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* USB Question about devices being reconnected to the host
@ 2020-10-15 12:17 Lucas Tanure
  2020-10-15 12:30 ` Greg KH
  0 siblings, 1 reply; 3+ messages in thread
From: Lucas Tanure @ 2020-10-15 12:17 UTC (permalink / raw)
  To: linux-usb, kernelnewbies

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.

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

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?

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

Driver:

#define DEBUG
#include <linux/of.h>
#include <linux/usb.h>
#include <linux/module.h>

static int usbdev_probe(struct usb_interface *intf, const struct 
usb_device_id *id)
{
	pr_info("%s", __func__);

	return 0;
}

static void usbdev_disconnect(struct usb_interface *intf)
{
	pr_info("%s", __func__);
}

static int usbdev_suspend(struct usb_interface *intf, pm_message_t message)
{
	pr_err("%s", __func__);
	return 0;
}

static int usbdev_resume(struct usb_interface *intf)
{
	pr_info("%s", __func__);
	return 0;
}

static int usbdev_reset_resume(struct usb_interface *intf)
{
	pr_info("%s", __func__);
	return 0;
}

static int usbdev_pre_reset(struct usb_interface *intf)
{
	pr_info("%s", __func__);
	return 0;
}

static int usbdev_post_reset(struct usb_interface *intf)
{
	pr_info("%s", __func__);
	return 0;
}

static const struct usb_device_id usbdev_id_table[] = {
	{ USB_DEVICE(0x04b4, 0x00f1) },
	{}
};
MODULE_DEVICE_TABLE(usb, usbdev_id_table);

static struct usb_driver usbdev_driver = {
	.name			= "My USB Device",
	.probe			= usbdev_probe,
	.disconnect		= usbdev_disconnect,
	.id_table		= usbdev_id_table,
	.suspend	 	= usbdev_suspend,
	.resume			= usbdev_resume,
	.reset_resume 	= usbdev_reset_resume,
	.pre_reset		= usbdev_pre_reset,
	.post_reset 	= usbdev_post_reset,
};

module_usb_driver(usbdev_driver);

MODULE_AUTHOR("Lucas Tanure <tanure@linux.com>");
MODULE_DESCRIPTION("Driver for My USB device");
MODULE_LICENSE("GPL v2");

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^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: USB Question about devices being reconnected to the host
  2020-10-15 12:17 USB Question about devices being reconnected to the host Lucas Tanure
@ 2020-10-15 12:30 ` Greg KH
  2020-10-15 13:22   ` Lucas Tanure
  0 siblings, 1 reply; 3+ messages in thread
From: Greg KH @ 2020-10-15 12:30 UTC (permalink / raw)
  To: Lucas Tanure; +Cc: linux-usb, kernelnewbies

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

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^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: USB Question about devices being reconnected to the host
  2020-10-15 12:30 ` Greg KH
@ 2020-10-15 13:22   ` Lucas Tanure
  0 siblings, 0 replies; 3+ messages in thread
From: Lucas Tanure @ 2020-10-15 13:22 UTC (permalink / raw)
  To: Greg KH; +Cc: linux-usb, kernelnewbies



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
> 

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Kernelnewbies mailing list
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^ permalink raw reply	[flat|nested] 3+ messages in thread

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2020-10-15 12:17 USB Question about devices being reconnected to the host Lucas Tanure
2020-10-15 12:30 ` Greg KH
2020-10-15 13:22   ` Lucas Tanure

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