linux-kernel - Re: [PATCH 1/2] staging: r8188eu: Use usb_control_msg_recv/send() in usbctrl

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Date:   Tue, 24 Aug 2021 14:07:46 +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>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] staging: r8188eu: Use usb_control_msg_recv/send() in
 usbctrl_vendorreq()

On 8/24/21 11:53 AM, Fabio M. De Francesco wrote:
> On Tuesday, August 24, 2021 10:13:46 AM CEST Pavel Skripkin wrote:
>> On 8/24/21 1:37 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 in usbctrl_vendorreq().
>> > 
>> > Suggested-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
>> > ---
>> > 
>> > Thanks to Pavel Skripkin <paskripkin@...il.com> for his review of the
>> > RFC patch.
>> >   
>> > drivers/staging/r8188eu/hal/usb_ops_linux.c | 25 ++++++++++-----------
>> > 1 file changed, 12 insertions(+), 13 deletions(-)
>> > 
>> > [...]
>> >
>> Hi, Fabio!
>> 
>> Christophe is right about semantic part. 
> 
> Hi Pavel,
> 
> I haven't yet read Christophe's message (but I'm going to do it ASAP).
> I hope he found out what is wrong with the code, what made Phil's tests
> fail.
> 
>> Also,
>> 
>> if (!status) {
>> 
>> } else {
>> 	if (status < 0) {		<-
>> 					  |
>> 	} else {			  |
>> 					  |
>> 	}				<-
>> }					
>> 
>> Extra if-else is not needed, since status can be 0 and < 0, there is no 
>> 3rd state, like it was before.
> 
> Correct, thanks!
> 
> Now I read the following from the documentation of the new API...
> 
> "Return: If successful, 0 is returned, Otherwise, a negative error number."
> 
> I'll remove that status < 0 check and whatever else is no more necessary.
> Thanks, again :)
> 
> Regards,
> 

Btw, not related to your patch, but I start think, that this check:


	if (!pIo_buf) {
		DBG_88E("[%s] pIo_buf == NULL\n", __func__);
		status = -ENOMEM;
		goto release_mutex;
	}

Should be wrapped as

	if (WARN_ON(unlikely(!pIo_buf)) {
		...
	}

Since usb_vendor_req_buf is initialized in ->probe() and I can't see 
possible calltrace, which can cause zeroing this pointer.

Something _completely_ wrong is going on if usb_vendor_req_buf is NULL, 
and we should complain loud about it. What do you think?


With regards,
Pavel Skripkin