From: Yury Norov <yury.norov@gmail.com>
To: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org
Subject: Re: Re: [PATCH 1/3] bits: introduce fixed-type genmasks
Date: Wed, 24 Jan 2024 07:27:58 -0800 [thread overview]
Message-ID: <ZbEsfl0tGLY+xJl0@yury-ThinkPad> (raw)
In-Reply-To: <gvkvihpcc45275idrfukjqbvgem767evrux5sx5lnh5hofqemk@ppbkcauitvwb>
On Wed, Jan 24, 2024 at 08:03:53AM -0600, Lucas De Marchi wrote:
> On Wed, Jan 24, 2024 at 09:58:26AM +0200, Jani Nikula wrote:
> > On Tue, 23 Jan 2024, Lucas De Marchi <lucas.demarchi@intel.com> wrote:
> > > From: Yury Norov <yury.norov@gmail.com>
> > >
> > > Generalize __GENMASK() to support different types, and implement
> > > fixed-types versions of GENMASK() based on it. The fixed-type version
> > > allows more strict checks to the min/max values accepted, which is
> > > useful for defining registers like implemented by i915 and xe drivers
> > > with their REG_GENMASK*() macros.
> >
> > Mmh, the commit message says the fixed-type version allows more strict
> > checks, but none are actually added. GENMASK_INPUT_CHECK() remains the
> > same.
> >
> > Compared to the i915 and xe versions, this is more lax now. You could
> > specify GENMASK_U32(63,32) without complaints.
>
> Doing this on top of the this series:
>
> -#define XELPDP_PORT_M2P_COMMAND_TYPE_MASK REG_GENMASK(30, 27)
> +#define XELPDP_PORT_M2P_COMMAND_TYPE_MASK REG_GENMASK(62, 32)
>
> and I do get a build failure:
>
> ../drivers/gpu/drm/i915/display/intel_cx0_phy.c: In function ‘__intel_cx0_read_once’:
> ../include/linux/bits.h:41:31: error: left shift count >= width of type [-Werror=shift-count-overflow]
> 41 | (((t)~0ULL - ((t)(1) << (l)) + 1) & \
> | ^~
I would better include this in commit message to avoid people's
confusion. If it comes to v2, can you please do it and mention that
this trick relies on shift-count-overflow compiler check?
Thanks,
Yury
next prev parent reply other threads:[~2024-01-24 15:28 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-24 5:02 [PATCH 0/3] Fixed-type GENMASK/BIT Lucas De Marchi
2024-01-24 5:02 ` [PATCH 1/3] bits: introduce fixed-type genmasks Lucas De Marchi
2024-01-24 7:58 ` Jani Nikula
2024-01-24 14:03 ` Lucas De Marchi
2024-01-24 15:27 ` Yury Norov [this message]
2024-01-24 15:49 ` Gustavo Sousa
2024-01-25 9:56 ` Jani Nikula
2024-01-29 14:49 ` Lucas De Marchi
2024-01-29 15:11 ` Yury Norov
2024-01-24 5:02 ` [PATCH 2/3] bits: Introduce fixed-type BIT Lucas De Marchi
2024-02-09 16:48 ` Yury Norov
2024-01-24 5:02 ` [PATCH 3/3] drm/i915: Convert REG_GENMASK* to fixed-width GENMASK_* Lucas De Marchi
2024-01-24 8:04 ` Jani Nikula
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