Description
Either there are more revisions of DELL P2416D monitors with different internal hubs, or I have missed something, or this hub should be moved to errata section from the list of supported devices.
From my point of view uhubctl is able only to manage data lines, not the power ones. Despite the hub reports per-port power switching, I could not get a LED switched off even when uhubctl reported no power at the port. However I could "re-connect" a USB device after echo 1 >/sys/bus/usb/devices/.../remove using uhubctl -a off ...; uhubctl -a on ... commands.
Actually there is a way to turn off all ports through i2c bus but the screen is turned off as well
ddccontrol -r 0xd6 -w 5 dev:/dev/i2c-4 # off
ddccontrol -r 0xe1 -w 0 dev:/dev/i2c-4 # on
I am afraid, the author of #164 would not provide more details. In my case it is
- DELL P2416D
- Model: No P2416Db
- Made: week 3 of 2017
- Model in EDID: DELA0C2, DELA0C3
- 4-ports USB 2.0 HUB
0424:2514(notice that newer models of DELL monitors have USB 3 hubs)
Bus 002 Device 057: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
lsusb -v -d 0424:2514
Bus 002 Device 057: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 9 Hub
bDeviceSubClass 0 Unused
bDeviceProtocol 2 TT per port
bMaxPacketSize0 64
idVendor 0x0424 Standard Microsystems Corp.
idProduct 0x2514 USB 2.0 Hub
bcdDevice b.b3
iManufacturer 0
iProduct 0
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 41
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xe0
Self Powered
Remote Wakeup
MaxPower 2mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 9 Hub
bInterfaceSubClass 0 Unused
bInterfaceProtocol 1 Single TT
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0001 1x 1 bytes
bInterval 12
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 1
bNumEndpoints 1
bInterfaceClass 9 Hub
bInterfaceSubClass 0 Unused
bInterfaceProtocol 2 TT per port
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0001 1x 1 bytes
bInterval 12
Hub Descriptor:
bLength 9
bDescriptorType 41
nNbrPorts 4
wHubCharacteristic 0x0009
Per-port power switching
Per-port overcurrent protection
TT think time 8 FS bits
bPwrOn2PwrGood 50 * 2 milli seconds
bHubContrCurrent 1 milli Ampere
DeviceRemovable 0x00
PortPwrCtrlMask 0xff
Hub Port Status:
Port 1: 0000.0100 power
Port 2: 0000.0100 power
Port 3: 0000.0100 power
Port 4: 0000.0100 power
Device Qualifier (for other device speed):
bLength 10
bDescriptorType 6
bcdUSB 2.00
bDeviceClass 9 Hub
bDeviceSubClass 0 Unused
bDeviceProtocol 0 Full speed (or root) hub
bMaxPacketSize0 64
bNumConfigurations 1
Device Status: 0x0001
Self Powered
Accordingly to README, only hubs that could turn off power lines are considered as supported, so at least a footnote should be added to the entry for DELL P2416D that at least some devices are only partially supported.
P.S.
An idea that could be discussed in a dedicated issue. Have you considered marking device as not authorized before turning the port off? It seems it could be more reliable than suggesting to perform multiple commands struggling with kernel attempts to restore device state. And it is not so severe as remove interface. An example for a mouse connected to the hub in P2416D:
# uhubctl -a off -l 2-2 -p 2
Current status for hub 2-2 [0424:2514]
Port 2: 0303 power lowspeed enable connect [09da:000a A4Tech USB Mouse]
Sent power off request
New status for hub 2-2 [0424:2514]
Port 2: 0000 off
# uhubctl -l 2-2 -p 2
Current status for hub 2-2 [0424:2514]
Port 2: 0303 power lowspeed enable connect [09da:000a A4Tech USB Mouse]
# echo 0 >/sys/bus/usb/devices/2-2.2/authorized
# uhubctl -a off -l 2-2 -p 2
Current status for hub 2-2 [0424:2514]
Port 2: 0303 power lowspeed enable connect [09da:000a A4Tech USB Mouse]
Sent power off request
New status for hub 2-2 [0424:2514]
Port 2: 0000 off
# uhubctl -l 2-2 -p 2
Current status for hub 2-2 [0424:2514]
Port 2: 0000 off
https://www.kernel.org/doc/html/latest/usb/authorization.html
Authorizing (or not) your USB devices to connect to the system