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From: Grant Likely <grant.likely-s3s/>
To: Linus Walleij <>
Cc: spi mailing list
	Ken Mills <>
Subject: Re: [PATCH] Add support for slave controllers plus sysfs entries for power management
Date: Tue, 16 Feb 2010 15:07:28 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Feb 16, 2010 at 12:33 PM, Linus Walleij
<> wrote:
> 2010/2/15 jassi brar <>:
>> I don't think adding SPI_SLAVE support is just a matter of providing
>> additional callbacks and structures, as is pointed out in this thread....
> You mean that the responsiveness / control of latencies is the other thing
> that's needed? Yep so it is. But getting the infrastructure in place doesn't
> hurt because this is something many people (including self) need and Ken
> over at Intel is the only one actually doing something about it.

No, the model needs to be in place first.  That means describing the
model for spi_slave transfers.  Does the driver need to turn around
and respond mid-transfer?  Does there need to be latency controls?
How are protocol drivers interfaced with spi slave controllers (1 to
1, or 1 to many, how is the protocol selected)?

I appreciate the work Ken is doing, but the patches posted so far
abuse the spi_master model in a way I'm not willing to merge.  I think
spi_slave is a different enough thing that it warrants an entirely
different core infrastructure (but I do reserve the right to have my
mind changed).

> Getting SPI slaves to actually work by spawning their worker threads as
> realtime under that patchset is of course a larger issue. One does not
> exclude the other tho.

Your right, the realtime issues are separate, but I still need to see
how spi_slave devices are intended to work, and what the
strengths/limitations of the model are.


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  parent reply	other threads:[~2010-02-16 22:07 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-12-18 21:06 Ken Mills
2010-01-19 15:59 ` Grant Likely
     [not found]   ` <>
2010-02-14 23:20     ` Linus Walleij
     [not found]       ` <>
2010-02-15  1:37         ` jassi brar
     [not found]           ` <>
2010-02-16 19:33             ` Linus Walleij
     [not found]               ` <>
2010-02-16 20:48                 ` Ned Forrester
     [not found]                   ` <4B7B048C.8080205-/>
2010-02-17  3:19                     ` Grant Likely
2010-02-16 22:07                 ` Grant Likely [this message]
2010-02-17  1:43                 ` jassi brar
2010-02-16 22:01             ` Grant Likely

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