:
umb_radio()
which sends:
MBIM_RADIO_STATE_ON
MBIM_RADIO_STATE_OFF
The driver also records:
hw_radio_on
sw_radio_on
Neither radio control nor these state values is available through umbctl(8).
Current umbctl(8) interface
---------------------------
umbctl(8) provides configuration for:
APN
username
password
PIN / PUK
roaming
It does not provide:
software radio on/off
hardware radio state
software radio state
Observed shutdown behavior
--------------------------
Starting with umb0 connected:
ifconfig umb0 down
disconnects the data session while the modem remains attached.
A subsequent:
ifconfig umb0 down
attempts packet-service detach. The modem returns:
MBIM_CID_PACKET_SERVICE failed: FAILURE
The relevant umb(4) shutdown sequence is:
disconnect
packet-service detach
radio off
Because packet-service detach fails, the driver does not reach the radio-off
step on this modem.
The resulting state is:
data session disconnected
packet service attached
software radio on
Current workaround
------------------
The only tested method that ensures the modem is no longer active is powering
off the USB device.
This removes the modem from the system.
After a USB power cycle, the modem has also enumerated at High Speed instead of
SuperSpeed. A reboot was required to restore SuperSpeed operation.
USB power control is therefore not suitable as the normal radio-control
mechanism.
Addressed capability
--------------------
Should userland have access to the radio control already implemented in umb(4)?
The operations needed here are:
radio off
radio on
report hardware radio state
report software radio state
One possible umbctl(8) interface would be:
umbctl umb0 radio off
umbctl umb0 radio on
The command syntax is not the issue.
The question is which FreeBSD interface should provide this functionality if
radio control and radio-state reporting are intended to be available to
userland.
Questions
---------
1. Is the absence of userland MBIM radio control intentional?
2. If not, which FreeBSD interface should provide access to the existing umb(4)
radio-control operation?
3. Should the hardware and software radio states also be available to userland?
4. Should this functionality belong in umbctl(8), ifconfig(8), or another
interface?
I can test patches on this modem.
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