IB/mthca: Always build debugging code unless CONFIG_EMBEDDED=y

Change the mthca debugging trace output code so that it can enabled
and disabled at runtime with the debug_level module parameter in
sysfs. Also, don't allow CONFIG_INFINIBAND_MTHCA_DEBUG to be disabled
unless CONFIG_EMBEDDED is selected. We want users (and especially
distros) to have this turned on unless they really need to save space,
because by the time we want debugging output, it's usually too late to
rebuild a kernel.

Signed-off-by: Roland Dreier <[e-mail]>

drivers/infiniband/hw/mthca/Kconfig

···
 	  ("Tavor") and the MT25208 PCI Express HCA ("Arbel").
 
 config INFINIBAND_MTHCA_DEBUG
-	bool "Verbose debugging output"
+	bool "Verbose debugging output" if EMBEDDED
 	depends on INFINIBAND_MTHCA
-	default n
+	default y
 	---help---
-	  This option causes the mthca driver produce a bunch of debug
-	  messages.  Select this is you are developing the driver or
-	  trying to diagnose a problem.
+	  This option causes debugging code to be compiled into the
+	  mthca driver.  The output can be turned on via the
+	  debug_level module parameter (which can also be set after
+	  the driver is loaded through sysfs).

drivers/infiniband/hw/mthca/Makefile

···
-ifdef CONFIG_INFINIBAND_MTHCA_DEBUG
-EXTRA_CFLAGS += -DDEBUG
-endif
-
 obj-$(CONFIG_INFINIBAND_MTHCA) += ib_mthca.o
 
 ib_mthca-y :=	mthca_main.o mthca_cmd.o mthca_profile.o mthca_reset.o \

drivers/infiniband/hw/mthca/mthca_dev.h

···
 	spinlock_t            sm_lock;
 };
 
-#define mthca_dbg(mdev, format, arg...) \
-	dev_dbg(&mdev->pdev->dev, format, ## arg)
+#ifdef CONFIG_INFINIBAND_MTHCA_DEBUG
+extern int mthca_debug_level;
+
+#define mthca_dbg(mdev, format, arg...)					\
+	do {								\
+		if (mthca_debug_level)					\
+			dev_printk(KERN_DEBUG, &mdev->pdev->dev, format, ## arg); \
+	} while (0)
+
+#else /* CONFIG_INFINIBAND_MTHCA_DEBUG */
+
+#define mthca_dbg(mdev, format, arg...) do { (void) mdev; } while (0)
+
+#endif /* CONFIG_INFINIBAND_MTHCA_DEBUG */
+
 #define mthca_err(mdev, format, arg...) \
 	dev_err(&mdev->pdev->dev, format, ## arg)
 #define mthca_info(mdev, format, arg...) \

drivers/infiniband/hw/mthca/mthca_main.c

···
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_VERSION(DRV_VERSION);
 
+#ifdef CONFIG_INFINIBAND_MTHCA_DEBUG
+
+int mthca_debug_level = 0;
+module_param_named(debug_level, mthca_debug_level, int, 0644);
+MODULE_PARM_DESC(debug_level, "Enable debug tracing if > 0");
+
+#endif /* CONFIG_INFINIBAND_MTHCA_DEBUG */
+
 #ifdef CONFIG_PCI_MSI
 
 static int msi_x = 0;