linux-kernel - Re: [PATCH v6 4/7] drm/i915: Convert REG_GENMASK*() to fixed-width GENMASK

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Message-ID: <Z9rF5JFcEW2DOtcr@thinkpad>
Date: Wed, 19 Mar 2025 09:25:56 -0400
From: Yury Norov <yury.norov@...il.com>
To: Vincent Mailhol <mailhol.vincent@...adoo.fr>
Cc: Jani Nikula <jani.nikula@...ux.intel.com>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	Andi Shyti <andi.shyti@...ux.intel.com>,
	David Laight <David.Laight@...lab.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v6 4/7] drm/i915: Convert REG_GENMASK*() to fixed-width
 GENMASK_U*()

On Wed, Mar 19, 2025 at 01:37:32PM +0900, Vincent Mailhol wrote:
> On 19/03/2025 at 07:32, Jani Nikula wrote:
> > On Tue, 18 Mar 2025, Yury Norov <yury.norov@...il.com> wrote:
> >> On Sat, Mar 08, 2025 at 01:48:51AM +0900, Vincent Mailhol via B4 Relay wrote:
> >>> From: Lucas De Marchi <lucas.demarchi@...el.com>
> >>>
> >>> Now that include/linux/bits.h implements fixed-width GENMASK_U*(), use
> >>> them to implement the i915/xe specific macros. Converting each driver
> >>> to use the generic macros are left for later, when/if other
> >>> driver-specific macros are also generalized.
> >>>
> >>> Signed-off-by: Lucas De Marchi <lucas.demarchi@...el.com>
> >>> Acked-by: Jani Nikula <jani.nikula@...el.com>
> >>> Signed-off-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
> >>> ---
> >>> Changelog:
> >>>
> >>>   v5 -> v6:
> >>>
> >>>     - No changes.
> >>>
> >>>   v4 -> v5:
> >>>
> >>>     - Add braket to macro names in patch description,
> >>>       e.g. 'REG_GENMASK*' -> 'REG_GENMASK*()'
> >>>
> >>>   v3 -> v4:
> >>>
> >>>     - Remove the prefixes in macro parameters,
> >>>       e.g. 'REG_GENMASK(__high, __low)' -> 'REG_GENMASK(high, low)'
> >>> ---
> >>>  drivers/gpu/drm/i915/i915_reg_defs.h | 108 ++++-------------------------------
> >>>  1 file changed, 11 insertions(+), 97 deletions(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/i915/i915_reg_defs.h b/drivers/gpu/drm/i915/i915_reg_defs.h
> >>> index e251bcc0c89f5710125bc70f07851b2cb978c89c..39e5ed9511174b8757b9201bff735fa362651b34 100644
> >>> --- a/drivers/gpu/drm/i915/i915_reg_defs.h
> >>> +++ b/drivers/gpu/drm/i915/i915_reg_defs.h
> >>> @@ -9,76 +9,19 @@
> >>>  #include <linux/bitfield.h>
> >>>  #include <linux/bits.h>
> >>>  
> >>> -/**
> >>> - * REG_BIT() - Prepare a u32 bit value
> >>> - * @__n: 0-based bit number
> >>> - *
> >>> - * Local wrapper for BIT() to force u32, with compile time checks.
> >>> - *
> >>> - * @return: Value with bit @__n set.
> >>> +/*
> >>> + * Wrappers over the generic BIT_* and GENMASK_* implementations,
> >>> + * for compatibility reasons with previous implementation
> >>>   */
> >>> -#define REG_BIT(__n)							\
> >>> -	((u32)(BIT(__n) +						\
> >>> -	       BUILD_BUG_ON_ZERO(__is_constexpr(__n) &&		\
> >>> -				 ((__n) < 0 || (__n) > 31))))
> >>> +#define REG_GENMASK(high, low)		GENMASK_U32(high, low)
> >>> +#define REG_GENMASK64(high, low)	GENMASK_U64(high, low)
> >>> +#define REG_GENMASK16(high, low)	GENMASK_U16(high, low)
> >>> +#define REG_GENMASK8(high, low)		GENMASK_U8(high, low)
> >>
> >> Nit. Maybe just
> >>
> >>  #define REG_GENMASK		GENMASK_U32
> > 
> > Please just keep it as it is for clarity.
> 
> I also prefer when the argument is clearly displayed. It shows at first
> glance that this is a function-like macro and reminds of the correct
> order of the argument without having to look at the definitions in
> bits.h. It also allows for people to grep "#define REG_GENMASK(" in
> order to find the macro definition.
> 
> To be honest, I don't have a strong opinion either, but because Jani
> also prefers it this way, I will keep as-is.

Please go with the original version. It was just a minor nitpick.