linux-kernel - Re: [PATCH 01/11] mm/ioremap: change the return value of io[re|un]map

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Message-ID: <Yuvo9jWGL6VWStDO@li-4a3a4a4c-28e5-11b2-a85c-a8d192c6f089.ibm.com>
Date:   Thu, 4 Aug 2022 17:42:46 +0200
From:   Alexander Gordeev <agordeev@...ux.ibm.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, hch@...radead.org,
        wangkefeng.wang@...wei.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 01/11] mm/ioremap: change the return value of
 io[re|un]map_allowed

On Mon, Aug 01, 2022 at 10:40:19PM +0800, Baoquan He wrote:

Hi Baoquan,

> --- a/arch/arm64/mm/ioremap.c
> +++ b/arch/arm64/mm/ioremap.c
> @@ -3,19 +3,20 @@
>  #include <linux/mm.h>
>  #include <linux/io.h>
>  
> -bool ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot)
> +void __iomem *ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot)
>  {
>  	unsigned long last_addr = phys_addr + size - 1;
> +	int ret = -EINVAL;

If ret variable is really needed?

> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index 72974cb81343..d72eb310fb3c 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -967,26 +967,27 @@ static inline void iounmap(volatile void __iomem *addr)
>  /*
>   * Arch code can implement the following two hooks when using GENERIC_IOREMAP
>   * ioremap_allowed() return a bool,
> - *   - true means continue to remap
> - *   - false means skip remap and return directly
> + *   - IS_ERR means return an error
> + *   - NULL means continue to remap
> + *   - a non-NULL, non-IS_ERR pointer is returned directly

If ioremap_allowed() returns a valid pointer, then the function name
is not as precise anymore.

> @@ -28,8 +29,11 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size,
>  	phys_addr -= offset;
>  	size = PAGE_ALIGN(size + offset);
>  
> -	if (!ioremap_allowed(phys_addr, size, prot))
> +	base = ioremap_allowed(phys_addr, size, prot);
> +	if (IS_ERR(base))
>  		return NULL;
> +	else if (base)
> +		return base;

It is probably just me, but the base name bit misleading here.

> @@ -50,9 +54,9 @@ EXPORT_SYMBOL(ioremap_prot);
>  
>  void iounmap(volatile void __iomem *addr)
>  {
> -	void *vaddr = (void *)((unsigned long)addr & PAGE_MASK);
> +	void __iomem *vaddr = (void __iomem *)((unsigned long)addr & PAGE_MASK);
>  
> -	if (!iounmap_allowed(vaddr))
> +	if (iounmap_allowed(vaddr))

I guess, iounmap_allowed() should accept void __iomem *, not void *.
Then addr needs to be passed to iounmap_allowed() not vaddr.

>  		return;