Re: [PATCH] i2c: skip address detection if provided in board_info

[Jacob Pan <jacob.jun.pan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

Hi Jean,

Jean Delvare Wed, 13 Oct 2010 09:26:54 +0200

>Devices don't have detect functions. Drivers do.
>
Yes, i understand. I was referring to i2c device driver vs adapter driver.
I will make it clearer next time.

>> Then all detect functions will be ignored
>> if i2c adpater class code is 0. The granularity of information provided by
>> our FW is per i2c device.
>> 
>> Seems we have three cases:
>> 1. adaptor class = 0, no detect
>> 2. adaptor class !=0, FW provide address via board info, no detect
>> 3. adaptor class !=0, no FW board info, do detect by default, but should
>> allow platform code override
>> 
>> I would think we need a global flag for case #3.
>
>You complain that the granularity of the current implementation is
>insufficient, but you propose to solve that problem using a _global_
>flag? This doesn't make sense, sorry.
>
to me, the global flag solves the problem where we want faster boottime
in all cases. so it is kinda of a different problem.

>There are actually two main cases, not three:
>
>1. Adapter class == 0, no detection, platform data provides all device
>   information.
>2. Adapter class != 0, detection of all devices, no platform data.
>
>Mixed cases aren't supported, because it is expected that all devices
>are declared as platform data, or none is. This seems to work OK so far
>for everybody. If it doesn't work for you, please explain why, in
>details.
>
it works for us in practice, at least for today. perhaps I am just playing
devil's advocate, but also for the completeness of the logic for future
use.

>Note though that there is some level of granularity because the adapter
>class is a bitfield. So it is possible to declare all I2C devices as
>platform data except the hardware monitoring devices, for example, and
>set adapter class = I2C_CLASS_HWMON.
>
>There aren't many bits really used, BTW, mostly I2C_CLASS_HWMON and
>I2C_CLASS_SPD, and the trend is to remove the unused class flags rather
>than to add new ones. However, if you need a new I2C_CLASS flag, this
>can certainly be done.
>

Can we make an explicit bit I2C_CLASS_NO_DETECT so that is is more
explicit? It also allows co-existance with other flags so that we can
handle mixed cases?

Thanks,
Jacob