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From: Nathan Chancellor <nathan@kernel.org>
To: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: linuxarm@huawei.com, mauro.chehab@huawei.com,
	Andrey Utkin <andrey_utkin@fastmail.com>,
	Anton Sviridenko <anton@corp.bluecherry.net>,
	Bluecherry Maintainers <maintainers@bluecherrydvr.com>,
	Ismael Luceno <ismael@iodev.co.uk>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
	llvm@lists.linux.dev
Subject: Re: [PATCH 08/20] media: solo6x10: add _maybe_unused to currently unused functions
Date: Fri, 26 Nov 2021 12:58:33 -0700	[thread overview]
Message-ID: <YaE8aRz1OIJ+x5P5@archlinux-ax161> (raw)
In-Reply-To: <18daa194878d8815beef39d6fed2a838e1c2cb68.1637781097.git.mchehab+huawei@kernel.org>

On Wed, Nov 24, 2021 at 08:13:11PM +0100, Mauro Carvalho Chehab wrote:
> There are several unused helper macros there, meant to parse some
> fields.
> 
> While there's not wrong with that, it generates clang warnings
> with W=1, causing build to break with CONFIG_WERROR.
> 
> So, add __maybe_unused to fix such warnings.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

I'll comment on this one patch but my opinion applies for all the
patches adding '__maybe_unused' to truly unused functions.

I agree with Laurent's comment [1]: unless this code is going to be used
soon, it should be deleted and resurrected when it is actually needed.
We have git for a reason and by adding this attribute, you are making it
harder to catch and eliminate unused functions, as no compiler will
catch them with an unused attribute (it is possible other static
analysis tools will but I doubt those are run as frequently as compilers
with W=1).

However, you are the maintainer so if you really want to keep these
around, I would recommend adding '__always_unused' instead of
'__maybe_unused' for documentation and auditing purposes, even though
they evaluate to the same thing:

$ rg __always_unused | wc -l
337

$ rg __maybe_unused | wc -l
4335

[1]: https://lore.kernel.org/r/YZtpnjPcGxVwhe61@pendragon.ideasonboard.com/

Cheers,
Nathan

> ---
> 
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH 00/20] at: https://lore.kernel.org/all/cover.1637781097.git.mchehab+huawei@kernel.org/
> 
>  drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c b/drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c
> index 0abcad4e84fa..85eaf5d00e9b 100644
> --- a/drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c
> +++ b/drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c
> @@ -391,12 +391,12 @@ static int solo_send_desc(struct solo_enc_dev *solo_enc, int skip,
>  }
>  
>  /* Extract values from VOP header - VE_STATUSxx */
> -static inline int vop_interlaced(const vop_header *vh)
> +static inline __maybe_unused int vop_interlaced(const vop_header *vh)
>  {
>  	return (__le32_to_cpu((*vh)[0]) >> 30) & 1;
>  }
>  
> -static inline u8 vop_channel(const vop_header *vh)
> +static inline __maybe_unused u8 vop_channel(const vop_header *vh)
>  {
>  	return (__le32_to_cpu((*vh)[0]) >> 24) & 0x1F;
>  }
> @@ -411,12 +411,12 @@ static inline u32 vop_mpeg_size(const vop_header *vh)
>  	return __le32_to_cpu((*vh)[0]) & 0xFFFFF;
>  }
>  
> -static inline u8 vop_hsize(const vop_header *vh)
> +static inline u8 __maybe_unused vop_hsize(const vop_header *vh)
>  {
>  	return (__le32_to_cpu((*vh)[1]) >> 8) & 0xFF;
>  }
>  
> -static inline u8 vop_vsize(const vop_header *vh)
> +static inline u8 __maybe_unused vop_vsize(const vop_header *vh)
>  {
>  	return __le32_to_cpu((*vh)[1]) & 0xFF;
>  }
> @@ -436,12 +436,12 @@ static inline u32 vop_jpeg_size(const vop_header *vh)
>  	return __le32_to_cpu((*vh)[4]) & 0xFFFFF;
>  }
>  
> -static inline u32 vop_sec(const vop_header *vh)
> +static inline u32 __maybe_unused vop_sec(const vop_header *vh)
>  {
>  	return __le32_to_cpu((*vh)[5]);
>  }
>  
> -static inline u32 vop_usec(const vop_header *vh)
> +static inline __maybe_unused u32 vop_usec(const vop_header *vh)
>  {
>  	return __le32_to_cpu((*vh)[6]);
>  }
> -- 
> 2.33.1
> 
> 

