linux-kernel - Re: [PATCH 1/2] spi: spidev: introduce SPI_IOC_WR_DEFAULT_MAX_SPEED

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Message-ID: <20170517090407.oc7d2hmydrsieli7@sirena.org.uk>
Date:   Wed, 17 May 2017 10:04:07 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Seraphime Kirkovski <kirkseraph@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org
Subject: Re: [PATCH 1/2] spi: spidev: introduce
 SPI_IOC_WR_DEFAULT_MAX_SPEED_HZ command

On Mon, May 15, 2017 at 10:17:11AM +0200, Seraphime Kirkovski wrote:
> On Sun, May 14, 2017 at 06:27:16PM +0900, Mark Brown wrote:

> > Do we have any evidence that such users exist?  

> I can't guarantee for other such users, but this change did disturb our 
> workflow. We were using this feature to prototype and test 
> hardware/firmware at different speeds.

> I was thinking this morning that maybe a sysfs interface will be better 
> for setting global settings. Do you prefer ?

I just don't see this as something that should be being varied at
runtime; it is supposed to be the maximum speed that the bus can be run
at, that's not something that should vary at runtime.  Possibly a sysfs
thing but honestly if you're prototyping via spidev I'd just set the
speed in your application each time it starts.

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