Re: Questions about i2c_transfer() usage in timer context...

[Stephane Grosjean <s.grosjean-g4cQ8AsIbFbL9ATBNaCtXw@public.gmane.org>]

Merci Jean,

Thx for the quick answer. I think this will help.

Stéphane

Le 20/02/2012 14:11, Jean Delvare a écrit :
> Bonjour Stéphane,
>
> On Mon, 20 Feb 2012 14:01:52 +0100, Stephane Grosjean wrote:
>> I'm facing a deadlock regarding a timer callback which is only calling
>> i2c_transfer(), and I wonder if this comes from that call: I first
>> googled and found that i2c_transfer() may sleep (which is forbidden in
>> my timer callback) but when I have a look the beginning of the function,
>> it starts to check if it is in any atomic context, before trying to
>> acquire  a lock...
>>
>> So I'm afraid I'm lost and I hope someone will be able to understand to
>> that question: might i2c_transfer() be used in a timer callback or
>> should I handle my periodic call to i2c_tranfer() by means of a delayed
>> work?
> Depends on the underlying I2C adapter driver. One of the sleep causes
> is indeed the acquisition of the mutex in i2c_transfer(). However the
> function then calls a driver specific callback function
> (adap->algo->master_xfer) which may or may not sleep too depending on
> the implementation. So if you want your code to be portable, you have to
> assume that it may sleep, which means you indeed have to use a delayed
> work.
>
> HTH,