USB Question about devices being reconnected to the host

[Lucas Tanure]

On 10/15/20 1:30 PM, Greg KH wrote:
> 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?
I re-did the test couple more times and I can see now the probe
function being called.

Thanks
> 
> 
>>
>> 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
>