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From: David Brownell <>
Cc: "Hemanth V" <>,
Subject: Re: [spi-devel-general] [RESEND][PATCH 0/2] McSPI Slave and DMA , FIFO support
Date: Thu, 27 Aug 2009 22:42:20 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <007b01c9fe05$9e5baeb0$LocalHost@wipultra793>

On Sunday 05 July 2009, Hemanth V wrote:
> Do you see any major changes required to support
> slave mode in the SPI core driver.

There *is* no such thing as a "SPI core driver"...

> We are able to 
> use the existing interface for slave mode also, but
> some APIs/ Structures could be made generic.

Three things are obvious:

 - A spi_master is not a slave side driver!

 - Control model would need to be inverted
    * Chip select would be one input,
      not N outputs
    * No clock rate controls at all
    * latency issues ... driver can't necessarily
      respond quickly enough to guarantee no data
      loss (FIFOs help)
    * Can't re-use /dev/spidev*
    * Request queue would have a very different role

 - Some primitives are likely missing, for flow
   control (when hardware has a READY handshake)

I think a few proposals for how to handle slave
side have been circulated.

  reply	other threads:[~2009-08-28  5:42 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-06-23 13:53 [RESEND][PATCH 0/2] McSPI Slave and DMA ,FIFO support Hemanth V
2009-07-03  0:05 ` David Brownell
2009-07-06  6:47   ` Hemanth V
2009-08-28  5:42     ` David Brownell [this message]
2009-08-28 12:05       ` [spi-devel-general] [RESEND][PATCH 0/2] McSPI Slave and DMA , FIFO support Hemanth V
2009-08-28 16:10         ` Tony Lindgren
2009-08-28 17:32         ` David Brownell

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