linux-kernel - Re: [PATCH 3/7] dmaengine: st_fdma: Add STMicroelectronics FDMA engine driver support

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Date:	Mon, 31 Aug 2015 10:44:40 +0200
From:	Maxime Coquelin <maxime.coquelin@...com>
To:	Paul Bolle <pebolle@...cali.nl>,
	Peter Griffin <peter.griffin@...aro.org>
CC:	<lee.jones@...aro.org>, <devicetree@...r.kernel.org>,
	<dmaengine@...r.kernel.org>, <ludovic.barre@...com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <srinivas.kandagatla@...il.com>,
	<patrice.chotard@...com>, <vinod.koul@...el.com>,
	<dan.j.williams@...el.com>
Subject: Re: [PATCH 3/7] dmaengine: st_fdma: Add STMicroelectronics FDMA
 engine driver support



On 08/31/2015 10:08 AM, Paul Bolle wrote:
> Hi Maxime,
>
> On ma, 2015-08-31 at 09:49 +0200, Maxime Coquelin wrote:
>> On 07/09/2015 10:17 AM, Paul Bolle wrote:
>>>>> +static int __exit st_fdma_remove(struct platform_device *pdev)
>>>>> +{
>>>>> +	struct st_fdma_dev *fdev = platform_get_drvdata(pdev);
>>>>> +
>>>>> +	wait_for_completion(&fdev->fw_ack);
>>>>> +
>>>>> +	st_fdma_clk_disable(fdev);
>>>>> +
>>>>> +	return 0;
>>>>> +}
>>> Since this driver is built-in only this means st_fdma_remove() can
>>> never be used, right?
>> It's not because a driver is built-in only that it does not need a
>> remove callback.
>> An instance can be probed/removed any time via driver's bind/unbind
>> SysFS entries.
>> Am I missing something?
> (This discussion is moot because Peter already stated that a new version
> will be modular.)
>
> It follows from the __exit tag that st_fdma_remove() should never be
> part of the kernel image (in this version of the patch), doesn't it?
Yes, you are right.
The remove callback is relevant, but without the __exit tag.
>
> (I don't know what happens in this situation if an unbind sysfs entry is
> used to remove a driver. I've never tried that.)
>
>
Not checked whether the function is omitted when built-in, but in any 
case, I thnk remove callbacks should not be tagged with __exit.

Regards,
Maxime


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