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

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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@xxxxxxxxxxx>
---
  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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