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

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Message-ID: <6f3b0d7b-1ce7-aaf1-63c6-08a22dc77791@gmail.com>
Date:   Sun, 13 Dec 2020 22:48:39 +0000
From:   Daniel Scally <djrscally@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-media@...r.kernel.org, devel@...ica.org, rjw@...ysocki.net,
        lenb@...nel.org, gregkh@...uxfoundation.org,
        mika.westerberg@...ux.intel.com, linus.walleij@...aro.org,
        bgolaszewski@...libre.com, wsa@...nel.org, yong.zhi@...el.com,
        sakari.ailus@...ux.intel.com, bingbu.cao@...el.com,
        tian.shu.qiu@...el.com, mchehab@...nel.org, robert.moore@...el.com,
        erik.kaneda@...el.com, pmladek@...e.com, rostedt@...dmis.org,
        sergey.senozhatsky@...il.com, linux@...musvillemoes.dk,
        kieran.bingham+renesas@...asonboard.com, jacopo+renesas@...ndi.org,
        laurent.pinchart+renesas@...asonboard.com,
        jorhand@...ux.microsoft.com, kitakar@...il.com,
        heikki.krogerus@...ux.intel.com
Subject: Re: [PATCH 18/18] ipu3: Add driver for dummy INT3472 ACPI device

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

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