Fetch the repository succeeded.
After running make command, there will be two modules:
The fist module is our fake rtc driver, the second one is used to create a plateform device that matches our first module. This way, one can avoid updating the devicetree.
# insmod ./fake-pwm.ko
# insmod ./pwm-ins.ko
After loading both modules, one can print debug message, and see something like below:
# dmesg
[ 3390.052469] fake-rtc fake-rtc.0: rtc core: registered fake-rtc as rtc2
[ 3390.058033] fake-rtc fake-rtc.0: loaded; begin_time is 3390, rtc_time is 0
Before loading the module, there were no pwmchip4
# ls -l /sys/class/pwm/
lrwxrwxrwx 1 root root 0 Aug 12 17:54 pwmchip0 -> ../../devices/soc0/soc.0/2000000.aips-bus/2080000.pwm/pwm/pwmchip0
lrwxrwxrwx 1 root root 0 Aug 12 17:54 pwmchip1 -> ../../devices/soc0/soc.0/2000000.aips-bus/2084000.pwm/pwm/pwmchip1
lrwxrwxrwx 1 root root 0 Aug 12 17:54 pwmchip2 -> ../../devices/soc0/soc.0/2000000.aips-bus/2088000.pwm/pwm/pwmchip2
lrwxrwxrwx 1 root root 0 Aug 12 17:54 pwmchip3 -> ../../devices/soc0/soc.0/2000000.aips-bus/208c000.pwm/pwm/pwmchip3
But after loading modules,
# ls /sys/class/pwm/
pwmchip0 pwmchip1 pwmchip2 pwmchip3 pwmchip4
# ls -l /sys/class/pwm/
lrwxrwxrwx 1 root root 0 Aug 12 17:54 pwmchip0 -> ../../devices/soc0/soc.0/2000000.aips-bus/2080000.pwm/pwm/pwmchip0
lrwxrwxrwx 1 root root 0 Aug 12 17:54 pwmchip1 -> ../../devices/soc0/soc.0/2000000.aips-bus/2084000.pwm/pwm/pwmchip1
lrwxrwxrwx 1 root root 0 Aug 12 17:54 pwmchip2 -> ../../devices/soc0/soc.0/2000000.aips-bus/2088000.pwm/pwm/pwmchip2
lrwxrwxrwx 1 root root 0 Aug 12 17:54 pwmchip3 -> ../../devices/soc0/soc.0/2000000.aips-bus/208c000.pwm/pwm/pwmchip3
lrwxrwxrwx 1 root root 0 Aug 12 19:13 pwmchip4 -> ../../devices/platform/fake-pwm.0/pwm/pwmchip4
One can also check other parameters as below:
# cat /sys/class/pwm/pwmchip4/npwm
3
# udevadm info /sys/class/pwm/pwmchip4/
P: /devices/platform/fake-pwm.0/pwm/pwmchip4
E: DEVPATH=/devices/platform/fake-pwm.0/pwm/pwmchip4
E: SUBSYSTEM=pwm
The number of PWM that this chip provide is 3, as specified in the driver.
One may need to export the pwn #1 of this chip. It will then
appear in /sys/class/pwm/pwmchip4/.
# ls /sys/class/pwm/pwmchip4/
device export npwm power subsystem uevent unexport
# echo 1 > /sys/class/pwm/pwmchip4/export
# ls /sys/class/pwm/pwmchip4/
device npwm pwm1 uevent
export power subsystem unexport
# ls /sys/class/pwm/pwmchip4/pwm1/
duty_cycle enable period polarity power/ uevent
One can enable a pwm as below:
# echo 1 > /sys/class/pwm/pwmchip4/pwm1/enable
# dmesg
[...]
[ 5067.023859] Somebody enabled PWM device number 1 of this chip
One should remember that pwm indexes start from 0. I means for a chip that provide
3 pwm, there could be pwm0, pwm1, and pwm2. Let us check that, by trying
to export pmw3, which will trig an error:
# echo 3 > /sys/class/pwm/pwmchip4/export
sh: echo: write error: No such device
# echo 2 > /sys/class/pwm/pwmchip4/export
# ls /sys/class/pwm/pwmchip4/
device npwm pwm1 subsystem unexport
export power pwm2 uevent
Prior to unload the module, every exported pwm should be unexported.
# echo 1 > /sys/class/pwm/pwmchip4/unexport
# echo 2 > /sys/class/pwm/pwmchip4/unexport
此处可能存在不合适展示的内容，页面不予展示。您可通过相关编辑功能自查并修改。
如您确认内容无涉及 不当用语 / 纯广告导流 / 暴力 / 低俗色情 / 侵权 / 盗版 / 虚假 / 无价值内容或违法国家有关法律法规的内容，可点击提交进行申诉，我们将尽快为您处理。
马建仓 AI 助手