Re: recursive locking problem

[Antti Palosaari <crope@iki.fi>]

On 09/14/2011 09:19 AM, Daniel Glöckner wrote:
> On Wed, Sep 14, 2011 at 04:03:58AM +0300, Antti Palosaari wrote:
>> On 09/09/2011 02:46 PM, Daniel Glöckner wrote:
>>> On Thu, Sep 08, 2011 at 07:34:32PM +0300, Antti Palosaari wrote:
>>>> I am working with AF9015 I2C-adapter lock. I need lock I2C-bus since
>>>> there is two tuners having same I2C address on same bus, demod I2C
>>>> gate is used to select correct tuner.
>>>
>>> Would it be possible to use the i2c-mux framework to handle this?
>>> Each tuner will then have its own i2c bus.
>>
>> Interesting idea, but it didn't worked. It deadlocks. I think it
>> locks since I2C-mux is controlled by I2C "switch" in same I2C bus,
>> not GPIO or some other HW.
>
> Take a look at drivers/i2c/muxes/pca954x.c. You need to use
> parent->algo->master_xfer/smbus_xfer directly as the lock that
> protects you from having both gates open is the lock of the
> root i2c bus.

Ah yes, rather similar case. I see it as commented in pca954x.c:
/* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
    for this as they will try to lock adapter a second time */

This looks even more hackish solution than calling existing demod 
.i2c_gate_ctrl() callback from USB-interface driver. But yes, it must 
work - not beautiful but workable workaround.


regards
Antti

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