Re: Status of Linux SPI slave

["Girish" <girishsg-l0cyMroinI0@public.gmane.org>]

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>-----Original Message-----
>Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
>Subject: Re: [spi-devel-general] Status of Linux SPI slave
>
>Roger Frøysaa wrote:
>> Hi.
>>
>
>For example, I have an SPI master device that streams data to a Linux
>processor at 11Mbit/sec, but never expects any response from the
>processor; this data is written over the 100baseT network to an NFS
>file system at an effective 5GBytes/hour.  To make it work, I have
>heavily modified the pxa2xx-spi driver for the target Gumstix system so
>that it can accept data driven by an external clock, and so that it uses
>a queue of DMA descriptors to prevent interrupt latency from limiting
>service of the receive FIFO.  I did not have to modify a single line of
>code anywhere else in the SPI framework.  All other parts of the SPI
>framework, as well as my protocol driver and user-space code, still
>operate as if they were part of an SPI master; they just keep full a
>queue of SPI messages that request buffers to be filled by SPI reads.
>Basically, this is a VERY limited slave function, where the Linux system
>is not in control of the timing, but also there is never any sort of
>query/response between the master and slave.

Well, now I get the minimal use of slave side transfer. As David suggested
of having spi_slave struct wrapping the hardware, have you thought of
something like that and how would your existing pxa2xx-spi driver will be
impacted?
And thanks for starting this thread:).
Actually, in my case I had to modify controller driver to support SPI in
master and slave mode as well, with standard transfers (half/full duplex
communication).

Regards,
Girish

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