dumping large buffers to file

Valdis.Kletnieks at vt.edu Valdis.Kletnieks at vt.edu
Tue Nov 24 11:17:26 EST 2015

On Tue, 24 Nov 2015 06:30:22 +0000, Ramon Fried said:

> I'm currently debugging a ISP DMA issue in a kernel module.
> For debugging, I would like to dump buffers to a file on run time.
> The buffers are quite big, 1MB at least.

The *other* question is how *often* you plan to do this.  Doing it
once a second is one thing, doing it once a millisecond is another.

> I can think of numerous ways of transferring the buffer to user space and
> saving it by a dedicated user process (Netlink, sysfs, char device, etc.)

sysfs is probably a bad choice due to its 'one attribute per file' rule,
debugfs would be a better approach.  netlink is probably an option, and
it's hard to argue with the simplicity of a char device with a plain
old 'tail -f /dev/my-debug-file > /tmp/debug.out' or similar...

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