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

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

On 1/12/20 11:18 PM, Vinod Koul wrote:
> On 10-01-20, 10:08, Pierre-Louis Bossart wrote:
>>
>>>>> 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?
> 
> soundwire core ofcourse! IMO All that which goes into soundwire-bus-objs is
> considered as soundwire core part and rest are drivers intel, qc, so on!
This master code was added to the bus:   v
                                          v
soundwire-bus-objs := bus_type.o bus.o master.o slave.o mipi_disco.o 
stream.o
obj-$(CONFIG_SOUNDWIRE) += soundwire-bus.o

and the API is also part of the sdw.h include file. That seems to meet 
exactly what you describe above, no?

git grep sdw_master_device_add (reformatted output)

drivers/soundwire/intel_init.c:
md = sdw_master_device_add(&intel_sdw_driver,

drivers/soundwire/master.c:
*sdw_master_device_add(struct sdw_master_driver *driver,

drivers/soundwire/master.c:
EXPORT_SYMBOL_GPL(sdw_master_device_add);

include/linux/soundwire/sdw.h:
*sdw_master_device_add(struct sdw_master_driver *driver,

So, what exactly is the issue?

We are not 'calling the probe in the [Intel] driver' as you state it, we 
use a SoundWire core API which in turn will create a device. The device 
core takes care of calling the probe, see the master.c code which is NOT 
Intel-specific.

>>
>> 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.
> 
> Again repeating myself, you call an API to do that is absolutely fine,
> but we don't do that in drivers or open code these things
That is still quite unclear, what 'open-coding' are you referring to?

I am starting to wonder if you missed the addition of the master 
functionality in the previous patch:

[PATCH v5 08/17] soundwire: add initial definitions for sdw_master_device

What this patch 9 does is call the core-defined API and implement the 
intel-specific master driver.

> 
>>>>>> 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.
> 
> 1. es2_ap_driver is host controller driver
> 
> 2. gb_hd_create() is an API provided by greybus core!

same in my code...

> 
> es2 driver doesn't open code creation like you are doing in intel driver,
> it doesn't call probe on its own, greybus does that
> 
> This is very common pattern in linux kernel subsytems, drivers dont do
> these things, the respective subsystem core does that... see about es2
> driver and implementation of gb_hd_create(). See callers of
> platform_register_device() and its implementation.
> 
> I don't know how else I can explain this to you, is something wrong in
> how I conveyed this info or you... or something else, I dont know!!!
the new 'master' functionality is part of the bus code, so please 
clarify what you see as problematic for the partition.