As Jos Backus wrote ...
> On Tue, Jun 08, 1999 at 12:53:54AM -0600, Warner Losh wrote:
> > Isn't that 24 bits for addresses? You can dma from an ISA card to
> > anywhere in the first 16M...
>
> Arrgh, yes, I'm terribly confused. Sorry 'bout that.
Be happy, you're not alone ;-)
| / o / / _
: Tuesday, June 08, 1999 1:54 AM
Subject: Re: The choice of MAXPHYS
>In message <19990603231216.a36...@hal.mpn.cp.philips.com> Jos Backus
writes:
>: On Thu, Jun 03, 1999 at 07:30:20PM +0200, Wilko Bulte wrote:
>: > 20 bits. But older cards can do no more than 64 kB.
>:
>: I
On Tue, Jun 08, 1999 at 12:53:54AM -0600, Warner Losh wrote:
> Isn't that 24 bits for addresses? You can dma from an ISA card to
> anywhere in the first 16M...
Arrgh, yes, I'm terribly confused. Sorry 'bout that.
--
Jos Backus _/ _/_/_/ "Reliability means never
In message <19990603231216.a36...@hal.mpn.cp.philips.com> Jos Backus writes:
: On Thu, Jun 03, 1999 at 07:30:20PM +0200, Wilko Bulte wrote:
: > 20 bits. But older cards can do no more than 64 kB.
:
: Indeed, 20 bits (=1 Mbyte) for the address, 16 bits for the transfer counter
: (offset).
Isn't th
In message
Zhihui Zhang writes:
: The value of MAXPHYS is chosen to be 64K for the maximum raw I/O transfer
: size. I am wondering why it is not set larger.
I don't think that it is possible to guarantee that you can do a
larger write than 64k on a aha-1542 card given the worst case scatter
gath
>
> MAXPHYS is ultimately a limitation on the size of the b_pages array in
> the struct buf structure. The default is 128 KBytes. Device Drivers are
> supposed to break up I/O's into manageable sections themselves.
>
> Maybe when the buffer I/O / VFS subsystem is rewritten late
:On Thu, Jun 03, 1999 at 07:30:20PM +0200, Wilko Bulte wrote:
:> 20 bits. But older cards can do no more than 64 kB.
:
:Indeed, 20 bits (=1 Mbyte) for the address, 16 bits for the transfer counter
:(offset).
:
:--
:Jos Backus _/ _/_/_/ "Reliability means never
MAXPHY
On Thu, Jun 03, 1999 at 07:30:20PM +0200, Wilko Bulte wrote:
> 20 bits. But older cards can do no more than 64 kB.
Indeed, 20 bits (=1 Mbyte) for the address, 16 bits for the transfer counter
(offset).
--
Jos Backus _/ _/_/_/ "Reliability means never
As Zhihui Zhang wrote ...
>
> The value of MAXPHYS is chosen to be 64K for the maximum raw I/O transfer
> size. I am wondering why it is not set larger. The maxcontig value of FFS
> is default to be 16, which means 16*8192 or 128K bytes (twice as big as
> 64K) . If we raise the value of MAXPHYS,
As Jos Backus wrote ...
> On Thu, Jun 03, 1999 at 10:40:10AM -0400, Zhihui Zhang wrote:
> > The value of MAXPHYS is chosen to be 64K for the maximum raw I/O transfer
> > size. I am wondering why it is not set larger.
>
> Just a guess: maybe this has something to do with DMA address counters on ISA
On Thu, Jun 03, 1999 at 10:05:46AM -0600, Kenneth D. Merry wrote:
> I think the 64K value may have been chosen because cards like the Adaptec
> 1542 can't handle more than that.
That's exactly the card I was thinking about (I used to own one). So I was
close :)
--
Jos Backus
Jos Backus wrote...
> On Thu, Jun 03, 1999 at 10:40:10AM -0400, Zhihui Zhang wrote:
> > The value of MAXPHYS is chosen to be 64K for the maximum raw I/O transfer
> > size. I am wondering why it is not set larger.
>
> Just a guess: maybe this has something to do with DMA address counters on ISA
> c
On Thu, Jun 03, 1999 at 10:40:10AM -0400, Zhihui Zhang wrote:
> The value of MAXPHYS is chosen to be 64K for the maximum raw I/O transfer
> size. I am wondering why it is not set larger.
Just a guess: maybe this has something to do with DMA address counters on ISA
cards being 16 bit? (ducks) Or is
The value of MAXPHYS is chosen to be 64K for the maximum raw I/O transfer
size. I am wondering why it is not set larger. The maxcontig value of FFS
is default to be 16, which means 16*8192 or 128K bytes (twice as big as
64K) . If we raise the value of MAXPHYS, we can put more data blocks of a
big
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