USB Question about devices being reconnected to the host

[Greg KH]

On Thu, Oct 15, 2020 at 01:17:45PM +0100, Lucas Tanure wrote:
> Hi,
> 
> I'm learning about USB drivers and I would like to know about disconnecting
> and reconnecting usb devices.
> 
> I can see my probe function being called and also the disconnect function.
> But if I reconnect the device there is no call from the kernel to notify my
> driver about the device being reconnected.

That's not good, your driver should be told this.

> I can also see that the module for my driver was not unloaded, so I dont
> understand the life cycle of a USB device.

Modules are never auto-unloaded.

> If the module is not unloaded at disconnection and re-loaded for a new
> device being connected, how can the driver know the device is there after a
> disconnection?

The probe function should be called, are you sure it isn't?


> 
> Thanks
> Lucas
> 
> This is my dmesg for the driver at the end of this email:
> 
> [   34.706041] usb 1-1.1.2: new high-speed USB device number 5 using dwc_otg
> [   34.837647] usb 1-1.1.2: New USB device found, idVendor=04b4,
> idProduct=00f1, bcdDevice= 0.00
> [   34.837666] usb 1-1.1.2: New USB device strings: Mfr=1, Product=2,
> SerialNumber=0
> [   34.837679] usb 1-1.1.2: Product: FX3
> [   34.837693] usb 1-1.1.2: Manufacturer: Cypress
> [   34.902480] usbdev_probe
> [   34.902681] usbcore: registered new interface driver My USB Device
> [   45.416310] usb 1-1.1.2: USB disconnect, device number 5
> [   45.416655] usbdev_disconnect
> [   61.326035] usb 1-1.1.2: new high-speed USB device number 6 using dwc_otg
> [   61.457674] usb 1-1.1.2: New USB device found, idVendor=04b4,
> idProduct=00f1, bcdDevice= 0.00
> [   61.457692] usb 1-1.1.2: New USB device strings: Mfr=1, Product=2,
> SerialNumber=0
> [   61.457706] usb 1-1.1.2: Product: FX3
> [   61.457720] usb 1-1.1.2: Manufacturer: Cypress

That is odd, sorry, don't know what to suggest.

greg k-h