linux-kernel - Re: [PATCH 6/9] iio: imu: st_lsm6dsx: remove event

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Message-ID: <798a41fa-eda6-4f27-955c-82fdb61c2083@baylibre.com>
Date: Mon, 3 Nov 2025 08:53:44 -0600
From: David Lechner <dlechner@...libre.com>
To: Francesco Lavra <flavra@...libre.com>,
 Andy Shevchenko <andy.shevchenko@...il.com>,
 Jonathan Cameron <jic23@...nel.org>
Cc: Andy Shevchenko <andriy.shevchenko@...el.com>,
 Lorenzo Bianconi <lorenzo@...nel.org>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/9] iio: imu: st_lsm6dsx: remove event_threshold field
 from hw struct

On 11/3/25 3:34 AM, Francesco Lavra wrote:
> On Sun, 2025-11-02 at 15:45 +0200, Andy Shevchenko wrote:
>> On Sun, Nov 2, 2025 at 1:30 PM Jonathan Cameron <jic23@...nel.org> wrote:
>>> On Thu, 30 Oct 2025 15:49:37 +0200
>>> Andy Shevchenko <andriy.shevchenko@...el.com> wrote:
>>>> On Thu, Oct 30, 2025 at 12:10:08PM +0100, Francesco Lavra wrote:
>>>>> On Thu, 2025-10-30 at 10:01 +0200, Andy Shevchenko wrote:
>>>>>> On Thu, Oct 30, 2025 at 08:27:49AM +0100, Francesco Lavra wrote:
>>
>> ...
>>
>>>>>>> +       *val = (data & reg->mask) >> __ffs(reg->mask);
>>>>>>
>>>>>> Seems like yet another candidate for field_get() macro.
>>>>>
>>>>> FIELD_GET() can only be used with compile-time constant masks.
>>>>> And apparently this is the case with u8_get_bits() too, because you
>>>>> get a
>>>>> "bad bitfield mask" compiler error if you try to use u8_get_bits().
>>>>
>>>> We are talking about different things.
>>>> Here are the pointers to what I'm talking:
>>>>
>>>> - git grep -n -w 'field_get'
>>>> -
>>>> https://lore.kernel.org/linux-gpio/cover.1761588465.git.geert+renesas@glider.be/
>>>>
>>> True that it will be a usecase for that, but given plan is to merge
>>> that through
>>> a different tree in next merge window, it's not available for us yet. 
>>> Hence would
>>> be a follow up patch next cycle.
>>
>> Yes, but we can still define them here. Dunno either with #under or
>> under (namespaced) names, but still possible to use now.
> 
> OK, I will define an ST_LSM6DSX_FIELD_GET() macro.

The macro should be named exactly `field_get()`, otherwise we will
have to rename all of the callers later after the series adding it
to linux/bitfield.h is merged. And it should have an
`#undef field_get` just like the other patches that series. Then
later, we only need to remove the #undef and #def lines and not
change the rest of the code.