Re: [PATCH v2 06/10] export: allow definition default namespaces in Makefiles or sources

[Greg KH]

On Tue, Aug 13, 2019 at 01:17:03PM +0100, Matthias Maennich wrote:
> 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

I thought we were trying to get away from cflags :(

> 
> 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.

Ok, good, hopefully the cflags stuff will not be the default for people.

thanks,

greg k-h