From: Greg KH <greg@kroah.com>
To: Lucas Tanure <tanure@linux.com>
Cc: linux-usb@vger.kernel.org, kernelnewbies@kernelnewbies.org
Subject: Re: USB Question about devices being reconnected to the host
Date: Thu, 15 Oct 2020 14:30:56 +0200 [thread overview]
Message-ID: <20201015123056.GA4021854@kroah.com> (raw)
In-Reply-To: <d4c94e87-a1bb-18d5-054f-2e6ed01fab5b@linux.com>
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
next prev parent reply other threads:[~2020-10-15 12:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-15 12:17 USB Question about devices being reconnected to the host Lucas Tanure
2020-10-15 12:30 ` Greg KH [this message]
2020-10-15 13:22 ` Lucas Tanure
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