On Tue, Apr 24, 2007 at 09:28:11PM +0200, Andi Kleen wrote: > On Tuesday 24 April 2007 08:03:03 Ashok Raj wrote: > > PCI specs permit zero length reads (ZLR) even if the mapping for that > > region > > is write only. Support for this feature is indicated by the presence of a > > bit > > in the DMAR capability. If a particular DMAR does not support this > > capability > > we map write-only regions as read-write. > > > > This option can also provides a workaround for some drivers that request > > a write-only mapping when they really should request a read-write. > > (We ran into one such case in eepro100.c in handling rx_ring_dma) > > Better just fix the drivers instead of adding such hacks
Some of the early DMAR's dont handle zero-length-reads as required. hardware that supports it correctly will advertise via its capabilities. We could remove the cmdline option since it should not be really required. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
