linux-kernel - Re: [PATCH RFC] staging: r8188eu: Use usb_control_msg_recv/send() in usbctrl

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Date:   Mon, 23 Aug 2021 11:30:53 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "open list:STAGING SUBSYSTEM" <linux-staging@...ts.linux.dev>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] staging: r8188eu: Use usb_control_msg_recv/send() in
 usbctrl_vendorreq()

On 8/23/21 11:11 AM, Pavel Skripkin wrote:
> On 8/23/21 2:02 AM, Fabio M. De Francesco wrote:
>> Replace usb_control_msg() with the new usb_control_msg_recv() and
>> usb_control_msg_send() API of USB Core.
>> 
>> This patch is an RFC for different reasons:
>> 
>> 1) I'm not sure if it is needed: while Greg Kroah-Hartman suggested to
>> use the new API in a message to a thread that was about a series of patches
>> submitted by Pavel Skripkin (who decided to not use it), I cannot explain
>> if and why the driver would benefit from this patch.
>> 2) I have doubts about the sematic of the API I use here, so I'd like to
>> know whether or not I'm using them properly.
>> 3) At the moment I cannot test the driver because I don't have my device
>> with me.
>> 4) This patch could probably lead to a slight change in some lines of
>> Pavel's series (for sure in usb_read*()).
>> 
>> I'd like to hear from the Maintainers and other interested people if this
>> patch is worth to be considered and, in this case, if there are suggestions
>> for the purpose to improve it.
>> 
>> Suggested-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
>> ---
>>   drivers/staging/r8188eu/hal/usb_ops_linux.c | 19 ++++++++++---------
>>   1 file changed, 10 insertions(+), 9 deletions(-)
>> 
>> diff --git a/drivers/staging/r8188eu/hal/usb_ops_linux.c b/drivers/staging/r8188eu/hal/usb_ops_linux.c
>> index 6a0a24acf292..9e290c1cc449 100644
>> --- a/drivers/staging/r8188eu/hal/usb_ops_linux.c
>> +++ b/drivers/staging/r8188eu/hal/usb_ops_linux.c
>> @@ -15,7 +15,7 @@ static int usbctrl_vendorreq(struct intf_hdl *pintfhdl, u16 value, void *pdata,
>>   	struct adapter	*adapt = pintfhdl->padapter;
>>   	struct dvobj_priv  *dvobjpriv = adapter_to_dvobj(adapt);
>>   	struct usb_device *udev = dvobjpriv->pusbdev;
>> -	unsigned int pipe;
>> +	u8 pipe;
>>   	int status = 0;
>>   	u8 reqtype;
> 
> I think, we can pass REALTEK_USB_VENQT_{READ,WRITE} directly as
> requesttype argument and get rid of u8 reqtype. + we can define these
> macros:
> 
> #define
> usbctrl_vendor_read(...)   usbctrl_vendorreq(...,REALTEK_USB_VENQT_READ)
> 
> 
> #define
> usbctrl_vendor_write()    usbctrl_vendorreq(...,REALTEK_USB_VENQT_WRITE)
> 
> 
> This will make code more nice, IMO  :)
> 
> 
> (Sorry for this formatting, my email client disabled "paste without
> formatting" option)
> 
>>   	u8 *pIo_buf;
>> @@ -47,19 +47,20 @@ static int usbctrl_vendorreq(struct intf_hdl *pintfhdl, u16 value, void *pdata,
>>   		memset(pIo_buf, 0, len);
>>   

		^^^^^^^^^^^^^^^^^^^^^^^

And this memset becomes useless, since usb_control_msg_recv cannot 
receive only part of the message

>>   		if (requesttype == 0x01) {
>> -			pipe = usb_rcvctrlpipe(udev, 0);/* read_in */
>>   			reqtype =  REALTEK_USB_VENQT_READ;
>> +			status = usb_control_msg_recv(udev, pipe, REALTEK_USB_VENQT_CMD_REQ,
>> +						      reqtype, value, REALTEK_USB_VENQT_CMD_IDX,
>> +						      pIo_buf, len, RTW_USB_CONTROL_MSG_TIMEOUT,
>> +						      GFP_KERNEL);
>>   		} else {
>> -			pipe = usb_sndctrlpipe(udev, 0);/* write_out */
>>   			reqtype =  REALTEK_USB_VENQT_WRITE;
>> -			memcpy(pIo_buf, pdata, len);
> 
> I guess, this memcpy is needed, since we want to send data from pdata
> 
> 
>> +			status = usb_control_msg_send(udev, pipe, REALTEK_USB_VENQT_CMD_REQ,
>> +						      reqtype, value, REALTEK_USB_VENQT_CMD_IDX,
>> +						      pIo_buf, len, RTW_USB_CONTROL_MSG_TIMEOUT,
>> +						      GFP_KERNEL);
>>   		}
>>   
>> -		status = usb_control_msg(udev, pipe, REALTEK_USB_VENQT_CMD_REQ,
>> -					 reqtype, value, REALTEK_USB_VENQT_CMD_IDX,
>> -					 pIo_buf, len, RTW_USB_CONTROL_MSG_TIMEOUT);
>> -
>> -		if (status == len) {   /*  Success this control transfer. */
>> +		if (!status) {   /*  Success this control transfer. */
>>   			rtw_reset_continual_urb_error(dvobjpriv);
>>   			if (requesttype == 0x01)
>>   				memcpy(pdata, pIo_buf,  len);
>> 
> 


With regards,
Pavel Skripkin