Date: Wed, 9 Apr 2003 14:01:58 -0600 From: "Kenneth D. Merry" <ken@kdm.org> To: "John S. Bucy" <bucy@ece.cmu.edu> Cc: freebsd-scsi@freebsd.org Subject: Re: cam: big transfers Message-ID: <20030409140158.A12245@panzer.kdm.org> In-Reply-To: <20030409194237.GI7726@catalepsy.ece.cmu.edu>; from bucy@ece.cmu.edu on Wed, Apr 09, 2003 at 03:42:38PM -0400 References: <20030409194237.GI7726@catalepsy.ece.cmu.edu>
index | next in thread | previous in thread | raw e-mail
On Wed, Apr 09, 2003 at 15:42:38 -0400, John S. Bucy wrote: > > Is it possible to do large (>MAXPHYS) bus transfers from a userland process > via cam? Not currently, no. You'd need to do some hacking around in cam_periph_mapmem() to allow for larger buffers. It actually checks against DFLTPHYS (64K) at the moment, not MAXPHYS, since some adapters (e.g. the Adaptec 1542) can't handle more than 17 S/G segments. If you just need larger buffers, and not performance, you could malloc a new kernel-space buffer to hold the user data. If you want performance as well, you could try writing your own routine that would map N pages from userland into the kernel, where N would be greater than MAXPHYS/PAGE_SIZE. If you just need say 256K transferred at a time, you could try bumping MAXPHYS to that and changing cam_periph_mapmem() to check against MAXPHYS as long as your hardware can support that. Ken -- Kenneth Merry ken@kdm.orghelp
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20030409140158.A12245>