ports/122676: can't access dvd with any application that has been built by gcc4

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>Number:         122676
>Category:       ports
>Synopsis:       can't access dvd with any application that has been built by gcc4
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-ports-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Apr 12 00:00:05 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     
>Release:        RELENG_7
>Organization:
>Environment:
apr 5 7-stable, 32-bit i386
>Description:
applications that access dvd (mplayer/ogle/vobcopy) fail with the following message:

ata0: FAILURE - non aligned DMA transfer attempted
acd0: setting up DMA failed
acd0: FAILURE - REPORT_KEY ILLEGAL REQUEST asc=0x6f ascq=0x04 
ata0: FAILURE - non aligned DMA transfer attempted
acd0: setting up DMA failed
ata0: FAILURE - non aligned DMA transfer attempted
acd0: setting up DMA failed

it occurs when the application has been compiled with gcc4.
i also encountered this on 6.3 when compiling video applications with gcc42. rebuilding the affected applications with gcc34 works perfectly.
>How-To-Repeat:
attempt to play dvd with any software that has been built with gcc4. (oldest tried was 4.2.1 20070719, newest 4.2.4 20080326). all cause failure with same message.
>Fix:
workarounds:
recompile affected programs with gcc34
switch off dma on drive with atacontrol mode acd0 PIO4


>Release-Note:
>Audit-Trail:
>Unformatted: