Subject: Re: Single file system (buf) read size
To: Jason R Thorpe <>
From: Andrew Doran <>
List: tech-kern
Date: 03/15/2001 22:26:21
Jason R Thorpe <> wrote:

> On Thu, Mar 15, 2001 at 10:07:51AM +0100, Pål Halvorsen wrote:
>  > In such a case, is it possible, without too much work - especially in the
>  > driver code which I do not know much about, to get > 64 KB read
>  > operations?
> Yah, you can do it -- just keep in mind that most drivers allocate
> DMA maps to map a 64k transfer -- you might need to frob the device
> drivers in question to allow larger transfers, but it's usually a
> matter of adjusting a single constant (and the rest of the things
> get re-computed automatically).

It's not always that simple.. Just off the top of my head, `iop' for
instance will need to be modified to use chained s/g lists (i.e. a pointer
to the real list in the message frame), and `mlx' won't do transfers larger
than 64kB no matter how much you want.