Date: Wed, 04 Mar 2015 11:21:27 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: David Chisnall <theraven@freebsd.org>, Allan Jude <allanjude@freebsd.org> Subject: Re: Massive libxo-zation that breaks everything Message-ID: <15905806.StXgP74c8j@ralph.baldwin.cx> In-Reply-To: <B38C4D7E-05DC-4D35-A650-37A466FF9508@FreeBSD.org> References: <54F31510.7050607@hot.ee> <54F50F15.4050300@freebsd.org> <B38C4D7E-05DC-4D35-A650-37A466FF9508@FreeBSD.org>
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On Tuesday, March 03, 2015 09:09:43 AM David Chisnall wrote: > Hopefully there's a lesson here that we can learn from: human-readable > formats do not make good intermediate representations when communicating > between tools. I think this is actually an argument against libxo-ification in the one case where I've cringed a bit at the diffs: pciconf. The current pciconf code is tailored to outputting something human readable. For non-human output I would probably generate different output (not just put tags on the human output) because I would want the non-human output to be both more verbose and more raw. I think some other cases like 'netstat -s' are far more straightforward as the current output maps fairly well to the backing structure, but in general I would want machine-readable output that is closer to the structures than to the human-readable formatting of them. For example, for something like 'mfiutil show drives', I would want the human readable format to stay as it is (it only highlights certain fields in the PD structures) but I would want the machine-readable format to basically output tagged versions of the backing structures from sys/dev/mfi/mfireg.h. That way the machine-readable format has all of the data instead of only the subset that is presented in the human-readable output. So while I am in general a big fan of having machine-readable output from tools (and I think it belongs in the base system, and I don't think you want a post-processing tool), I think there is a bit of a flawed assumption that says that I want the same data in the human-readable format that I want in the machine-readable format. I, for one, don't. I want the human-readable form more condensed. > If your argument is about maintainability of these changes, then please > point to concrete instances where the changes are complex and difficult to > maintain. When I've looked at the xo diffs for pciconf, my reaction has been "ugh, I guess I'm not going to work on pciconf again in the future because that's super ugly". I don't object to the idea, I think I would just rather have a very different schema for machine-readable output. I would probably want pciconf -l in that case to dump the entire PCI header (right now the human- readable pciconf -l only dumps a subset), and I would want it to dump fields in capabilities that we don't currently bother printing (and that I don't think the human-readable output should print due to it being too obscure, etc.) -- John Baldwin
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