Hi Pali, On 5/13/23 02:13, Pali Rohár wrote: > On Friday 12 May 2023 22:58:04 Randy Dunlap wrote: >> In a randconfig with CONFIG_SERIAL_CPM=m and >> CONFIG_PPC_EARLY_DEBUG_CPM=y, there is a build error: >> ERROR: modpost: "udbg_putc" [drivers/tty/serial/cpm_uart/cpm_uart.ko] >> undefined! >> >> The build can be fixed by exporting "udbg_putc" in udbg.c. >> >> OTOH, maybe something like this is more appropriate in >> arch/powerpc/Kconfig.debug? >> >> config PPC_EARLY_DEBUG_CPM >> bool "Early serial debugging for Freescale CPM-based serial ports" >> - depends on SERIAL_CPM >> + depends on SERIAL_CPM=y >> >> Signed-off-by: Randy Dunlap <rdun...@infradead.org> >> Cc: Michael Ellerman <m...@ellerman.id.au> >> Cc: Nicholas Piggin <npig...@gmail.com> >> Cc: Christophe Leroy <christophe.le...@csgroup.eu> >> Cc: linuxppc-dev@lists.ozlabs.org >> Cc: Arnd Bergmann <a...@arndb.de> >> Cc: "Pali Rohár" <p...@kernel.org> >> --- >> arch/powerpc/kernel/udbg.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff -- a/arch/powerpc/kernel/udbg.c b/arch/powerpc/kernel/udbg.c >> --- a/arch/powerpc/kernel/udbg.c >> +++ b/arch/powerpc/kernel/udbg.c >> @@ -14,6 +14,7 @@ >> #include <asm/udbg.h> >> >> void (*udbg_putc)(char c); >> +EXPORT_SYMBOL(udbg_putc); >> void (*udbg_flush)(void); >> int (*udbg_getc)(void); >> int (*udbg_getc_poll)(void); > > Hello! I do not think that it is a good idea to export udbg functions > for kernel modules. I have quickly looked at the cpm_uart driver file
Sure, that was just a conversation starter. > drivers/tty/serial/cpm_uart/cpm_uart_core.c and it looks like that once > udbg from it is registered then there is no code for unregistering it. > So I have feeling that compiling cpm_uart driver as module should not be > allowed when CONFIG_SERIAL_CPM_CONSOLE is enabled, and early debug > should depend on CONFIG_CONSOLE_POLL || CONFIG_SERIAL_CPM_CONSOLE. The other change above also fixes the build error: (Option 2) >> config PPC_EARLY_DEBUG_CPM >> bool "Early serial debugging for Freescale CPM-based serial ports" >> - depends on SERIAL_CPM >> + depends on SERIAL_CPM=y Also, making SERIAL_CPM (cpm_uart driver) be restricted to not allow it as a module when SERIAL_CPM_CONSOLE is enabled [how does one express that in Kconfig language?] will cause a circular dependency since SERIAL_CPM_CONSOLE depends on SERIAL_CPM=y. It looks like you are suggesting reversing the dependencies. > Any other opinion? Yes, please. Otherwise I prefer my option 2. -- ~Randy
