Date: Wed, 19 Sep 2007 12:03:20 -0700 From: Marcel Moolenaar <xcllnt@mac.com> To: arch@freebsd.org Subject: Replacing/enhancing kernel printf() Message-ID: <96A863DB-3C0B-4AD0-B0A1-3C0A89B42C75@mac.com>
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All, With FreeBSD being used in various situations, including the embedded space, there seems to be an increasing need to have fine-grained control over what the kernel prints to the console during boot as well as during normal operation. It is my believe at least that the all or nothing approach that we have now is inadequate. With this email I'd like to start a discussion in an attempt to get some feel for what is possible and/or acceptable as well as get more information about the situations where the current behaviour of FreeBSD had to be changed (or people wished it would change). We currently have standard, verbose and mute. Standard is really already too verbose from a regular user (i.e. non-developer) point of view. Mute is really not adequate, because you may want to print at least the copyright notice or provide a couple of lines of critical information even when you don't wont to see anything else. On top of that, if we shift our thinking towards the theoretical, futuristical and/or luxurious then we may be faced with multiple output devices, such as a small LCD, onto which we want to print some status information. With multiple output devices we may want to channel different kinds of messages to different devices. As a first stab, I'm thinking that if we amend the printf()s with a syslog-type facility and/or level, we may achieve just that. Replacing printf with klog() and change the printf implementation to be in terms of a klog call with an as of yet unspecified level and/or facility would help migrate from one system to another. What do people think of such an ability? Have people implemented something similar as part of their own FreeBSD-based solutions? If we have the ability to suppress certain kinds of output, do we still want save the supressed output somewhere and do we want to be able to have fine-grained control over that too? Thanks, -- Marcel Moolenaar xcllnt@mac.com
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