linux-kernel - [RFC 02/10] fusbh200: Make Xen notificaiton consistent with EHCI

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Message-Id: <1410286296-5109-3-git-send-email-chris@rorvick.com>
Date:	Tue,  9 Sep 2014 13:11:28 -0500
From:	Chris Rorvick <chris@...vick.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Chris Rorvick <chris@...vick.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oneukum@...e.de>, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: [RFC 02/10] fusbh200: Make Xen notificaiton consistent with EHCI

If CONFIG_XEN_DOM0 is enabled, the ehci-dbgp driver notifies Xen of
controller reset events via xen_dbgp_reset_prep() and
xen_dbgp_external_startup() (via calls to xen_dbgp_op().)  Otherwise
<linux/usb/ehci_def.h> defines them as no-ops to disable this logic.

The fusbh200 driver copies much of the dbgp code from ehci_def.h, but it
unconditionally defines the Xen hooks as no-ops, effectively disabling
these notifications when CONFIG_EARLY_PRINTK_DBGP is disabled.  When
enabled, though, notifying Xen is dependent on CONFIG_XEN_DOM0 due to
fusbh200 leveraging the ehci-dbgp driver.

The following table compares the implementations of xen_dbgp_reset_prep()
and xen_dbgp_external_startup() in the ehci-dbgp and fusbh200 drivers
under the relevant configurations:

  EARLY_PRINTK_DBGP?  XEN_DOM0?  ehci-dbgp      fusbh200
  ------------------  ---------  -------------  -------------
  n                   n          no-op          no-op
  n                   y          xen_dbgp_op()  no-op
  y                   n          no-op          no-op
  y                   y          xen_dbgp_op()  xen_dbgp_op()

This suggests that fusbh200 is, at best, indifferent to whether Xen is
notified of these events.  Make fusbh200 consistent with ehci-dbgp as a
step towards consolidating this code duplication.

Signed-off-by: Chris Rorvick <chris@...vick.com>
---
 drivers/usb/host/fusbh200.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/host/fusbh200.h b/drivers/usb/host/fusbh200.h
index 6b719e0..6e7b8c1 100644
--- a/drivers/usb/host/fusbh200.h
+++ b/drivers/usb/host/fusbh200.h
@@ -318,6 +318,10 @@ extern struct console early_dbgp_console;
 
 struct usb_hcd;
 
+#ifdef CONFIG_XEN_DOM0
+extern int xen_dbgp_reset_prep(struct usb_hcd *);
+extern int xen_dbgp_external_startup(struct usb_hcd *);
+#else
 static inline int xen_dbgp_reset_prep(struct usb_hcd *hcd)
 {
 	return 1; /* Shouldn't this be 0? */
@@ -327,6 +331,7 @@ static inline int xen_dbgp_external_startup(struct usb_hcd *hcd)
 {
 	return -1;
 }
+#endif
 
 #ifdef CONFIG_EARLY_PRINTK_DBGP
 /* Call backs from fusbh200 host driver to fusbh200 debug driver */
-- 
1.9.3

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