On 01/06/2014 22:35, Alex J Lennon wrote: > > On 01/06/2014 22:22, Alexandru Vaduva wrote: >> This are indeed some very good news Alex J Lennon. >> I have some questions, but those maybe can be answered by the >> maintainers of the meta-raspberrypi layer: >> Why was this change done? >> -PREFERRED_PROVIDER_virtual/egl ?= "vc-graphics-hardfp" >> -PREFERRED_PROVIDER_virtual/libgles2 ?= "vc-graphics-hardfp" >> +PREFERRED_PROVIDER_virtual/egl ?= "userland" >> +PREFERRED_PROVIDER_virtual/libgles2 ?= "userland" >> How it may affect other applications? >> Andrei: Do you have any input on this? >> >>
I think I've worked out what is happening. It looks like an interesting, and pretty obscure, effect of the default bitbake linker flags. There's an __attribute__(constructor) decorated function that is supposed to be executed when libmmal_vc_client.so is loaded. However by default bitbake passes in LDFLAGS of --as-needed which means that although raspivid is set to be linked against libmmal_vc_client, the dependency, which is un-needed by raspivid as there's no call into that library, is removed. The userland code for Raspivid tries to create a component with a call to mmal_component_create() which is in libmmal_core ref: https://github.com/raspberrypi/userland/blob/master/host_applications/linux/apps/raspicam/RaspiVid.c This function goes to a default constructor which walks a list mmal_component_supplier_create(const char *name, MMAL_COMPONENT_T *component) ref: https://github.com/raspberrypi/userland/blob/master/interface/mmal/core/mmal_component.c The function that populates the supplier list, mmal_component_supplier_register(), is called from a function in another library, libmmal_vc_client, which is decorated with MMAL_CONSTRUCTOR(mmal_register_component_videocore); which is defined as # define MMAL_CONSTRUCTOR(func) void __attribute__((constructor,used)) func(void) i.e. This registration function would normally execute when the library it lives in is loaded, but because there's no call into that library from raspivid, and because we linked with --as-needed, the library is removed from the executable's dependency list, and the components are never registered... Diffing the working and non-working raspivids, Dynamic Section: NEEDED libmmal_core.so NEEDED libmmal_util.so - NEEDED libmmal_vc_client.so NEEDED libvcos.so So if I modify the userland_git.bb to remove the --as-needed +LDFLAGS="-Wl,-O1 -Wl,--hash-style=gnu" With this change I can now build userland out of meta-raspberrypi and raspivid works for me. Cheers, Alex
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