How do the CAN drivers get loaded?

Mike Worster

I'm trying to understand how CAN drivers get loaded into the TI AM335x based Linux system. When I check the output of lsmod:

[root /usr]# lsmod
Module                  Size Used by
c_can_platform          4172 0
c_can                   8180 1 c_can_platform
can_dev                 6951 1 c_can

I can see the CAN drivers in the system and when I run a dmesg I can see them being loaded:

[ 3.745933] CAN device driver interface
[ 3.891592] c_can_platform 481cc000.d_can: c_can_platform device registered (regs=fa1cc000, irq=68)

but I don't know what loads them. I've noticed there's no /etc/modules or /etc/modules.conf file and I can't seem to find any "modprobe" or "insmod" calls in the /etc/init.d scripts which load the CAN drivers.

So where are these loaded? And as a general side note, is there anyway to determine what mechinsm/scripts was used to load a driver to begin with?

over 10 years ago

0 Yordan Kovachev over 10 years ago

TI__Guru**** 161600 points

Hi Mike,

Can you share which TI SDK version are you using?

Check the defconfig file in your sources. It is possible that CAN drivers are NOT built as loadable modules (m), but built in the kernel image (y).

Best Regards,
Yordan

0 Mike Worster over 10 years ago in reply to Yordan Kovachev

Expert 1575 points

Hi Yordan,

Yordan Kovachev said:

Can you share which TI SDK version are you using?

It is version 07.00.00.00

Yordan Kovachev said:

It is possible that CAN drivers are NOT built as loadable modules (m), but built in the kernel image (y).

Nope, I can see the modules loaded:

[root /etc]# lsmod
Module Size Used by
c_can_platform 4172 0
c_can 8180 1 c_can_platform
can_dev 6951 1 c_can

They exist as .ko's on the system:

[root /etc]# ls /lib/modules/`uname -r`/kernel/drivers/net/can
c_can can-dev.ko
[root /etc]# ls /lib/modules/`uname -r`/kernel/drivers/net/can/c_can
c_can.ko c_can_platform.ko

And in the defconfig file they are clearly set as modules:

#
# CAN Device Drivers
#
# CONFIG_CAN_VCAN is not set
# CONFIG_CAN_SLCAN is not set
CONFIG_CAN_DEV=m
CONFIG_CAN_CALC_BITTIMING=y
# CONFIG_CAN_LEDS is not set
# CONFIG_CAN_AT91 is not set
# CONFIG_CAN_TI_HECC is not set
# CONFIG_CAN_MCP251X is not set
# CONFIG_CAN_FLEXCAN is not set
# CONFIG_PCH_CAN is not set
# CONFIG_CAN_GRCAN is not set
# CONFIG_CAN_SJA1000 is not set
CONFIG_CAN_C_CAN=m
CONFIG_CAN_C_CAN_PLATFORM=m

So I am quite confident they are not built into the kernel.

0 Yordan Kovachev over 10 years ago in reply to Mike Worster

TI__Guru**** 161600 points

Hi Mike,

Have you done any modifications to your kernel?

I just tested prebuilt images from SDK7.0 on my beaglebone black and I didn't see the behavior you describe.

Here is the result from my test:

1. boot up BBB with SDK7.0:

am335x-evm login: root

root@am335x-evm:~# ls

root@am335x-evm:~#

root@am335x-evm:~# lsmod

Module Size Used by

g_mass_storage 1787 0

usb_f_mass_storage 32479 2 g_mass_storage

libcomposite 30114 2 usb_f_mass_storage,g_mass_storage

configfs 19119 3 libcomposite,usb_f_mass_storage

bufferclass_ti 5405 0

omaplfb 11426 0

cryptodev 31027 1

musb_dsps 6511 0

musb_hdrc 52593 1 musb_dsps

snd_soc_omap 2494 0

snd_pcm_dmaengine 2997 1 snd_soc_omap

snd_soc_core 99221 1 snd_soc_omap

snd_compress 7419 1 snd_soc_core

regmap_spi 1469 1 snd_soc_core

snd_pcm 66734 3 snd_soc_core,snd_soc_omap,snd_pcm_dmaengine

snd_page_alloc 4843 1 snd_pcm

snd_timer 16028 1 snd_pcm

snd 45368 4 snd_soc_core,snd_timer,snd_pcm,snd_compress

soundcore 4767 1 snd

pvrsrvkm 175491 2 bufferclass_ti,omaplfb

musb_am335x 1199 0

2. Insert can modules:

root@am335x-evm:~# cd /lib/modules/3.12.10-ti2013.12.01/kernel/drivers/net/can

root@am335x-evm:/lib/modules/3.12.10-ti2013.12.01/kernel/drivers/net/can# insmod can-dev.ko

[ 176.598823] CAN device driver interface

root@am335x-evm:/lib/modules/3.12.10-ti2013.12.01/kernel/drivers/net/can# cd c_can

root@am335x-evm:/lib/modules/3.12.10-ti2013.12.01/kernel/drivers/net/can/c_can# insmod c_can.ko

root@am335x-evm:/lib/modules/3.12.10-ti2013.12.01/kernel/drivers/net/can/c_can# insmod c_can_platform.ko

And only after this I have the can drivers loaded in the kernel:

root@am335x-evm:/lib/modules/3.12.10-ti2013.12.01/kernel/drivers/net/can/c_can# cd ~