Subject: Re: [RFC 1/4] Add usb_get_address and usb_set_address support

From: Greg KH <[email-masked]>
Date: Tue, 20 Aug 2019 15:26:02 -0700

On Tue, Aug 20, 2019 at 10:18:42PM +0000, [email-masked] wrote:
> The core USB driver message.c is missing get/set address functionality
> that stops ifconfig from being able to push MAC addresses out to USB
> based ethernet devices.  Without this functionality, some USB devices
> stop responding to ethernet packets when using ifconfig to change MAC
> addresses.  This has been tested with a Dell Universal Dock D6000.
> 
> Signed-off-by: Charles Hyde <[email-masked]>
> Cc: Mario Limonciello <[email-masked]>
> Cc: Greg Kroah-Hartman <[email-masked]>
> Cc: [email-masked]
> ---
>  drivers/usb/core/message.c | 59 ++++++++++++++++++++++++++++++++++++++
>  include/linux/usb.h        |  3 ++
>  2 files changed, 62 insertions(+)
> 
> diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
> index 5adf489428aa..eea775234b09 100644
> --- a/drivers/usb/core/message.c
> +++ b/drivers/usb/core/message.c
> @@ -1085,6 +1085,65 @@ int usb_clear_halt(struct usb_device *dev, int pipe)
>  }
>  EXPORT_SYMBOL_GPL(usb_clear_halt);
>  
> +/**
> + * usb_get_address - 

trailing whitespace?

No description of what the function does?

> + * @dev: device whose endpoint is halted
> + * @mac: buffer for containing 

Trailing whitespace?

> + * Context: !in_interrupt ()
> + *
> + * This will attempt to get the six byte MAC address from a USB device's
> + * ethernet controller using GET_NET_ADDRESS command.
> + *
> + * This call is synchronous, and may not be used in an interrupt context.
> + *
> + * Return: Zero on success, or else the status code returned by the
> + * underlying usb_control_msg() call.
> + */
> +int usb_get_address(struct usb_device *dev, unsigned char * mac)
> +{
> +	int ret = -ENOMEM;
> +	unsigned char *tbuf = kmalloc(256, GFP_NOIO);
> +
> +	if (!tbuf)
> +		return -ENOMEM;
> +
> +	ret = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
> +			USB_CDC_GET_NET_ADDRESS,
> +			USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> +			0, USB_REQ_SET_ADDRESS, tbuf, 256,
> +			USB_CTRL_GET_TIMEOUT);
> +	if (ret == 6)
> +		memcpy(mac, tbuf, 6);
> +
> +	kfree(tbuf);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(usb_get_address);

This is a VERY cdc-net-specific function.  It is not a "generic" USB
function at all.  Why does it belong in the USB core?  Shouldn't it live
in the code that handles the other cdc-net-specific logic?

thanks,

greg k-h