  parent reply	other threads:[~2021-11-26 20:00 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-24 19:13 [PATCH 00/20] Solve the remaining issues with clang and W=1 on media Mauro Carvalho Chehab
2021-11-24 19:13 ` [PATCH 01/20] media: adv7842: get rid of two unused functions Mauro Carvalho Chehab
2021-11-26 18:54   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 02/20] media: saa7134-go7007: get rid of to_state() function Mauro Carvalho Chehab
2021-11-26 18:55   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 03/20] media: davinci: get rid of an unused function Mauro Carvalho Chehab
2021-11-26 18:56   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 04/20] media: drxd: drop offset var from DownloadMicrocode() Mauro Carvalho Chehab
2021-11-26 18:57   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 05/20] media: drxk: drop operation_mode from set_dvbt() Mauro Carvalho Chehab
2021-11-26 19:02   ` Nathan Chancellor
2021-11-29  8:33     ` [PATCH v2 " Mauro Carvalho Chehab
2021-11-24 19:13 ` [PATCH 06/20] media: m88ds3103: drop reg11 calculus from m88ds3103b_select_mclk() Mauro Carvalho Chehab
2021-11-26 19:40   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 07/20] media: si21xx: report eventual errors at set_frontend Mauro Carvalho Chehab
2021-11-26 19:45   ` Nathan Chancellor
2021-11-29  8:40     ` Mauro Carvalho Chehab
2021-11-24 19:13 ` [PATCH 08/20] media: solo6x10: add _maybe_unused to currently unused functions Mauro Carvalho Chehab
2021-11-25 21:18   ` Ismael Luceno
2021-11-26 19:58   ` Nathan Chancellor [this message]
2021-11-29  8:44     ` Mauro Carvalho Chehab
2021-11-24 19:13 ` [PATCH 09/20] media: si470x: fix printk warnings with clang Mauro Carvalho Chehab
2021-11-26 20:13   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 10/20] media: radio-si476x: drop a container_of() abstraction macro Mauro Carvalho Chehab
2021-11-26 20:14   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 11/20] media: lmedm04: don't ignore errors when setting a filter Mauro Carvalho Chehab
2021-11-26 20:16   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 12/20] media: au0828-i2c: drop a duplicated function Mauro Carvalho Chehab
2021-11-26 20:22   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 13/20] media: adv7604 add _maybe_unused to currently unused functions Mauro Carvalho Chehab
2021-11-24 19:13 ` [PATCH 14/20] media: adv7511: drop " Mauro Carvalho Chehab
2021-11-26 20:27   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 15/20] media: imx290: mark read reg function as __maybe_unused Mauro Carvalho Chehab
2021-11-24 19:13 ` [PATCH 16/20] media: davinci: vpbe_osd: " Mauro Carvalho Chehab
2021-11-24 19:13 ` [PATCH 17/20] media: qcom: camss: " Mauro Carvalho Chehab
2021-11-25 10:58   ` Robert Foss
2021-11-24 19:13 ` [PATCH 18/20] media: mtk-mdp: address a clang warning Mauro Carvalho Chehab
2021-11-24 19:21   ` Arnd Bergmann
2021-11-24 19:13 ` [PATCH 19/20] media: cobalt: drop an unused variable Mauro Carvalho Chehab
2021-11-26 20:29   ` Nathan Chancellor
2021-11-24 19:13 ` [PATCH 20/20] media: mxl5005s: drop some dead code Mauro Carvalho Chehab
2021-11-26 20:30   ` Nathan Chancellor
2021-11-24 19:23 ` [PATCH 00/20] Solve the remaining issues with clang and W=1 on media Arnd Bergmann

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