Messages in this thread | | | Date | Wed, 25 Apr 2001 14:37:06 -0500 (CDT) | From | Jesse Pollard <> | Subject | Re: /proc format (was Device Registry (DevReg) Patch 0.2.0) |
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--------- Received message begins Here ---------
> > On Wednesday 25 April 2001 19:10, you wrote: > > The command > > more foo/* foo/*/* > > will display the values in the foo subtree nicely, I think. > > Unfortunately it displays only the values. Dumping numbers and strings > without knowing their meaning (and probably not even the order) is not very > useful. > > > Better to factor the XML part out to a userspace library... > > But the one-value per file approach is MORE work. It would be less work to > create XML and factor out the directory structure in user-space :) > Devreg collects its data from the drivers, each driver should contribute the > information that it can provide about the device. > Printing a few values in XML format using the functions from xmlprocfs is as > easy as writing > proc_printf(fragment, "<usb:topology port=\"%d\" portnum=\"%d\"/>\n", > get_portnum(usbdev), usbdev->maxchild); > > Extending the devreg output with driver-specific data means registering a > callback function that prints the driver's data. The driver should use its > own XML namespace, so whatever the driver adds will not break any > (well-written) user-space applications. The data is created on-demand, so the > values can be dynamic and do not waste any space when devreg is not used. > > The code is easy to read and not larger than a solution that creates static > /proc entries, and holding the data completely static would take much more > memory. And it takes less code than a solution that would create the values > in /proc dynamically because this would mean one callback per file or a > complicated way to specify several values with a single callback.
Personally, I think
proc_printf(fragment, "%d %d",get_portnum(usbdev), usbdev->maxchild);
(or the string "dddd ddd" with d representing a digit)
is shorter (and faster) to parse with
fscanf(input,"%d %d",&usbdev,&maxchild);
Than it would be to try parsing
<usb:topology port="ddddd" portnum="dddd">
with an XML parser.
Sorry - XML is good for some things. It is not designed to be a interface language between a kernel and user space.
I am NOT in favor of "one file per value", but structured data needs to be written in a reasonable, concise manner. XML is intended for communication between disparate systems in an exreemly precise manner to allow some self documentation to be included when the communication fails.
Even Lisp S expressions are easier :-)
------------------------------------------------------------------------- Jesse I Pollard, II Email: pollard@navo.hpc.mil
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