linux-kernel - Re: [PATCH 04/26] usb: gadget: introduce 'enabled' flag in struct usb

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Message-id: <55F83B37.20408@samsung.com>
Date:	Tue, 15 Sep 2015 17:37:27 +0200
From:	Krzysztof Opasiak <k.opasiak@...sung.com>
To:	Robert Baldyga <r.baldyga@...sung.com>, balbi@...com
Cc:	gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, b.zolnierkie@...sung.com,
	m.szyprowski@...sung.com, andrzej.p@...sung.com
Subject: Re: [PATCH 04/26] usb: gadget: introduce 'enabled' flag in struct
 usb_ep

Hello,

On 09/15/2015 04:26 PM, Robert Baldyga wrote:
> This patch introduces 'enabled' flag in struct usb_ep, and modifies
> usb_ep_enable() and usb_ep_disable() functions to encapsulate endpoint
> enabled/disabled state. It helps to avoid enabling endpoints which are
> already enabled, and disabling endpoints which are already disables.
>
>>>From now USB functions don't have to remember current endpoint
> enable/disable state, as this state is now handled automatically which
> makes this API less bug-prone.
>
> Signed-off-by: Robert Baldyga <r.baldyga@...sung.com>
> ---
>   include/linux/usb/gadget.h | 21 +++++++++++++++++++--
>   1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index 3f299e2..63375cd 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -215,6 +215,7 @@ struct usb_ep {
>   	struct list_head	ep_list;
>   	struct usb_ep_caps	caps;
>   	bool			claimed;
> +	bool			enabled;
>   	unsigned		maxpacket:16;
>   	unsigned		maxpacket_limit:16;
>   	unsigned		max_streams:16;
> @@ -264,7 +265,15 @@ static inline void usb_ep_set_maxpacket_limit(struct usb_ep *ep,
>    */
>   static inline int usb_ep_enable(struct usb_ep *ep)
>   {
> -	return ep->ops->enable(ep, ep->desc);
> +	int ret = 0;
> +
> +	if (!ep->enabled) {
> +		ret = ep->ops->enable(ep, ep->desc);
> +		if (!ret)
> +			ep->enabled = true;
> +	}
> +
> +	return ret;
>   }
>
>   /**
> @@ -281,7 +290,15 @@ static inline int usb_ep_enable(struct usb_ep *ep)
>    */
>   static inline int usb_ep_disable(struct usb_ep *ep)
>   {
> -	return ep->ops->disable(ep);
> +	int ret = 0;
> +
> +	if (ep->enabled) {
> +		ret = ep->ops->disable(ep);
> +		if (!ret)
> +			ep->enabled = false;
> +	}
> +
> +	return ret;
>   }
>

Personally I don't like this convention. In my opinion usb_ep_disable() 
& usb_ep_enable() should fail if ep is already disabled/enabled. Then in 
function code we should check if endpoint is enabled (maybe even we 
should have usb_ep_is_enabled()) and call disable only when it is really 
enabled.

Best Regards,
-- 
Krzysztof Opasiak
Samsung R&D Institute Poland
Samsung Electronics
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