svn commit: r327101 - head/sys/dev/pccard

[Warner Losh]

Author: imp
Date: Sat Dec 23 06:11:19 2017
New Revision: 327101
URL: https://svnweb.freebsd.org/changeset/base/327101

Log:
  Expand cryptic comment with inforation I've learned in the mean time
  about CIS3/CIS4, including studies I've done on my large collection of
  PC Cards bought off e-bay over the years since the original entry as
  well as conversations I've had at conferences.

Modified:
  head/sys/dev/pccard/pccardvar.h

Modified: head/sys/dev/pccard/pccardvar.h
==============================================================================
--- head/sys/dev/pccard/pccardvar.h	Sat Dec 23 05:32:20 2017	(r327100)
+++ head/sys/dev/pccard/pccardvar.h	Sat Dec 23 06:11:19 2017	(r327101)
@@ -88,10 +88,18 @@ struct pccard_product {
 };
 
 /**
- * Note: There's no cis3 or cis4 reported for NOMATCH / pnpinfo events for pccard
- * It's unclear if we actually need that for automatic loading or not. These stirngs
- * are informative, according to the standard, but I have a dim memory of using these
- * strings to match things, though I can't find the example right now.
+ * Note: There's no cis3 or cis4 reported for NOMATCH / pnpinfo events for
+ * pccard It's unclear if we actually need that for automatic loading or
+ * not. These stirngs are informative, according to the standard. Some Linux
+ * drivers match on them, for example. However, FreeBSD's hardware probing is a
+ * little different than Linux so it turns out we don't need them. Some cards
+ * use CIS3 or CIS4 for a textual representation of the MAC address. In short,
+ * they aren't needed even though our friends in Linux have them. It is my
+ * belief that all the entries in Linux don't actually need to be separate there
+ * either, but it's hard to eliminate them and retest on old, possibly rare,
+ * hardware so they persist. Despite years of collecting ~300 different PC Cards
+ * off E-Bay, I've not been able to find any that need CIS3/CIS4 to select which
+ * device attaches.
  */
 #define PCCARD_PNP_DESCR "D:#;V32:manufacturer;V32:product;Z:cisvendor;Z:cisproduct;"
 #define PCCARD_PNP_INFO(t) \