linux-kernel - Re: [PATCH hotfix 6.11 v2 3/3] minmax: reduce min/max macro expansion in atomisp driver

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Message-ID: <bfd0243f-9159-4397-9f8a-e26372ce85a5@redhat.com>
Date: Wed, 11 Sep 2024 20:03:58 +0200
From: Hans de Goede <hdegoede@...hat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Richard Narron <richard@...zen.com>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Marcin Wojtas <marcin.s.wojtas@...il.com>,
 Russell King <linux@...linux.org.uk>, "David S . Miller"
 <davem@...emloft.net>, Arnd Bergmann <arnd@...nel.org>,
 Linus Torvalds <torvalds@...uxfoundation.org>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 linux-staging@...ts.linux.dev, linux-mm@...ck.org,
 Andrew Lunn <andrew@...n.ch>, Dan Carpenter <dan.carpenter@...aro.org>,
 stable@...r.kernel.org
Subject: Re: [PATCH hotfix 6.11 v2 3/3] minmax: reduce min/max macro expansion
 in atomisp driver

Hi,

On 9/11/24 7:51 PM, Lorenzo Stoakes wrote:
> Avoid unnecessary nested min()/max() which results in egregious macro
> expansion. Use clamp_t() as this introduces the least possible expansion.
> 
> Not doing so results in an impact on build times.
> 
> This resolves an issue with slackware 15.0 32-bit compilation as reported
> by Richard Narron.
> 
> Presumably the min/max fixups would be difficult to backport, this patch
> should be easier and fix's Richard's problem in 5.15.
> 
> Reported-by: Richard Narron <richard@...zen.com>
> Closes: https://lore.kernel.org/all/4a5321bd-b1f-1832-f0c-cea8694dc5aa@aaazen.com/
> Fixes: 867046cc7027 ("minmax: relax check to allow comparison between unsigned arguments and signed constants")
> Cc: stable@...r.kernel.org
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Thanks, patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Regards,

Hans

> ---
>  .../staging/media/atomisp/pci/sh_css_frac.h   | 26 ++++++++++++++-----
>  1 file changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/media/atomisp/pci/sh_css_frac.h b/drivers/staging/media/atomisp/pci/sh_css_frac.h
> index b90b5b330dfa..8ba65161f7a9 100644
> --- a/drivers/staging/media/atomisp/pci/sh_css_frac.h
> +++ b/drivers/staging/media/atomisp/pci/sh_css_frac.h
> @@ -32,12 +32,24 @@
>  #define uISP_VAL_MAX		      ((unsigned int)((1 << uISP_REG_BIT) - 1))
> 
>  /* a:fraction bits for 16bit precision, b:fraction bits for ISP precision */
> -#define sDIGIT_FITTING(v, a, b) \
> -	min_t(int, max_t(int, (((v) >> sSHIFT) >> max(sFRACTION_BITS_FITTING(a) - (b), 0)), \
> -	  sISP_VAL_MIN), sISP_VAL_MAX)
> -#define uDIGIT_FITTING(v, a, b) \
> -	min((unsigned int)max((unsigned)(((v) >> uSHIFT) \
> -	>> max((int)(uFRACTION_BITS_FITTING(a) - (b)), 0)), \
> -	  uISP_VAL_MIN), uISP_VAL_MAX)
> +static inline int sDIGIT_FITTING(int v, int a, int b)
> +{
> +	int fit_shift = sFRACTION_BITS_FITTING(a) - b;
> +
> +	v >>= sSHIFT;
> +	v >>= fit_shift > 0 ? fit_shift : 0;
> +
> +	return clamp_t(int, v, sISP_VAL_MIN, sISP_VAL_MAX);
> +}
> +
> +static inline unsigned int uDIGIT_FITTING(unsigned int v, int a, int b)
> +{
> +	int fit_shift = uFRACTION_BITS_FITTING(a) - b;
> +
> +	v >>= uSHIFT;
> +	v >>= fit_shift > 0 ? fit_shift : 0;
> +
> +	return clamp_t(unsigned int, v, uISP_VAL_MIN, uISP_VAL_MAX);
> +}
> 
>  #endif /* __SH_CSS_FRAC_H */
> --
> 2.46.0
>