linux-kernel - Re: [RFC PATCH v3 9/9] ipu3-cio2: Add functionality allowing software_node connections to sensors on platforms designed for Windows

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Message-ID: <91258d01-7226-880f-1388-02b43a71e0e3@gmail.com>
Date:   Thu, 29 Oct 2020 22:36:43 +0000
From:   Dan Scally <djrscally@...il.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linus.walleij@...aro.org, prabhakar.mahadev-lad.rj@...renesas.com,
        heikki.krogerus@...ux.intel.com, dmitry.torokhov@...il.com,
        laurent.pinchart+renesas@...asonboard.com,
        kieran.bingham+renesas@...asonboard.com, jacopo+renesas@...ndi.org,
        robh@...nel.org, davem@...emloft.net, linux@...musvillemoes.dk,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        pmladek@...e.com, mchehab@...nel.org, tian.shu.qiu@...el.com,
        bingbu.cao@...el.com, sakari.ailus@...ux.intel.com,
        yong.zhi@...el.com, rafael@...nel.org, gregkh@...uxfoundation.org,
        kitakar@...il.com
Subject: Re: [RFC PATCH v3 9/9] ipu3-cio2: Add functionality allowing
 software_node connections to sensors on platforms designed for Windows

Hi both

On 29/10/2020 20:17, Laurent Pinchart wrote:
> Hi Andy,
>
> On Mon, Oct 26, 2020 at 06:05:49PM +0200, Andy Shevchenko wrote:
>> On Mon, Oct 26, 2020 at 08:20:14AM +0000, Dan Scally wrote:
>>> On 24/10/2020 23:36, Laurent Pinchart wrote:
>>>> On Sat, Oct 24, 2020 at 11:28:06PM +0100, Daniel Scally wrote:
>>>>> On 24/10/2020 10:37, Laurent Pinchart wrote:
>>>>>>>> I wonder if we could avoid depending on the I2C device being created by
>>>>>>>> getting the fwnode from adev, and setting ->secondary manually. adev
>>>>>>>> would need to be passed to get_acpi_ssdb_sensor_data() instead of dev.
>>>>>>> Let me try that; I initially wanted to do
>>>>>>> set_secondary_fwnode(&adev->dev, fwnode) to avoid depending on the I2C
>>>>>>> dev being created but it turns out &adev->dev isn't the same pointer. I
>>>>>>> shall try it and see.
>>>>> Actually, thinking on this further I think maybe we can't avoid that -
>>>>> it's not actually in this patch series but during assigning GPIO
>>>>> resources parsed from PMIC's ACPI node to the sensor, I'm using
>>>>> dev_name() on the i2c dev to pass to .dev_id member of gpiod_lookup_table
>>>> Any chance we can construct the I2C device name from the ACPI device,
>>>> the same way that the ACPI/I2C core does ? It may be a dead end, but if
>>>> we could avoid depending on the I2C device, I think it will make
>>>> initialization easier. I have a feeling that will be difficult though,
>>>> as we'll need the I2C bus number, which won't be readily available.
>>> OK yeah; the i2c core does indeed just prefix "i2c-" onto the acpi
>>> device name, so I will make this change too.
>> This is part of the I²C core and if you go this way, do not home grow the
>> functionality that doesn't belong here.
>>
>> Instead, export a helper function that will do it for you and for I²C core with
>> explanation why it's needed.
> Agreed, I was actually considering suggesting that. Hardcoding the same
> naming scheme in two places is asking for trouble, especially if we
> don't let the I2C maintainers know. It should be easy to do, not
> necessarily the highest priority task, but something that should be
> handled to get this merged.
Understood - I'll have a look at the best way to do this once I'm
through the current to do list