On 28/10/22 01:08, Arnd Bergmann wrote: > On Sat, Oct 22, 2022, at 10:07, Greg Kroah-Hartman wrote: >> On Sat, Oct 22, 2022 at 03:35:48PM +1100, Scott J. Crouch wrote: > >> Nice try, but this breaks the build in a very horrible and strange way >> that no one has been able to figure out yet: > > I got curious and figured out what happens: > > Without CONFIG_OF, of_match_node() always returns NULL, so > vchiq_probe() returns -EINVAL unconditionally before calling > vchiq_platform_init(). > > If vchiq_platform_init() is marked 'static', gcc's dead code > elimination then eliminates it, which in turn means that > 'g_fragments_base' is never initialized and gets replaced > with a NULL pointer. Good spotting. Actually, I was clumsily learning how to run sparse on the staging directory and wasn't sure what config to use that didn't involve enabling everything manually. But from what I can tell, it's OF_OVERLAY (or something downstream of that) that gets rid of the warning. BCM2835_VCHIQ requires BCM_VIDEOCORE which already depends on OF. I'm confused because I don't actually know how to reproduce the gcc warning without manually enabling the module such that OF is enabled but OF_OVERLAY isn't, since allmodconfig enables both -- maybe there's a way to do that. I'm also confused why devm_rpi_firmware_get() doesn't have the same problem as of_match_node() just above it -- it returns NULL when RASPBERRYPI_FIRMWARE is unset, but gcc still builds without the warning. Scott.
