linux-kernel - Re: [PATCH v4 04/10] dma-engine: sun4i: Add support for Allwinner suniv F1C100s

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Message-ID: <4a52cf8b-dd55-4bf8-8c37-29c07749bee0@prolan.hu>
Date: Sat, 2 Nov 2024 10:06:49 +0100
From: Csókás Bence <csokas.bence@...lan.hu>
To: Amit Singh Tomar <amitsinght@...vell.com>, <dmaengine@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-sunxi@...ts.linux.dev>
CC: Mesih Kilinc <mesihkilinc@...il.com>, Vinod Koul <vkoul@...nel.org>,
	Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec <jernej.skrabec@...il.com>,
	Samuel Holland <samuel@...lland.org>
Subject: Re: [PATCH v4 04/10] dma-engine: sun4i: Add support for Allwinner
 suniv F1C100s

On 2024. 10. 31. 20:05, Amit Singh Tomar wrote:
>>    #define SUN4I_DMA_CFG_SRC_ADDR_MODE(mode)    ((mode) << 5)
>>    #define SUN4I_DMA_CFG_SRC_DRQ_TYPE(type)    (type)
>> +#define SUNIV_DMA_CFG_DST_DATA_WIDTH(width)    ((width) << 24)
>> +#define SUNIV_DMA_CFG_SRC_DATA_WIDTH(width)    ((width) << 8)
> 
> nit: Are the extra parentheses around width truly necessary? They seem 
> to be used throughout the file.

It's macro safety. So for instance if someone writes 
~SUNIV_DMA_CFG_DST_DATA_WIDTH(1 + 2), which would expand to ~1 + 2 << 24 
it doesn't get mis-interpreted as (~1) + (2 << 24) for instance. So 
yeah, I sure hope that _all code_ that has macros with parameters did 
not forget to wrap everything in parentheses, and not just "throughout 
[this] file".

Bence