linux-kernel - Re: [PATCH 03/11] Input: synaptics-rmi4 - do not update configuration in rmi_f01

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Date:	Tue, 18 Feb 2014 13:32:53 -0800
From:	Christopher Heiny <cheiny@...aptics.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Andrew Duggan <aduggan@...aptics.com>,
	Vincent Huang <vincent.huang@...synaptics.com>,
	Vivian Ly <vly@...aptics.com>,
	Daniel Rosenberg <daniel.rosenberg@...aptics.com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Courtney Cavin <courtney.cavin@...ymobile.com>,
	Linux Input <linux-input@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/11] Input: synaptics-rmi4 - do not update configuration
 in rmi_f01_probe()

On 02/17/2014 11:23 AM, Dmitry Torokhov wrote:
> On Fri, Feb 14, 2014 at 03:00:43PM -0800, Christopher Heiny wrote:
>> On 02/13/2014 01:54 PM, Dmitry Torokhov wrote:
>>> On Thu, Feb 13, 2014 at 11:23:44AM -0800, Christopher Heiny wrote:
>>>>> On 02/12/2014 09:27 PM, Dmitry Torokhov wrote:
>>>>>>> Do not write configuration data in probe(), we have config() for that.
>>>>>
>>>>> Then we should call config() in rmi_function_probe() to ensure that
>>>>> any platform data or device tree configuration settings get written
>>>>> to the device.
>>>
>>> Well, yes, we may elect to update device configuration in probe, but
>>> then we should not be doing that 2nd time in ->config(). We shoudl pick
>>> either one or another.
>>
>> But as the code currently stands, config() is only called when a
>> device reset is detected, not during initialization.  So if there's
>> platform specific configuration data that needs to be written to a
>> function, it won't get written until after a device reset occurs,
>> which might never happen.  So either we need to write that data (or
>> call config()) in each function's probe(), or in
>> rmi_function_probe().
>
> Ah, I missed the fact that we do not normally call ->config() unless
> device was reset. BTW, if device was reset, shouldn't we tear down
> everything and then reenumerate all functions?

That's only required if the reset is a result of the device being 
reflashed.  Since we're dropping support for user-space control of 
reflash, and will instead use an in-driver reflash, we know which resets 
are the result of a reflash and which aren't. The reflash code will do 
the following sequence:

- tell the core to tear down the functions
- perform the reflash operation
- reset the device
- tell the core to re-enumerate the functions


					Chris
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