On Sun, May 27, 2001 at 05:15:19PM -0700, Matthew Jacob wrote:
> 
> (Top of Tree -current)
> 
> Hmm- I changed MAXBSIZE to 128*1024 && MAXPHYS to 1024*1024.....
> 
> but then when I was doing some large filesystem XFER stuff on a SCSI based
> filesystem (I boot off of IDE on this PC164), apparently in the swap area, I
> got....
> 
> What's a poor fella to do :-)?
> 
> I rather suspect that some limit checks about breaking up large transfers for
> DMA is in order here...

IDE can't handle xfers larger than 64K, and this is a hardware limitation
(the size of the sector count register). I suspect ATAPI doesn't have this
limitation, though.
I suspect some older SCSI adapters have a hardware limit too.

What we need here is get rid of MAXBSIZE & MAXPHYS as #define, and have
a per-device info for this. Maybe get rid of minphys completely in
physio, and remplace it by a maxphys variable in struct disk or struct
dkdriver. Disks users could then limit their xfer against this variable.

But for now I fear we're stuck at 64k :(

--
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
--