linux-kernel - Re: [PATCH 25/26] usb: gadget: dummy_hcd: replace usage of rc to check if a list element was found

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Message-ID: <YiT2odfvXhp4nsK4@kroah.com>
Date:   Sun, 6 Mar 2022 19:00:01 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jakob Koschel <jakobkoschel@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Felipe Balbi <balbi@...nel.org>, Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Cristian Birsan <cristian.birsan@...rochip.com>,
        Al Cooper <alcooperx@...il.com>, Li Yang <leoyang.li@....com>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Michal Simek <michal.simek@...inx.com>,
        "open list:USB GADGET/PERIPHERAL SUBSYSTEM" 
        <linux-usb@...r.kernel.org>, Mike Rapoport <rppt@...nel.org>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: Re: [PATCH 25/26] usb: gadget: dummy_hcd: replace usage of rc to
 check if a list element was found

On Sun, Mar 06, 2022 at 06:50:33PM +0100, Jakob Koschel wrote:
> To move the list iterator variable into the list_for_each_entry_*()
> macro in the future it should be avoided to use the list iterator
> variable after the loop body.
> 
> To *never* use the list iterator variable after the loop it was
> concluded to use a separate iterator variable [1].
> 
> This removes the need to check the rc value to determine if the
> break/goto was hit and can be made more obvious
> by checking if the variable was set within the list traversal loop.
> 
> Link: https://lore.kernel.org/all/YhdfEIwI4EdtHdym@kroah.com/
> Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
> ---
>  drivers/usb/gadget/udc/dummy_hcd.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
> index a2d956af42a2..f21944707707 100644
> --- a/drivers/usb/gadget/udc/dummy_hcd.c
> +++ b/drivers/usb/gadget/udc/dummy_hcd.c
> @@ -751,7 +751,7 @@ static int dummy_dequeue(struct usb_ep *_ep, struct usb_request *_req)
>  	struct dummy		*dum;
>  	int			retval = -EINVAL;
>  	unsigned long		flags;
> -	struct dummy_request	*req = NULL;
> +	struct dummy_request	*req = NULL, *tmp;
>  
>  	if (!_ep || !_req)
>  		return retval;
> @@ -763,17 +763,18 @@ static int dummy_dequeue(struct usb_ep *_ep, struct usb_request *_req)
>  
>  	local_irq_save(flags);
>  	spin_lock(&dum->lock);
> -	list_for_each_entry(req, &ep->queue, queue) {
> -		if (&req->req == _req) {
> -			list_del_init(&req->queue);
> +	list_for_each_entry(tmp, &ep->queue, queue) {
> +		if (&tmp->req == _req) {
> +			list_del_init(&tmp->queue);
>  			_req->status = -ECONNRESET;
> +			req = tmp;
>  			retval = 0;
>  			break;
>  		}
>  	}
>  	spin_unlock(&dum->lock);
>  
> -	if (retval == 0) {
> +	if (req) {

There's no need for this change as we are testing retval, not req here,
unlike the other udc drivers.

So this one I think is correct as-is, or am I mistaken somehow?

thanks,

greg k-h