linux-kernel - Re: [alsa-devel] [PATCH v5 09/17] soundwire: intel: remove platform devices and use 'Master Devices' instead

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Date:   Fri, 10 Jan 2020 10:08:51 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     alsa-devel@...a-project.org, tiwai@...e.de,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        broonie@...nel.org, srinivas.kandagatla@...aro.org,
        jank@...ence.com, slawomir.blauciak@...el.com,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>
Subject: Re: [alsa-devel] [PATCH v5 09/17] soundwire: intel: remove platform
 devices and use 'Master Devices' instead


>>> The "big" difference is that probe is called by core (asoc) and not by
>>> driver onto themselves.. IMO that needs to go away.
>>
>> What I did is not different from what existed already with platform devices.
>> They were manually created, weren't they?
> 
> Manual creation of device based on a requirement is different, did I ask
> you why you are creating device :)
> 
> I am simple asking you not to call probe in the driver. If you need
> that, move it to core! We do not want these kind of things in the
> drivers...

What core are you talking about?

The SOF intel driver needs to create a device, which will then be bound 
with a SoundWire master driver.

What I am doing is no different from what your team did with 
platform_register_device, I am really lost on what you are asking.


>>>> FWIW, the implementation here follows what was suggested for Greybus 'Host
>>>> Devices' [1] [2], so it's not like I am creating any sort of dangerous
>>>> precedent.
>>>>
>>>> [1]
>>>> https://elixir.bootlin.com/linux/latest/source/drivers/greybus/es2.c#L1275
>>>> [2] https://elixir.bootlin.com/linux/latest/source/drivers/greybus/hd.c#L124
>>>
>>> And if you look closely all this work is done by core not by drivers!
>>> Drivers _should_ never do all this, it is the job of core to do that for
>>> you.
>>
>> Please look at the code again, you have a USB probe that will manually call
>> the GreyBus device creation.
>>
>> static int ap_probe(struct usb_interface *interface,
>> 		    const struct usb_device_id *id)
>> {
>> 	hd = gb_hd_create(&es2_driver, &udev->dev, 	
>>
>>
>> static struct usb_driver es2_ap_driver = {
>> 	.name =		"es2_ap_driver",
>> 	.probe =	ap_probe, <<< code above
>> 	.disconnect =	ap_disconnect,
>> 	.id_table =	id_table,
>> 	.soft_unbind =	1,
>> };
> 
> Look closely the driver es2 calls into greybus core hd.c and gets the
> work done, subtle but a big differances in the approaches..

I am sorry, I have absolutely no idea what you are referring to.

The code I copy/pasted here makes no call to the greybus core, it's 
ap_probe -> gb_hd_create. No core involved. If I am mistaken, please 
show me what I got wrong.