linux-kernel - Re: [PATCH 1/2] drivers: usb: gadget: udc: add missing break in switch

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Date:   Wed, 08 Feb 2017 14:16:27 +0100
From:   Michal Nazarewicz <mina86@...a86.com>
To:     Felipe Balbi <balbi@...nel.org>,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        gregkh@...uxfoundation.org, bhumirks@...il.com
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] drivers: usb: gadget: udc: add missing break in switch

On Wed, Feb 08 2017, Felipe Balbi wrote:
> Hi,
>
> "Gustavo A. R. Silva" <garsilva@...eddedor.com> writes:
>> Add missing break in switch.
>>
>> Addresses-Coverity-ID: 201385
>> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
>> ---
>>  drivers/usb/gadget/udc/mv_udc_core.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/usb/gadget/udc/mv_udc_core.c b/drivers/usb/gadget/udc/mv_udc_core.c
>> index 27ebb0d..56b3574 100644
>> --- a/drivers/usb/gadget/udc/mv_udc_core.c
>> +++ b/drivers/usb/gadget/udc/mv_udc_core.c
>> @@ -489,6 +489,7 @@ static int mv_ep_enable(struct usb_ep *_ep,
>>  		break;
>>  	case USB_ENDPOINT_XFER_CONTROL:
>>  		ios = 1;
>> +		break;
>
> are you SURE this is supposed to have this break statement? What if we
> want to initialize mult to 0 *also* for control endpoints? How did you
> test this? Do you have access to Marvel's documentation for this
> controller?

Actually it doesn’t matter.  mult is initialised to zero when it’s
declared and then not touched before the switch.

To improve readability, maybe something like:

---- >8 ------------------------------------------------------------
diff --git a/drivers/usb/gadget/udc/mv_udc_core.c b/drivers/usb/gadget/udc/mv_udc_core.c
index d82a91bddbd9..7440c9f92ec1 100644
--- a/drivers/usb/gadget/udc/mv_udc_core.c
+++ b/drivers/usb/gadget/udc/mv_udc_core.c
@@ -445,7 +445,8 @@ static int mv_ep_enable(struct usb_ep *_ep,
        struct mv_dqh *dqh;
        u16 max = 0;
        u32 bit_pos, epctrlx, direction;
-       unsigned char zlt = 0, ios = 0, mult = 0;
+       const unsigned char zlt = 1;
+       unsigned char ios, mult;
        unsigned long flags;
 
        ep = container_of(_ep, struct mv_ep, ep);
@@ -465,8 +466,6 @@ static int mv_ep_enable(struct usb_ep *_ep,
         * disable HW zero length termination select
         * driver handles zero length packet through req->req.zero
         */
-       zlt = 1;
-
        bit_pos = 1 << ((direction == EP_DIR_OUT ? 0 : 16) + ep->ep_num);
 
        /* Check if the Endpoint is Primed */
@@ -481,16 +480,16 @@ static int mv_ep_enable(struct usb_ep *_ep,
                        (unsigned)bit_pos);
                goto en_done;
        }
+
        /* Set the max packet length, interrupt on Setup and Mult fields */
+       ios = 0;
+       mult = 0;
        switch (desc->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) {
        case USB_ENDPOINT_XFER_BULK:
-               zlt = 1;
-               mult = 0;
+       case USB_ENDPOINT_XFER_INT:
                break;
        case USB_ENDPOINT_XFER_CONTROL:
                ios = 1;
-       case USB_ENDPOINT_XFER_INT:
-               mult = 0;
                break;
        case USB_ENDPOINT_XFER_ISOC:
                /* Calculate transactions needed for high bandwidth iso */
---- >8 ------------------------------------------------------------


-- 
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»