linux-kernel - Re: [RFC PATCH v3 4/5] input: add onkey driver for Marvell 88PM886 PMIC

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Message-ID: <Ze4qx9KQEPU9U8JN@google.com>
Date: Sun, 10 Mar 2024 14:48:55 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Karel Balej <karelb@...li.ms.mff.cuni.cz>, Lee Jones <lee@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
	Duje Mihanović <duje.mihanovic@...le.hr>,
	~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org
Subject: Re: [RFC PATCH v3 4/5] input: add onkey driver for Marvell 88PM886
 PMIC

On Sun, Mar 10, 2024 at 09:35:36PM +0100, Krzysztof Kozlowski wrote:
> On 10/03/2024 12:35, Karel Balej wrote:
> > Dmitry Torokhov, 2024-03-04T17:10:59-08:00:
> >> On Mon, Mar 04, 2024 at 09:28:45PM +0100, Karel Balej wrote:
> >>> Dmitry,
> >>>
> >>> Dmitry Torokhov, 2024-03-03T12:39:46-08:00:
> >>>> On Sun, Mar 03, 2024 at 11:04:25AM +0100, Karel Balej wrote:
> >>>>> From: Karel Balej <balejk@...fyz.cz>
> >>>>>
> >>>>> Marvell 88PM886 PMIC provides onkey among other things. Add client
> >>>>> driver to handle it. The driver currently only provides a basic support
> >>>>> omitting additional functions found in the vendor version, such as long
> >>>>> onkey and GPIO integration.
> >>>>>
> >>>>> Signed-off-by: Karel Balej <balejk@...fyz.cz>
> >>>>> ---
> >>>>>
> >>>>> Notes:
> >>>>>     RFC v3:
> >>>>>     - Drop wakeup-source.
> >>>>>     RFC v2:
> >>>>>     - Address Dmitry's feedback:
> >>>>>       - Sort includes alphabetically.
> >>>>>       - Drop onkey->irq.
> >>>>>       - ret -> err in irq_handler and no initialization.
> >>>>>       - Break long lines and other formatting.
> >>>>>       - Do not clobber platform_get_irq error.
> >>>>>       - Do not set device parent manually.
> >>>>>       - Use input_set_capability.
> >>>>>       - Use the wakeup-source DT property.
> >>>>>       - Drop of_match_table.
> >>>>
> >>>> I only said that you should not be using of_match_ptr(), but you still
> >>>> need to have of_match_table set and have MODULE_DEVICE_TABLE() for the
> >>>> proper module loading support.
> >>>
> >>> I removed of_match_table because I no longer need compatible for this --
> >>> there are no device tree properties and the driver is being instantiated
> >>> by the MFD driver.
> >>>
> >>> Is the MODULE_DEVICE_TABLE() entry needed for the driver to probe when
> >>> compiled as module? If that is the case, given what I write above, am I
> >>> correct that MODULE_DEVICE_TABLE(platform,...) would be the right thing
> >>> to use here?
> >>
> >> Yes, if uevent generated for the device is "platform:<name>" then
> >> MODULE_DEVICE_TABLE(platform,...) will suffice. I am not sure how MFD
> >> sets it up (OF modalias or platform), but you should be able to check
> >> the format looking at the "uevent" attribute for your device in sysfs
> >> (/sys/devices/bus/platform/...). 
> > 
> > The uevent is indeed platform.
> > 
> > But since there is only one device, perhaps having a device table is
> > superfluous and using `MODULE_ALIAS("platform:88pm886-onkey")` is more
> > fitting?
> 
> Adding aliases for standard IDs and standard cases is almost never
> correct. If you need module alias, it means your ID table is wrong (or
> missing, which is usually wrong).
> 
> > 
> > Although I don't understand why this is even necessary when the driver
> > name is such and the module is registered using
> > `module_platform_driver`...
> 
> ID table and MODULE_DEVICE_TABLE() are necessary for modprobe to work.
> Just run `modinfo`.

MODULE_DEVICE_TABLE() and MODULE_ALIAS() reduce to the same thing, but I
agree that we should not try to be too clever and simply use the ID
table.

Thanks.

-- 
Dmitry