See include/linux/compiler_attributes.h:
/*
* Add the pseudo keyword 'fallthrough' so case statement blocks
* must end with any of these keywords:
* break;
* fallthrough;
* goto <label>;
* return [expression];
*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
*/
-if __has_attribute(__fallthrough__)
- define fallthrough __attribute__((__fallthrough__))
-else
- define fallthrough do {} while (0) /* fallthrough */
-endif
The whole warning is quite long but looks like this:
CC [M] seeed-voicecard/ac108.o
In file included from ./include/linux/printk.h:331,
from ./include/linux/kernel.h:15,
from ./include/linux/list.h:9,
from ./include/linux/module.h:12,
from seeed-voicecard/ac108.c:15:
seeed-voicecard/ac108.c: In function ‘ac108_set_fmt’:
./include/linux/dynamic_debug.h:122:52: warning: this statement may fall through [-Wimplicit-fallthrough=]
122 | #define __dynamic_func_call(id, fmt, func, ...) do { \
| ^
./include/linux/dynamic_debug.h:143:2: note: in expansion of macro ‘__dynamic_func_call’
143 | __dynamic_func_call(__UNIQUE_ID(ddebug), fmt, func, ##__VA_ARGS__)
| ^~~~~~~~~~~~~~~~~~~
./include/linux/dynamic_debug.h:157:2: note: in expansion of macro ‘_dynamic_func_call’
157 | _dynamic_func_call(fmt,__dynamic_dev_dbg, \
| ^~~~~~~~~~~~~~~~~~
./include/linux/device.h:1795:2: note: in expansion of macro ‘dynamic_dev_dbg’
1795 | dynamic_dev_dbg(dev, dev_fmt(fmt), ##__VA_ARGS__)
| ^~~~~~~~~~~~~~~
seeed-voicecard/ac108.c:866:4: note: in expansion of macro ‘dev_dbg’
866 | dev_dbg(dai->dev, "used as slave when AC101 is master\n");
| ^~~~~~~
seeed-voicecard/ac108.c:868:2: note: here
868 | case SND_SOC_DAIFMT_CBS_CFS: /*AC108 Slave*/
| ^~~~
The semi-colon is needed, to prevent the comment being parsed as part of the "if {...}" statement.
The warning looks like this:
seeed-voicecard/wm8960.c: In function ‘wm8960_hw_params’:
seeed-voicecard/wm8960.c:752:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
752 | if ((iface & 0x3) != 0) {
| ^
seeed-voicecard/wm8960.c:757:2: note: here
757 | default:
| ^~~~~~~
Currently, installation is only supported on real hardware, but not
running in QEMU. Change the check to make sure the necessary
directories and programs are available instead of bailing out
on non-Raspberry archs.
