linux-kernel - Re: [RFC v0 7/8] Input: ims-pcu: use firmware

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Date:	Sat, 30 Jul 2016 14:42:41 +0200
From:	Arend van Spriel <arend.vanspriel@...adcom.com>
To:	Daniel Wagner <daniel.wagner@...-carit.de>,
	Bjorn Andersson <bjorn.andersson@...aro.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Daniel Wagner <wagi@...om.org>, Bastien Nocera <hadess@...ess.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Johannes Berg <johannes.berg@...el.com>,
	Kalle Valo <kvalo@...eaurora.org>,
	Ohad Ben-Cohen <ohad@...ery.com>, linux-input@...r.kernel.org,
	linux-kselftest@...r.kernel.org, linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: Re: [RFC v0 7/8] Input: ims-pcu: use firmware_stat instead of
 completion

+ Luis (again) ;-)

On 29-07-16 08:13, Daniel Wagner wrote:
> On 07/28/2016 09:01 PM, Bjorn Andersson wrote:
>> On Thu 28 Jul 11:33 PDT 2016, Dmitry Torokhov wrote:
>>
>>> On Thu, Jul 28, 2016 at 09:55:11AM +0200, Daniel Wagner wrote:
>>>> From: Daniel Wagner <daniel.wagner@...-carit.de>
>>>>
>> [..]
>>>
>>> Do not quite like it... I'd rather asynchronous request give out a
>>> firmware status pointer that could be used later on.

Excellent. Why not get rid of the callback function as well and have
fw_loading_wait() return result (0 = firmware available, < 0 = fail).
Just to confirm, you are proposing a new API function next to
request_firmware_nowait(), right?

>>>     pcu->fw_st = request_firmware_async(IMS_PCU_FIRMWARE_NAME,
>>> -                       pcu,
>>> -                       ims_pcu_process_async_firmware);
    +			    pcu);
>>>     if (IS_ERR(pcu->fw_st))
>>>         return PTR_ERR(pcu->fw_st);
>>>
>>>     ....
>>>
>>>     err = fw_loading_wait(pcu->fw_st);
	if (err)
		return err;

	fw = fwstat_get_firmware(pcu->fw_st);

Or whatever consistent prefix it is going to be.

>>>
>>
>> In the remoteproc case (patch 6) this would clean up the code, rather
>> than replacing the completion API 1 to 1. I like it!
> 
> IIRC most drivers do it the same way. So request_firmware_async() indeed
> would be good thing to have. Let me try that.

While the idea behind this series is a good one I am wondering about the
need for these drivers to use the asynchronous API. The historic reason
might be to avoid timeout caused by user-mode helper, but that may no
longer apply and these drivers could be better off using
request_firmware_direct().

There have been numerous discussions about the firmware API. Here most
recent one:

http://www.spinics.net/lists/linux-wireless/index.html#152755

Regards,
Arend

> Thanks for the excellent feedback.
> 
> cheers,
> daniel
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