Subject: Re: [spi-devel-general] [PATCH 2/3] [SPI] Add new mode: SPI_LOOP

From: Ned Forrester <[email-masked]>
Date: Thu, 26 Jul 2007 23:34:45 -0400

David Brownell wrote:
> On Thursday 26 July 2007, Anton Vorontsov wrote:
>> Loopback mode is supported by various controllers, this mode
>> is useful for testing, especially in conjunction with spidev
>> driver.
> 
> ISTR that Stephen Street provided a loopback mode for debug
> in his pxa2xx_spi code.  And I know you're fight that this
> mode shows up in a lot of hardware.
> 
> Comments, anyone?  This seems like a fair way to expose this
> mechanism.  And I tend to agree that it'd mostly be useful in
> conjunction with "spidev".

Yes, it is in pxa2xx_spi.  It is passed in a structure that is attached 
to spi_board_info.controller_data.  I have used it to great effect to 
test data modes in the driver for which I have no external hardware 
support: various bits/word, clock frequencies, fifo thresholds, dma 
burst sizes, etc.

It works for me if this is moved to struct spi_device.

I don't think I have any code that could be readily turned into a 
generic test program.

-- 
Ned Forrester                                       [email-masked]
Oceanographic Systems Lab                                  508-289-2226
Applied Ocean Physics and Engineering Dept.
Woods Hole Oceanographic Institution          Woods Hole, MA 02543, USA
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