On Fri, Oct 25 2002, Stephen Cameron wrote:
>
> Add blk_rq_map_sg_one_by_one function to ll_rw_blk.c in order to allow a low
> level driver to map scatter gather elements from the block subsystem one
> at a time into device specific data structures instead of having to take
> a copy of all of them all at once and then afterwards copy them into a device
> specific format.
>
> To follow, a patch to the cciss driver using this interface which
> allows up to 256 scatter gather elements (current limit is 31).
I have to say that I think this patch is ugly, and a complete duplicate
of existing code. This is always bad, especially in the case of
something not really straight forward (like blk_rq_map_sg()). A hack.
I can understand the need for something like this, for drivers that
can't use a struct scatterlist directly. I'd rather do this in a
different way, though.
__blk_rq_map(q, rq, sglist, callback)
{
...
/* do the mapping *.
if (sglist) {
sglist[nsegs].page = bvec->bv_page;
...
} else
callback(q, bvec, nsegs);
}
blk_rq_map_rq(q, rq, sglist)
{
return __blk_rq_map(q, rq, sglist, NULL);
}
blk_rq_map_callback(q, rq, callback)
{
return __blk_rq_map(q, rq, NULL, callback);
}
Or use a cookie like you currently do.
Oh, and do try to follow the style. It's
if (cond)
foo();
not
if (fond) foo();
-- Jens Axboe- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu Oct 31 2002 - 22:00:28 EST