sub devices sharing same i2c address

sub devices sharing same i2c address

[Karicheri, Muralidharan]

Hi,

I am having to switch between two sub devices that shares the same i2c address. First one is TVP5146 and the other is MT9T031. The second has a i2c switch and the evm has a data path switch. So in our internal release we could switch capture inputs between the two by configuring the above two switches. Right now, I am loading up the i2c sub devices using the new API (added by Hans) v4l2_i2c_new_subdev_board(). But since the i2c addresses are shared, it fails for the second sub device. Does someone know a way to get around this so that I could load up both sub devices and switch between them for capture?

Murali Karicheri
Software Design Engineer
Texas Instruments Inc.
Germantown, MD 20874
Phone : 301-515-3736
email: m-karicheri2@ti.com

Re: sub devices sharing same i2c address

[Daniel Glöckner]

On Tue, Jun 23, 2009 at 01:10:11PM -0500, Karicheri, Muralidharan wrote:
> I am having to switch between two sub devices that shares the same i2c
> address. First one is TVP5146 and the other is MT9T031. The second has
> a i2c switch and the evm has a data path switch.

You could try Rodolfo Giometti's i2c bus multiplexing code:
http://i2c.wiki.kernel.org/index.php/I2C_bus_multiplexing

It will create a new i2c_adapter for each output of the i2c switch
and the switch is handled transparently when accessing the devices.

  Daniel

RE: sub devices sharing same i2c address

[Karicheri, Muralidharan]

Daniel,

Thanks for responding....

Any reason why this is not added to upstream ? I think this is exactly what is needed to support this.

Murali Karicheri
Software Design Engineer
Texas Instruments Inc.
Germantown, MD 20874
Phone : 301-515-3736
email: m-karicheri2@ti.com

>-----Original Message-----
>From: Daniel Glöckner [mailto:daniel-gl@gmx.net]
>Sent: Tuesday, June 23, 2009 3:11 PM
>To: Karicheri, Muralidharan
>Cc: linux-media@vger.kernel.org
>Subject: Re: sub devices sharing same i2c address
>
>On Tue, Jun 23, 2009 at 01:10:11PM -0500, Karicheri, Muralidharan wrote:
>> I am having to switch between two sub devices that shares the same i2c
>> address. First one is TVP5146 and the other is MT9T031. The second has
>> a i2c switch and the evm has a data path switch.
>
>You could try Rodolfo Giometti's i2c bus multiplexing code:
>http://i2c.wiki.kernel.org/index.php/I2C_bus_multiplexing
>
>It will create a new i2c_adapter for each output of the i2c switch
>and the switch is handled transparently when accessing the devices.
>
>  Daniel

Re: sub devices sharing same i2c address

[Daniel Glöckner]

On Wed, Jun 24, 2009 at 12:44:08PM -0500, Karicheri, Muralidharan wrote:
> Any reason why this is not added to upstream ? I think this is exactly
> what is needed to support this.

IIRC it does not work reliably with the legacy i2c binding model, so this
has to die first.

  Daniel