Message-ID: <4886676.atdPhlSkOF@phil>
Date: Wed, 27 Aug 2025 09:22:04 +0200
From: Heiko Stuebner <heiko@...ech.de>
To: Yury Norov <yury.norov@...il.com>,
 Rasmus Villemoes <linux@...musvillemoes.dk>,
 Jaehoon Chung <jh80.chung@...sung.com>, Ulf Hansson <ulf.hansson@...aro.org>,
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Cc: kernel@...labora.com, linux-kernel@...r.kernel.org,
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 Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
Subject:
 Re: [PATCH v3 07/20] drm/rockchip: dsi: switch to FIELD_PREP_WM16* macros

Am Montag, 25. August 2025, 10:28:27 Mitteleuropäische Sommerzeit schrieb Nicolas Frattaroli:
> The era of hand-rolled HIWORD_UPDATE macros is over, at least for those
> drivers that use constant masks.
> 
> Remove this driver's HIWORD_UPDATE macro, and replace instances of it
> with either FIELD_PREP_WM16 or FIELD_PREP_WM16_CONST, depending on
> whether they're in an initializer. This gives us better error checking,
> which already saved me some trouble during this refactor.
> 
> The driver's HIWORD_UPDATE macro doesn't shift up the value, but expects
> a pre-shifted value. Meanwhile, FIELD_PREP_WM16 and
> FIELD_PREP_WM16_CONST will shift the value for us, based on the given
> mask. So a few things that used to be a HIWORD_UPDATE(VERY_LONG_FOO,
> VERY_LONG_FOO) are now a somewhat more pleasant
> FIELD_PREP_WM16(VERY_LONG_FOO, 1).
> 
> There are some non-trivial refactors here. A few literals needed a UL
> suffix added to stop them from unintentionally overflowing as a signed
> long. To make sure all of these cases are caught, and not just the ones
> where the FIELD_PREP_WM16* macros use such a value as a mask, just mark
> every literal that's used as a mask as unsigned.
> 
> Non-contiguous masks also have to be split into multiple
> FIELD_PREP_WM16* instances, as the macro's checks and shifting logic
> rely on contiguous masks.
> 
> This is compile-tested only.
> 
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>

Reviewed-by: Heiko Stuebner <heiko@...ech.de>

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