taglinefilesource code
HD_FEATURE223drivers/block/ide-cd.cOUT_BYTE (0, HD_FEATURE);
HD_FEATURE982drivers/block/ide.cOUT_BYTE(args[2],HD_FEATURE);
HD_FEATURE23include/linux/hdreg.h#define HD_PRECOMP HD_FEATURE  /* obsolete use of this port - predates IDE */