Hi Himanshu,
On 1/15/19 1:41 PM, Himanshu Jha wrote:
...
himanshu@himanshu-Vostro-3559:~/linux-next$ sudo make drivers/iio/chemical/bme680_spi.o
scripts/kconfig/conf --syncconfig Kconfig
make[1]: Nothing to be done for 'all'.
HOSTCC scripts/dtc/dtc.o
HOSTCC scripts/dtc/flattree.o
HOSTCC scripts/dtc/fstree.o
HOSTCC scripts/dtc/data.o
HOSTCC scripts/dtc/livetree.o
HOSTCC scripts/dtc/treesource.o
HOSTCC scripts/dtc/srcpos.o
HOSTCC scripts/dtc/checks.o
HOSTCC scripts/dtc/util.o
LEX scripts/dtc/dtc-lexer.lex.c
YACC scripts/dtc/dtc-parser.tab.h
HOSTCC scripts/dtc/dtc-lexer.lex.o
YACC scripts/dtc/dtc-parser.tab.c
HOSTCC scripts/dtc/dtc-parser.tab.o
HOSTLD scripts/dtc/dtc
CC scripts/mod/empty.o
MKELF scripts/mod/elfconfig.h
HOSTCC scripts/mod/modpost.o
CC scripts/mod/devicetable-offsets.s
HOSTCC scripts/mod/file2alias.o
HOSTCC scripts/mod/sumversion.o
HOSTLD scripts/mod/modpost
CC kernel/bounds.s
CC arch/x86/kernel/asm-offsets.s
CALL scripts/checksyscalls.sh
DESCEND objtool
CC drivers/iio/chemical/bme680_spi.o
Compiles without any issues.
Hum, weird it compiles actually :s
I think this behavior is observed due to:
include/linux/module.h +212
#ifdef MODULE
/* Creates an alias so file2alias.c can find device table. */
#define MODULE_DEVICE_TABLE(type, name) \
extern typeof(name) __mod_##type##__##name##_device_table \
__attribute__ ((unused, alias(__stringify(name))))
#else /* !MODULE */
#define MODULE_DEVICE_TABLE(type, name)
#endif
So, when we build the driver as a module[M] then macro expansion
takes place giving us the compiler warning.
OTOH, if the driver is built as builtin[*] then marco expands
to nothing or simply goes away. And `;' completes the struct
declaration while silencing the warning.
static const struct of_device_id bme680_of_spi_match[] = {
{ .compatible = "bosch,bme680", },
{},
}
MODULE_DEVICE_TABLE(of, bme680_of_spi_match);
converts to:
static const struct of_device_id bme680_of_spi_match[] = {
{ .compatible = "bosch,bme680", },
{},
}
;
^^^
Amazing!
Correct me if I'm wrong somewhere, took me 2 hours to figure
that out :D
Ahah, nice!
Thanks a lot for the explanation!
Also, I some additional interesting observations:
When buitin[*] -> no symbol tables in the RO segment of object file
himanshu@himanshu-Vostro-3559:~/linux-next$ nm drivers/iio/chemical/bme680_spi.o
0000000000000000 d __addressable_bme680_spi_driver_init130
00000000000001a0 r bme680_acpi_match
U bme680_core_probe
0000000000000000 r bme680_of_spi_match
00000000000000a0 d bme680_regmap_bus
U bme680_regmap_config
0000000000000000 t bme680_regmap_spi_read
0000000000000010 t bme680_regmap_spi_write
0000000000000000 d bme680_spi_driver
0000000000000000 t bme680_spi_driver_exit
0000000000000000 t bme680_spi_driver_init
00000000000001e0 r bme680_spi_id
0000000000000070 t bme680_spi_probe
U _dev_err
U __devm_regmap_init
U driver_unregister
0000000000000000 d __exitcall_bme680_spi_driver_exit
0000000000000000 t __initcall_bme680_spi_driver_init6
U regmap_read
U regmap_update_bits_base
U regmap_write
U spi_get_device_id
U __spi_register_driver
U spi_setup
U spi_write_then_read
U __stack_chk_fail
While when [M] -> we can see the symbol tables in the RO segment
himanshu@himanshu-Vostro-3559:~/linux-next$ nm drivers/iio/chemical/bme680_spi.o
00000000000001a0 r bme680_acpi_match
U bme680_core_probe
0000000000000000 r bme680_of_spi_match
00000000000000a0 d bme680_regmap_bus
U bme680_regmap_config
0000000000000000 t bme680_regmap_spi_read
0000000000000010 t bme680_regmap_spi_write
0000000000000000 d bme680_spi_driver
0000000000000000 t bme680_spi_driver_exit
0000000000000000 t bme680_spi_driver_init
00000000000001e0 r bme680_spi_id
0000000000000070 t bme680_spi_probe
0000000000000000 T cleanup_module
U _dev_err
U __devm_regmap_init
U driver_unregister
0000000000000000 T init_module
00000000000001a0 R __mod_acpi__bme680_acpi_match_device_table <---
0000000000000000 R __mod_of__bme680_of_spi_match_device_table <---
00000000000001e0 R __mod_spi__bme680_spi_id_device_table <---
U regmap_read
U regmap_update_bits_base
U regmap_write
U spi_get_device_id
U __spi_register_driver
U spi_setup
U spi_write_then_read
U __stack_chk_fail
U __this_module
0000000000000033 r __UNIQUE_ID_author38
000000000000000f r __UNIQUE_ID_description39
0000000000000000 r __UNIQUE_ID_license40
Thanks!
Thanks to you :)
