Odd ada(4) failures when trying using USB scanner

[Alexander Motin]

Michael Reifenberger wrote:
> On Mon, 1 Feb 2010, Alexander Motin wrote:
> 
>> Date: Mon, 01 Feb 2010 14:18:17 +0200
>> From: Alexander Motin <mav at FreeBSD.org>
>> To: Michael Reifenberger <mike at reifenberger.com>
>> Cc: FreeBSD-Current <freebsd-current at freebsd.org>
>> Subject: Re: Odd ada(4) failures when trying using USB scanner
>>
>> Michael Reifenberger wrote:
>>> I'm using -current as of r202157.
>>>
>>> When attaching an epson USB scanner and trying to `scanimage -L`
>>> I get a freeze for some time and the following console logs:
>>> ...
>>> ata1: FAILURE - odd-sized DMA transfer attempt 5 % 2
>>> ata1: setting up DMA failed
>>
>> I would say that scanner application tries to probe all CAM devices,
>> looking for scanner. While doing it, it uses SCSI/ATAPI commands with
>> odd-sized transfer sizes. It causes errors from ata(4) and triggers bug
>> in IXP700 AHCI controller. Odd-sized requests are generally not
>> supported by ATA/SATA. Second problem is in work now.
> 
> Could odd-sized commands be prohibited/ignored by the driver then?

I've recently committed patch to 9-CURRENT, that should block sending of
SCSI commands to non-ATAPI devices. That should fix your problem.

-- 
Alexander Motin