Skip to contentSkip to conversation

Debug output

DISCUSSION damateem 2 participants 3 messages Dec 1, 2011 Media (V4L/DVB)

lore
Share & tools
lore

damateem

author
#0 lore raw

There are a fair number of debug print statements in the V4L2 code. How do I turn those on?

For instance, I'd like the following code to print

if ((vfd->debug & V4L2_DEBUG_IOCTL) &&

                !(vfd->debug & V4L2_DEBUG_IOCTL_ARG)) {
        v4l_print_ioctl(vfd->name, cmd);
        printk(KERN_CONT "\n");
    }

so I can trace the IOCTL calls.

Thanks,
David

author
#1 lore raw

Ok, if I set debug as follows

vfd->debug =V4L2_DEBUG_IOCTL | V4L2_DEBUG_IOCTL_ARG;

I can see the debug trace in dmesg, but this doesn't seem like the correct way to set the flags.

What is the typical method of setting these debug flags?

Is this the best place to ask these type of questions?

Thanks,
David

Quoted 15 lines · damateem

There are a fair number of debug print statements in the V4L2 code. How do I turn those on?

For instance, I'd like the following code to print

if ((vfd->debug & V4L2_DEBUG_IOCTL) &&

                !(vfd->debug & V4L2_DEBUG_IOCTL_ARG)) {
        v4l_print_ioctl(vfd->name, cmd);
        printk(KERN_CONT "\n");
    }

so I can trace the IOCTL calls.

Thanks,
David

#2 lore raw
Quoted 6 lines · damateem

Ok, if I set debug as follows

vfd->debug =V4L2_DEBUG_IOCTL | V4L2_DEBUG_IOCTL_ARG;

I can see the debug trace in dmesg, but this doesn't seem like the correct way to set the flags.

In general, what it is none is to add a debug modprobe parameter that would enable those logs with something like:

static unsigned int debug;
module_param(debug, int, 0644);
MODULE_PARM_DESC(debug, "debug message mask (1 = ioctl, 2 = ioctl args)");

...

	vfd->debug = debug;
Quoted 29 lines

What is the typical method of setting these debug flags?

Is this the best place to ask these type of questions?

Thanks,
David

Quoted 11 lines · damateem

There are a fair number of debug print statements in the V4L2 code. How do I turn those on?

For instance, I'd like the following code to print

if ((vfd->debug& V4L2_DEBUG_IOCTL)&&

                 !(vfd->debug&  V4L2_DEBUG_IOCTL_ARG)) {
         v4l_print_ioctl(vfd->name, cmd);
         printk(KERN_CONT "\n");
     }
Quoted 4 lines

so I can trace the IOCTL calls.

Thanks,
David

--
To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html