Subject: Re: [PATCH][2.6] Add command function to struct i2c_adapter
From: Adrian Cox <adrian@humboldt.co.uk>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       sensors@Stimpy.netroedge.com
Cc: Michael Hunold <hunold-ml@web.de>, Jon Smirl <jonsmirl@gmail.com>,
       Greg KH <greg@kroah.com>
In-Reply-To: <20040922122848.M14129@linux-fr.org>
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Date: Wed, 22 Sep 2004 19:32:31 +0100
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On Wed, 2004-09-22 at 14:38, Jean Delvare wrote:

> Aha, this is an interesting point (which was missing from your previous
> explanation). The base of your proposal would be to have several small i2c
> "trees" (where a tree is a list of adapters and a list of clients) instead of
> a larger, unique one. This would indeed solve a number of problems, and I
> admit that it is somehow equivalent to Michael's classes in that it
> efficiently prevents the hardware monitoring clients from probing the video
> stuff. The rest is just details internal to each "tree". As I understand it,
> each video device would be a tree on itself, while the whole hardware
> monitoring stuff would constitute one (bigger) tree. Correct?

I've been rereading the code, and it could be even simpler. How about
this:

1) The card driver defines an i2c_adapter structure, but never calls
i2c_add_adapter(). The only extra thing it needs to do is to initialise
the semaphores in the structure.
2) The frontend calls i2c_transfer() directly.
3) The i2c core never gets involved, and there is never any i2c_client
structure.

This gives us the required reuse of the I2C algo-bit code, without any
of the list walking or device probing being required.

- Adrian Cox
Humboldt Solutions Ltd.


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