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From: Kalle Valo <kvalo@kernel.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Francesco Magliocca <franciman12@gmail.com>,
	Jeff Johnson <quic_jjohnson@quicinc.com>,
	ath10k@lists.infradead.org, rmanohar@qti.qualcomm.com,
	linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linuxfoundation.org>
Subject: Use of void pointer arithmetic?
Date: Thu, 24 Feb 2022 11:59:31 +0200	[thread overview]
Message-ID: <87fso8vb3w.fsf_-_@kernel.org> (raw)
In-Reply-To: <20220224075346.GL3943@kadam> (Dan Carpenter's message of "Thu, 24 Feb 2022 10:53:46 +0300")

(Changing subject, adding Linus and linux-kernel)

Dan Carpenter <dan.carpenter@oracle.com> writes:

> On Thu, Feb 24, 2022 at 09:34:31AM +0200, Kalle Valo wrote:
>> Francesco Magliocca <franciman12@gmail.com> writes:
>> 
>> > Hi, I picked (void*) to be conformant with the other examples in htt_rx.c
>> > For example at line 1431:
>> >>    rxd = HTT_RX_BUF_TO_RX_DESC(hw,
>> >>                    (void *)msdu->data - hw->rx_desc_ops->rx_desc_size);
>> >
>> > But for me it is ok. Maybe we should fix all the occurrences of this kind.
>> 
>> Yeah, it would be good to fix the void pointer arithmetic in a separate
>> patch. I have planning to enable -Wpointer-arith in my ath10k-check and
>> ath11k-check scripts, so patches are very welcome.
>
> Void * casts simplify a lot of code.  Less noise.  More readable.
> They're more accurate in a sense because it's not a u8 at all.  The
> kernel can't compile with other compilers besides GCC and Clang so why
> care about that the C standard hasn't caught up?
>
> What does -Wpointer-arith buy us?

A good question. I have always just thought we should avoid void pointer
arithmetic due to the C standard, but now that you mention it void
pointers can indeed simplify the code. So I'm not so sure anymore.

Any opinions? Is there a kernel wide recommendation for this?

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

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WARNING: multiple messages have this Message-ID (diff)
From: Kalle Valo <kvalo@kernel.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Francesco Magliocca <franciman12@gmail.com>,
	Jeff Johnson <quic_jjohnson@quicinc.com>,
	ath10k@lists.infradead.org, rmanohar@qti.qualcomm.com,
	linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linuxfoundation.org>
Subject: Use of void pointer arithmetic?
Date: Thu, 24 Feb 2022 11:59:31 +0200	[thread overview]
Message-ID: <87fso8vb3w.fsf_-_@kernel.org> (raw)
In-Reply-To: <20220224075346.GL3943@kadam> (Dan Carpenter's message of "Thu, 24 Feb 2022 10:53:46 +0300")

(Changing subject, adding Linus and linux-kernel)

Dan Carpenter <dan.carpenter@oracle.com> writes:

> On Thu, Feb 24, 2022 at 09:34:31AM +0200, Kalle Valo wrote:
>> Francesco Magliocca <franciman12@gmail.com> writes:
>> 
>> > Hi, I picked (void*) to be conformant with the other examples in htt_rx.c
>> > For example at line 1431:
>> >>    rxd = HTT_RX_BUF_TO_RX_DESC(hw,
>> >>                    (void *)msdu->data - hw->rx_desc_ops->rx_desc_size);
>> >
>> > But for me it is ok. Maybe we should fix all the occurrences of this kind.
>> 
>> Yeah, it would be good to fix the void pointer arithmetic in a separate
>> patch. I have planning to enable -Wpointer-arith in my ath10k-check and
>> ath11k-check scripts, so patches are very welcome.
>
> Void * casts simplify a lot of code.  Less noise.  More readable.
> They're more accurate in a sense because it's not a u8 at all.  The
> kernel can't compile with other compilers besides GCC and Clang so why
> care about that the C standard hasn't caught up?
>
> What does -Wpointer-arith buy us?

A good question. I have always just thought we should avoid void pointer
arithmetic due to the C standard, but now that you mention it void
pointers can indeed simplify the code. So I'm not so sure anymore.

Any opinions? Is there a kernel wide recommendation for this?

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

  reply	other threads:[~2022-02-24  9:59 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-21 12:26 [PATCH v2] ath10k: fix pointer arithmetic error in trace call Francesco Magliocca
2022-02-21 12:26 ` Francesco Magliocca
2022-02-22 20:52 ` Jeff Johnson
2022-02-22 20:52   ` Jeff Johnson
2022-02-23 11:48   ` Francesco Magliocca
2022-02-23 11:48     ` Francesco Magliocca
2022-02-24  7:34     ` Kalle Valo
2022-02-24  7:34       ` Kalle Valo
2022-02-24  7:53       ` Dan Carpenter
2022-02-24  7:53         ` Dan Carpenter
2022-02-24  9:59         ` Kalle Valo [this message]
2022-02-24  9:59           ` Use of void pointer arithmetic? Kalle Valo
2022-02-24 10:31           ` Johannes Berg
2022-02-24 10:31             ` Johannes Berg
2022-02-24 17:45           ` Linus Torvalds
2022-02-24 17:45             ` Linus Torvalds
2022-02-24  9:05 ` [PATCH v2] ath10k: fix pointer arithmetic error in trace call Kalle Valo
2022-02-24  9:05   ` Kalle Valo

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