Kernel driver variables (vpfe_capture)

John Anderson

I'd like to change the debug parameter of vpfe_capture on the fly. I remember that you could echo debug=1 into a file in the proc file system. But I can't remember what the file was or the location.

Does anyone know how to do this. What's weird is that I completely figured this out on my own a while back. And now that I know what I should be looking for I can't figure it out again. Should of took up an easier occupation like Doctor or Lawyer.

JohnA

over 14 years ago

0 Nagabhushana over 14 years ago

TI__Expert 4685 points

I believe you should set module parameter in u-boot. file name is vpfe_capture.c

http://arago-project.org/git/projects/?p=linux-davinci.git;a=blob;f=drivers/media/video/davinci/vpfe_capture.c;h=40b8ba52e8f4db1f21812303fe0a6324cb810639;hb=3df7eda25fe6477a6005556fce821dbe86475c8d

0 John Anderson over 14 years ago in reply to Nagabhushana

Genius 5240 points

Thanks Naga, but that isn't what I'm looking for. You can set the variable in the proc file system but I forgot how to do it.

JohnA

0 Prabhakar Lad over 14 years ago in reply to John Anderson

Guru 11260 points

hi john

in proc file system you cant set a variable using , systctl

http://www.frozentux.net/ipsysctl-tutorial/chunkyhtml/howtosetvariables.html

this might help you out.

Best Regards

Prabhakar Lad

0 John Anderson over 14 years ago in reply to Prabhakar Lad

Genius 5240 points

That would help except I don't know the key for the variable. For example...

sysctl -w vpfe_capture.debug=1 returns a bad key message.

JohnA

0 Norman Wong over 14 years ago

Guru 26430 points

Learned something myself about modules and sysfs. Google gave a few hits. This one is fairly descriptive:

http://www.linux.com/learn/linux-training/28065-the-kernel-newbie-corner-everything-you-wanted-to-know-about-module-parameters

Tracing through the source:

include/media/davinci/vpfe_capture.h
#define CAPTURE_DRV_NAME "vpfe-capture"

drivers/media/video/davinci/vpfe_capture.c
module_param(debug, bool, 0644);
MODULE_PARM_DESC(debug, "Debug level 0-1");
static struct platform_driver vpfe_driver = {
        .driver = {
                .name = CAPTURE_DRV_NAME,
                .owner = THIS_MODULE,
        },
        .probe = vpfe_probe,
        .remove = __devexit_p(vpfe_remove),
};

In theory, you should be able to read and write into the sysfs file

cat /sys/module/vpfe-capture/parameters/debug
echo 1 > /sys/module/vpfe-capture/parameters/debug

0 Prabhakar Lad over 14 years ago in reply to Norman Wong

Guru 11260 points

Hi Norman,

A slight correction, it should be "echo 1 > /sys/module/vpfe_capture/parameters/debug" , ie it should be the module name and not the capture driver name.

Best Regards

Prabhakar Lad

0 John Anderson over 14 years ago in reply to Prabhakar Lad

Genius 5240 points

Thanks guys. That was exactly what I was looking for.

JohnA

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Kernel driver variables (vpfe_capture)