On Tue, Sep 2, 2014 at 2:07 PM, Stefan Fritsch <s...@sfritsch.de> wrote:
> On Tuesday 02 September 2014 13:15:19, Philip Guenther wrote:
>> On Tue, Sep 2, 2014 at 12:51 PM, Stefan Fritsch <s...@sfritsch.de>
> wrote:
>> > On Monday 01 September 2014 22:24:16, David Gwynne wrote:
>> > > > i haven't found a controller that does less than MAXPHYS.
>> > > > perhaps they meant to improve the situation but stopped short.
>> > >
>> > > if we wanted to raise MAXPHYS, we'd have to support older
>> > > controllers that cant do greater than 64k with some mechanism.
>> >
>> > So the summary of this thread is that
>> >
>> > - drivers have to support 64K transfers
>> > - the minphys mechanism is useless at the moment
>>
>> Useless? It works just fine for physio, which is what it was
>> designed for, no?
>> > Not quite what I hoped, but ok. Do you know a good place where
>> > this
>> > should be documented?
>>
>> minphys is currently documented on physio(9)
>
> From physio(9):
>
> minphys
> A device specific routine called to determine the maximum
> transfer size that the device's strategy routine can
> handle.
>
> Since we have seen that the driver must be able to handle 64k blocks
> in any case, the fact that minphys is device specific is useless,
> isn't it?
physio() is used by character device access. Looks to me like
sdminphys() will change the chunking behavior of this:
dd if=/dev/zero of=/dev/rsd0a bs=100M count=1
depending on whether sd0 is a SCSI-I device, no?
Philip Guenther
