Re: [PATCH][2.6] Add command function to struct i2c_adapter

From: Mark M. Hoffman (mhoffman_at_lightlink.com)
Date: 09/22/04

  • Next message: Jean Delvare: "Re: [PATCH][2.6] Add command function to struct i2c_adapter" 
    Date:	Wed, 22 Sep 2004 16:04:46 -0400
To: Adrian Cox <adrian@humboldt.co.uk>

    Hi Adrian:

    * Adrian Cox <adrian@humboldt.co.uk> [2004-09-22 19:32:31 +0100]:
    > 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.

    Yes, almost...

    Why force your card driver to re-implement i2c_smbus_read_byte() and all
    its relatives? Go ahead and define the i2c_client structure(s) as well,
    but don't i2c_attach_client(). Sensors drivers do their probing before
    attaching the client, so I know that works.

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

    Ditto, *plus* you can still reuse all the i2c_core helper routines that
    require a client structure.

    Regards, 

    -- 
Mark M. Hoffman
mhoffman@lightlink.com
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  • Next message: Jean Delvare: "Re: [PATCH][2.6] Add command function to struct i2c_adapter"

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