Re: [PATCH 18/18] ipu3: Add driver for dummy INT3472 ACPI device

On Sun, Dec 13, 2020 at 10:48:39PM +0000, Daniel Scally wrote:

On 01/12/2020 18:49, Andy Shevchenko wrote:

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+	table_entry = (struct gpiod_lookup)GPIO_LOOKUP_IDX(acpi_dev_name(adev),
+							   ares->data.gpio.pin_table[0],
+							   func, 0, GPIO_ACTIVE_HIGH);

You won't need this if you have regular INT3472 platform driver.
Simple call there _DSM to map resources to the type and use devm_gpiod_get on
consumer behalf. Thus, previous patch is not needed.

How does the consumer (the camera sensor) retrieve the GPIO though ? The
_DSM is in the PMIC device object, while the real consumer is the camera
sensor.

1. A GPIO proxy
2. A custom GPIO lookup tables
3. An fwnode passing to the sensor (via swnodes graph)

First may issue deferred probe, while second needs some ordering tricks I guess.
Third one should also provide an ACPI GPIO mapping table or so to make the
consumer rely on names rather than custom numbers.

Perhaps someone may propose other solutions.

Hi Andy

Sorry; some more clarification here if you have time please:

No problem, thanks for discussing this.

1. Do you mean here, register a new gpio_chip providing GPIOs to the
sensors, and just have the .set() callback for that function set the
corresponding line against the INT3472 device?

Yes. On one hand it should be a consumer (*gpiod_get*() family of APIs),
on the other it should be provider of known (artificial) GPIO chip.

2. I thought custom GPIO lookup tables was what I was doing, are you
referring to something else?

I think so, i.e. nothing else from high point of view.

3. I guess you mean something like of_find_gpio() and acpi_find_gpio()
here? As far as I can see there isn't currently a swnodes
equivalent...we could just pass it via reference of course but it would
mean the sensor drivers would all need to account for that.

Theoretically we may provide GPIOs as swnodes. In that case the consumer will
get them as usual But I think it may be too complicated / over engineered.

-- 
With Best Regards,
Andy Shevchenko