Re: [Linux-kernel-mentees] [PATCH 4/4] net: rndis_host: use usb_control_msg_recv() and usb_control_msg_send()

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Sep 23, 2020 at 02:35:19PM +0530, Himadri Pandya wrote:
> The new usb_control_msg_recv() and usb_control_msg_send() nicely wraps
> usb_control_msg() with proper error check. Hence use the wrappers
> instead of calling usb_control_msg() directly.
> 
> Signed-off-by: Himadri Pandya <himadrispandya@gmail.com>
> ---
>  drivers/net/usb/rndis_host.c | 44 ++++++++++++++----------------------
>  1 file changed, 17 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/net/usb/rndis_host.c b/drivers/net/usb/rndis_host.c
> index 6fa7a009a24a..30fc4a7183d3 100644
> --- a/drivers/net/usb/rndis_host.c
> +++ b/drivers/net/usb/rndis_host.c
> @@ -113,14 +113,13 @@ int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf, int buflen)
>  		buf->request_id = (__force __le32) xid;
>  	}
>  	master_ifnum = info->control->cur_altsetting->desc.bInterfaceNumber;
> -	retval = usb_control_msg(dev->udev,
> -		usb_sndctrlpipe(dev->udev, 0),
> -		USB_CDC_SEND_ENCAPSULATED_COMMAND,
> -		USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> -		0, master_ifnum,
> -		buf, le32_to_cpu(buf->msg_len),
> -		RNDIS_CONTROL_TIMEOUT_MS);
> -	if (unlikely(retval < 0 || xid == 0))
> +	retval = usb_control_msg_send(dev->udev, 0,
> +				      USB_CDC_SEND_ENCAPSULATED_COMMAND,
> +				      USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> +				      0, master_ifnum, buf,
> +				      le32_to_cpu(buf->msg_len),
> +				      RNDIS_CONTROL_TIMEOUT_MS);
> +	if (unlikely(xid == 0))
>  		return retval;
>  
>  	/* Some devices don't respond on the control channel until
> @@ -139,14 +138,11 @@ int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf, int buflen)
>  	/* Poll the control channel; the request probably completed immediately */
>  	rsp = le32_to_cpu(buf->msg_type) | RNDIS_MSG_COMPLETION;
>  	for (count = 0; count < 10; count++) {
> -		memset(buf, 0, CONTROL_BUFFER_SIZE);
> -		retval = usb_control_msg(dev->udev,
> -			usb_rcvctrlpipe(dev->udev, 0),
> -			USB_CDC_GET_ENCAPSULATED_RESPONSE,
> -			USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> -			0, master_ifnum,
> -			buf, buflen,
> -			RNDIS_CONTROL_TIMEOUT_MS);
> +		retval = usb_control_msg_recv(dev->udev, 0,
> +					      USB_CDC_GET_ENCAPSULATED_RESPONSE,
> +					      USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> +					      0, master_ifnum, buf, buflen,
> +					      RNDIS_CONTROL_TIMEOUT_MS);
>  		if (likely(retval >= 8)) {

retval here is never going to be positive, right?  So I don't think this
patch is correct :(

>  			msg_type = le32_to_cpu(buf->msg_type);
>  			msg_len = le32_to_cpu(buf->msg_len);
> @@ -178,17 +174,11 @@ int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf, int buflen)
>  				msg->msg_type = cpu_to_le32(RNDIS_MSG_KEEPALIVE_C);
>  				msg->msg_len = cpu_to_le32(sizeof *msg);
>  				msg->status = cpu_to_le32(RNDIS_STATUS_SUCCESS);
> -				retval = usb_control_msg(dev->udev,
> -					usb_sndctrlpipe(dev->udev, 0),
> -					USB_CDC_SEND_ENCAPSULATED_COMMAND,
> -					USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> -					0, master_ifnum,
> -					msg, sizeof *msg,
> -					RNDIS_CONTROL_TIMEOUT_MS);
> -				if (unlikely(retval < 0))
> -					dev_dbg(&info->control->dev,
> -						"rndis keepalive err %d\n",
> -						retval);
> +				retval = usb_control_msg_send(dev->udev, 0,
> +							      USB_CDC_SEND_ENCAPSULATED_COMMAND,
> +							      USB_TYPE_CLASS | USB_RECIP_INTERFACE,
> +							      0, master_ifnum, msg, sizeof(*msg),
> +							      RNDIS_CONTROL_TIMEOUT_MS);

You lost the error message that the previous call had if something went
wrong.  Don't know if it's really needed, but there's no reason to
remove it here.

thanks,

greg k-h
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