linux-kernel - Re: [PATCH v2 3/3] platform/chrome: cros_ec

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Date: Fri, 29 Mar 2024 09:37:30 +0800
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Pavan Holla <pholla@...omium.org>, abhishekpandit@...omium.org,
	bleung@...omium.org, chrome-platform@...ts.linux.dev,
	gregkh@...uxfoundation.org, groeck@...omium.org,
	heikki.krogerus@...ux.intel.com, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 3/3] platform/chrome: cros_ec_ucsi: Implement UCSI PDC
 driver

On Thu, Mar 28, 2024 at 01:16:36PM +0100, Krzysztof Kozlowski wrote:
> On 28/03/2024 10:57, Tzung-Bi Shih wrote:
> > By looking other use cases of mfd_add_hotplug_devices():
> > $ grep -R --files-with-matches mfd_add_hotplug_devices drivers/mfd/
> > drivers/mfd/dln2.c
> > drivers/mfd/cros_ec_dev.c
> > drivers/mfd/viperboard.c
> > 
> > They also have no ID tables and need MODULE_ALIAS().
> > - drivers/gpio/gpio-dln2.c
> > - drivers/i2c/busses/i2c-dln2.c
> > - drivers/spi/spi-dln2.c
> > - drivers/iio/adc/dln2-adc.c
> > - drivers/gpio/gpio-viperboard.c
> > - drivers/i2c/busses/i2c-viperboard.c
> > - drivers/iio/adc/viperboard_adc.c
> 
> So if there is a bug in some driver, you are allowed to add it? :) There
> is plenty of poor examples, so what I was suggesting to look for good
> examples. I agree that itself might be a tricky task.
> 
> > I'm not sure whether using the path results in:
> > - Lack of device ID table.
> > - Need MODULE_ALIAS().
> > in the platform device drivers.  And perhaps it relies on the fallback match?
> 
> Guys, think for a sec. If you are adding module alias being equivalent
> to platform ID table entry, then why you are not using the platform ID
> table entry in the first? That's the entire point.
> 
> So to repeat myself:
> If you need it, usually it means your device ID table is wrong (e.g.
> misses either entries or MODULE_DEVICE_TABLE()).
> 
> MODULE_ALIAS() is not a substitute for incomplete ID table.

Thanks.  I see.

Yet another example in: drivers/mfd/max8997.c and drivers/rtc/rtc-max8997.c.

We should be able to use a platform_device_id, MODULE_DEVICE_TABLE(), and
`.id_table` for matching.

If that works, I think we need to turn most MODULE_ALIAS() use cases in
drivers/platform/chrome/ to this way afterward.