tjh.dev
export: allow definition default namespaces in Makefiles or sources
To avoid excessive usage of EXPORT_SYMBOL_NS(sym, MY_NAMESPACE), where
MY_NAMESPACE will always be the namespace we are exporting to, allow
exporting all definitions of EXPORT_SYMBOL() and friends by defining
DEFAULT_SYMBOL_NAMESPACE.
For example, to export all symbols defined in usb-common into the
namespace USB_COMMON, add a line like this to drivers/usb/common/Makefile:
ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=USB_COMMON
That is equivalent to changing all EXPORT_SYMBOL(sym) definitions to
EXPORT_SYMBOL_NS(sym, USB_COMMON). Subsequently all symbol namespaces
functionality will apply.
Another way of making use of this feature is to define the namespace
within source or header files similar to how TRACE_SYSTEM defines are
used:
#undef DEFAULT_SYMBOL_NAMESPACE
#define DEFAULT_SYMBOL_NAMESPACE USB_COMMON
Please note that, as opposed to TRACE_SYSTEM, DEFAULT_SYMBOL_NAMESPACE
has to be defined before including include/linux/export.h.
If DEFAULT_SYMBOL_NAMESPACE is defined, a symbol can still be exported
to another namespace by using EXPORT_SYMBOL_NS() and friends with
explicitly specifying the namespace.
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Martijn Coenen <maco@android.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
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