Hello.
How to correctly turn off the port power of usb hub (assuming hub
supports individual port power switching). Correctly means that all
drivers using the device on that port are notified before the power is
removed. Removed device could also be a usb hub.
My experiments with function
usb_control_msg(
hdev, usb_sndctrlpipe(hdev, 0),
USB_REQ_CLEAR_FEATURE,
USB_RT_PORT,
USB_PORT_FEAT_POWER,
port1,
NULL, 0, 1000);
will not give desired results.
When I try to turn off port power with usb_control_msg, the port resides
on usb hub (not root hub), then the power is indeed switched off but
drivers are not notified. The devices I use are usb 1.1 and 2.0 mass
storage devices, linux kernel 2.6.18. After the feat power feature was
cleared the power went away for a couple of seconds but then (i think
this was the scsi subsystem who wanted to perform IO with the device)
usb subsystem found logical disconnect on port and the device was
re-powered... Things get more complicated if port power must be switched
off on root hub that has kind of controller where each port is shared by
ohci - ehci driver. Most 2.0 pci to usb root hubs fall to that category.
If the port is used by both drivers (actually the sharing starts from
hardware) then the power must be turned off (port power feature cleared)
on both controllers. I don't know the generic solution how to set up
port mapping, except looking to the datasheet.
My question is how can I notify all drivers related to given usb hub
port when i have (struct usb_device *dev)
where dev is the device on hub port where the power must be switched off?
JR
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