On Mon, Jun 06, 2011 at 07:12:20PM +0900, FUJITA Tomonori wrote: > On Mon, 6 Jun 2011 10:47:51 +0100 > Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > > > On Mon, Jun 06, 2011 at 06:41:09PM +0900, FUJITA Tomonori wrote: > > > On Mon, 6 Jun 2011 10:14:10 +0100 > > > Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > > > > > > > On Mon, Jun 06, 2011 at 05:06:03PM +0900, FUJITA Tomonori wrote: > > > > > max_segs isn't unrelated with the dma mapping API. I explained above, > > > > > IOMMUs doesn't increase the number of segments (could decrease the > > > > > number of segments by merging). > > > > > > > > > > The limitation about the number of segment already lives elsewhere > > > > > (e.g. queue's limits.max_segments). > > > > > > > > I think you're missing the point entirely. > > > > > > > > Lets take the problem at hand: you have two devices. One of them is > > > > handled by the DMA engine code. One of them is a block device. > > > > > > > > The block layer needs to know the various parameters of what is > > > > allowable for DMA, including such things as the maximum size of a > > > > segment, and the _number_ of segments that can be placed into any > > > > one request. > > > > > > > > As the DMA provider is _entirely_ separate and unknown to the block > > > > device driver, the block device driver has no way to sanely provide > > > > these parameters to the block layer - they are not a property of the > > > > block device driver, but of the DMA provider. > > > > > > struct device_dma_parameters is used for a property of the block > > > device drivers (and scsi HBA drivers, etc). Not DMA provider. Right? > > > > Wrong. struct device_dma_parameters is a property of the _DMA_ _provider_. > > It has to be. Read what I said above and think about it. > > I think that it's up to your definition of DMA provider. I give up. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
