On 17 June 2011 14:40, Matthew Wilcox <matthew@xxxxxx> wrote: > On Thu, Jun 16, 2011 at 08:30:53PM +0800, Shawn Guo wrote: >> Here is the user story that tells the need of the new api. The >> mxs-mmc is the mmc host controller for Freescale MXS architecture. >> There are a pair of mmc host specific parameters max_seg_size and >> max_segs that mxs-mmc host driver needs to tell mmc core, so that >> mmc core can know how big each data segment could be and how many >> segments could be handled one time in a scatter list by host driver. >> >> The mxs-mmc driver is one user of dmaengine mxs-dma, and it will call >> mxs-dma to transfer data in scatter list. That is to say mxs-mmc has >> no idea of what max_seg_size and max_segs should be, because they are >> all mxs-dma capability parameters, and mxs-mmc needs to query them >> from mxs-dma. > > This approach would make sense if mxs-mmc were generic, but it's tied to > mxs-dma, so it can just as well call mxs-dma to find out how many segments > it supports. > mxs-dma use the generic dmaengine.h. The patch is not only intended for mxs-mmc. MMCI and other mmc host drivers need a way to query max_seg_number. It would be possible to store this number within drivers/dmaengine but this would not work for omap_hsmmc that doesn't use drivers/dmaengine Regards, Per -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
