[util] Add romcheck.pl

Provide a utility to quickly determine the ROM size and .mrom format
support for attached PCI devices.  For example:

    01:00.0 (1186:4300) supports a 128kB .rom or .mrom

Inspired-by: Wes Frazier <wes.frazier@members.fsf.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/util/romcheck.pl

@@ -0,0 +1,54 @@
+#!/usr/bin/perl -w
+
+use strict;
+use warnings;
+
+use constant DEVICES => "/proc/bus/pci/devices";
+
+open my $fh, DEVICES
+    or die "Could not open ".DEVICES.": $!";
+
+while ( ( my $line = <$fh> ) ) {
+
+  # Parse line from /proc/bus/pci/devices
+  chomp $line;
+  ( my $bus, my $devfn, my $vendor, my $device, my $irq, my $bars, my $lengths,
+    my $driver )
+      = ( $line =~ /^ ([0-9a-f]{2}) ([0-9a-f]{2}) \s+
+		      ([0-9a-f]{4}) ([0-9a-f]{4}) \s+ ([0-9a-f]+) \s+
+		      ((?:[0-9a-f]+\s+){7}) ((?:[0-9a-f]+\s+){7})
+		      (.+)?$/x )
+      or die "Invalid line \"".$line."\"\n";
+  ( $bus, $devfn, $vendor, $device, $irq ) =
+      map { hex ( $_ ) } ( $bus, $devfn, $vendor, $device, $irq );
+  my $dev = ( $devfn >> 3 );
+  my $fn = ( $devfn & 0x7 );
+  $bars = [ map { hex ( $_ ) } split ( /\s+/, $bars ) ];
+  $lengths = [ map { hex ( $_ ) } split ( /\s+/, $lengths ) ];
+
+  # Calculate expansion ROM BAR presence and length
+  my $rom_length = $lengths->[6];
+
+  # Look for a BAR that could support a .mrom
+  my $mrom_ok;
+  if ( $rom_length ) {
+    for ( my $bar = 0 ; $bar < 7 ; $bar++ ) {
+      # Skip I/O BARs
+      next if $bars->[$bar] & 0x01;
+      # Skip low half of 64-bit BARs
+      $bar++ if $bars->[$bar] & 0x04;
+      # Skip 64-bit BARs with high dword set
+      next if $bars->[$bar] >> 32;
+      # Skip BARs smaller than the expansion ROM BAR
+      next if $lengths->[$bar] < $rom_length;
+      # This BAR is usable!
+      $mrom_ok = 1;
+      last;
+    }
+  }
+
+  printf "%02x:%02x.%x (%04x:%04x)", $bus, $dev, $fn, $vendor, $device;
+  printf " supports a %dkB .rom", ( $rom_length / 1024 ) if $rom_length;
+  printf " or .mrom" if $mrom_ok;
+  printf "\n";
+}