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List:       linux-i2c
Subject:    Re: [PATCH 3/7] i2c: export bit-banging algo functions
From:       Jean Delvare <khali () linux-fr ! org>
Date:       2012-02-28 8:06:52
Message-ID: 20120228090652.627ac312 () endymion ! delvare
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On Mon, 27 Feb 2012 23:52:23 +0100, Daniel Vetter wrote:
> On Mon, Feb 27, 2012 at 11:20:40PM +0100, Jean Delvare wrote:
> > If you need to hot-switch between hardware and bit-banged I2C, I suggest
> > that you lock the bus while doing so, to avoid switching while a
> > transaction is in progress. This can be achieved with
> > i2c_lock_adapter() and i2c_unlock_adapter().
> 
> The drm/i915 xfer function is currently protected by a single mutex
> (because the hw i2c controller can only be used on one bus at a time). So
> I think we're covered. Also we do the fallback in our xfer function when
> we notice that things don't quite work as they should, so we actually want
> to switch while a transfer is in progress. Dunno whether that's the best
> approach, but the current code is structured like this.

This seems perfectly sane.

> (...)
> I've noticed that the the bit-banging algo does some test upon
> registration but figured that it's not worth the fuss to add a new init
> function that avoids the registration.

Note that thanks to the way things are implemented in i2c-algo-bit,
you'd really only have to write a new wrapper around
__i2c_bit_add_bus(), so this is really only 1 line of code. That being
said, I am not insisting, it's really up to you.

-- 
Jean Delvare
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