From: Andy Shevchenko <andriy.shevchenko@intel.com>
To: Dan Carpenter <dan.carpenter@linaro.org>
Cc: "Adrian Barnaś" <abarnas@google.com>,
"Hans de Goede" <hansg@kernel.org>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Sakari Ailus" <sakari.ailus@linux.intel.com>,
"Andy Shevchenko" <andy@kernel.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-staging@lists.linux.dev
Subject: Re: [RFC] staging: media: atomisp: Simplyfy masking bit logic
Date: Tue, 2 Sep 2025 12:54:28 +0300 [thread overview]
Message-ID: <aLa-1GPJDxpX-soG@smile.fi.intel.com> (raw)
In-Reply-To: <aLaypTjukJJloGuL@stanley.mountain>
On Tue, Sep 02, 2025 at 12:02:29PM +0300, Dan Carpenter wrote:
> On Tue, Sep 02, 2025 at 07:38:40AM +0000, Adrian Barnaś wrote:
...
> > static inline hive_uedge
> > inv_subword(hive_uedge w, unsigned int start, unsigned int end)
> > {
> > - return w & (~(((1ULL << (end - 1)) - 1) << 1 | 1) | ((1ULL << start) - 1));
> > + return w & (~__GENMASK_ULL(end-1, start));
> > }
>
> nit: white space. Add spaces. Remove parentheses.
>
> These are supposed to be opposites, right? Subword and inverse Subword.
> You could dress them up to make them look more opposite.
>
> return (w & __GENMASK_ULL(end - 1, start)) >> start;
> return w & ~__GENMASK_ULL(end - 1, start);
The problem is (and actually with the (end-1, start) above that it might
generate a really bad code on some CPUs, so I really, really prefer the way
when _at least_ one of the parameters is constant.
That said, using
GENMASK_ULL(end - 1, 0)
in both cases makes also them look more similar (and opposition comes on how
start is being used).
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2025-09-02 9:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-02 7:38 [RFC] staging: media: atomisp: Simplyfy masking bit logic Adrian Barnaś
2025-09-02 9:02 ` Dan Carpenter
2025-09-02 9:54 ` Andy Shevchenko [this message]
2025-09-02 10:12 ` Dan Carpenter
2025-09-02 13:10 ` Adrian Barnaś
2025-09-02 9:42 ` Andy Shevchenko
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