On Fri, 17 Jun 2011 06:40:35 -0600 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. SCSI HBA drivers stores the max number of sg entries in host->sg_tablesize (and scsi-ml tells the block layer about the limit)? So if we have the generic API to handle the value, scsi HBA drivers (and scsi-ml) could use it too? -- 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
