avoid warning messages from ahci and other controllers
when turning dma on by selecting only ide controllers from
#S/sdctl.

Reference: /n/sources/patch/maybe/dmaon
Date: Mon Aug  3 15:06:05 CES 2009
Signed-off-by: quanstro@quanstro.net

--- /rc/bin/dmaon	Mon Aug  3 15:05:20 2009
+++ /rc/bin/dmaon	Mon Aug  3 15:05:18 2009
@@ -1,7 +1,12 @@
 #!/bin/rc
 # dmaon - turn on ide dma, if possible
 rfork e
-for (ctl in /dev/sd[C-H]?/ctl)
-	if (test -e $ctl && grep -s '^config .* dma ' $ctl &&
-	    ! grep -s '^config (848A|.* dma 00000000 )' $ctl)
-		echo 'dma on' >$ctl
+if(! test -f '#S/sdctl')
+	exit ''
+ctlrs=`{sed -n 's/(^sd.) ata .*/\1/p' <'#S/sdctl'}
+if(~ $#ctlrs 0)
+	exit ''
+for(ctl in '#S/'$ctlrs^?/ctl)
+	if (! grep -s '^config .* dma 00000000 ' $ctl)
+		echo dma on >$ctl [2]>/dev/null || echo dmaon: $ctlr failed
+