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[PATCH v2 2/6] vfio: platform: reset: add vfio_platform_reset_private.h

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  [PATCH v2 2/6] vfio: platform: reset: add vfio_platform_reset_private.h Eric Auger <eric.auger@linaro.org> - 2015-10-22 11:50 +0200
    Re: [PATCH v2 2/6] vfio: platform: reset: add vfio_platform_reset_private.h Arnd Bergmann <arnd@arndb.de> - 2015-10-22 12:20 +0200

#1253673 — [PATCH v2 2/6] vfio: platform: reset: add vfio_platform_reset_private.h

This header is to be included in all vfio reset modules. It
defines the module_vfio_reset_handler macro whose role is
- to define a module alias
- implement module init/exit function which respectively registers
  and unregisters the reset function.

Signed-off-by: Eric Auger <eric.auger@linaro.org>

---

v2: creation
- this defines the module_vfio_reset_handler macro as suggested by Arnd

Although Arnd suggested me to remove the vfio_platform_register_reset
symbol_get (since the module manager can handle the case where the
vfio-platform driver is not loaded), I prefered to keep it while
introducing the macro. The rationale is, when using symbol_get/put
we are able to release the hold from the reset module on vfio-platform
as soon as the registration is complete and I think this makes sense.
---
 drivers/vfio/platform/reset/Makefile               |  2 +-
 .../platform/reset/vfio_platform_reset_private.h   | 66 ++++++++++++++++++++++
 2 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 drivers/vfio/platform/reset/vfio_platform_reset_private.h

diff --git a/drivers/vfio/platform/reset/Makefile b/drivers/vfio/platform/reset/Makefile
index 2a486af..154a7d5 100644
--- a/drivers/vfio/platform/reset/Makefile
+++ b/drivers/vfio/platform/reset/Makefile
@@ -1,5 +1,5 @@
 vfio-platform-calxedaxgmac-y := vfio_platform_calxedaxgmac.o
 
-ccflags-y += -Idrivers/vfio/platform
+ccflags-y += -Idrivers/vfio/platform -Idrivers/vfio/platform/reset
 
 obj-$(CONFIG_VFIO_PLATFORM_CALXEDAXGMAC_RESET) += vfio-platform-calxedaxgmac.o
diff --git a/drivers/vfio/platform/reset/vfio_platform_reset_private.h b/drivers/vfio/platform/reset/vfio_platform_reset_private.h
new file mode 100644
index 0000000..f212a61
--- /dev/null
+++ b/drivers/vfio/platform/reset/vfio_platform_reset_private.h
@@ -0,0 +1,66 @@
+/*
+ * Interface used by VFIO platform reset modules to register/unregister
+ * their reset function
+ *
+ * Copyright (c) 2015 Linaro Ltd.
+ *              www.linaro.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef VFIO_PLATFORM_RESET_PRIVATE_H
+#define VFIO_PLATFORM_RESET_PRIVATE_H
+
+#include <linux/module.h>
+#include "vfio_platform_private.h"
+
+static int reset_module_register(struct module *module,
+				    const char *compat,
+				    vfio_platform_reset_fn_t reset)
+{
+	int (*register_reset)(struct module *, const char*,
+				vfio_platform_reset_fn_t);
+	int ret;
+
+	register_reset = symbol_get(vfio_platform_register_reset);
+	if (!register_reset)
+		return -EINVAL;
+	ret = register_reset(module, compat, reset);
+	symbol_put(vfio_platform_register_reset);
+	return ret;
+}
+
+static void reset_module_unregister(const char *compat)
+{
+	int (*unregister_reset)(const char *);
+
+	unregister_reset = symbol_get(vfio_platform_unregister_reset);
+	if (!unregister_reset)
+		return;
+
+	unregister_reset(compat);
+
+	symbol_put(vfio_platform_unregister_reset);
+}
+
+#define module_vfio_reset_handler(compat, reset)			\
+MODULE_ALIAS("vfio-reset:" compat);					\
+static int __init reset ## _module_init(void)				\
+{									\
+	return reset_module_register(THIS_MODULE, compat, &reset);	\
+};									\
+static void __exit reset ## _module_exit(void)				\
+{                                                                       \
+	reset_module_unregister(compat);				\
+};									\
+module_init(reset ## _module_init);					\
+module_exit(reset ## _module_exit)
+
+#endif /* VFIO_PLATFORM_RESET_PRIVATE_H */
-- 
1.9.1

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#1253689

On Thursday 22 October 2015 11:41:58 Eric Auger wrote:
> v2: creation
> - this defines the module_vfio_reset_handler macro as suggested by Arnd
> 
> Although Arnd suggested me to remove the vfio_platform_register_reset
> symbol_get (since the module manager can handle the case where the
> vfio-platform driver is not loaded), I prefered to keep it while
> introducing the macro. The rationale is, when using symbol_get/put
> we are able to release the hold from the reset module on vfio-platform
> as soon as the registration is complete and I think this makes sense.

This makes it highly unusual. I can't think of a good reason to allow
unloading the vfio platform module while a reset module is registered,
that just causes a memory leak (or possibly a crash) when you do
unload the core module while it's used by a reset driver, it
prevents the reset module from getting loaded without loading the
vfio module first (because the autoloading doesn't work), and it
means we don't catch build errors in invalid configurations where you
have only the reset driver but not the vfio driver enabled.

	Arnd
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