linux-kernel - Re: [PATCH v3 03/11] mm/ioremap: change the return value of io[re|un]map

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Date:   Sun, 9 Oct 2022 19:13:52 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Baoquan He <bhe@...hat.com>, <linux-kernel@...r.kernel.org>
CC:     <linux-mm@...ck.org>, <akpm@...ux-foundation.org>,
        <hch@...radead.org>, <agordeev@...ux.ibm.com>,
        <christophe.leroy@...roup.eu>, <schnelle@...ux.ibm.com>,
        <David.Laight@...LAB.COM>, <shorne@...il.com>,
        "Arnd Bergmann" <arnd@...db.de>, <linux-arch@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 03/11] mm/ioremap: change the return value of
 io[re|un]map_allowed and rename


On 2022/10/9 18:31, Baoquan He wrote:
> Currently, hooks ioremap_allowed() and iounmap_allowed() are used to
> check if it's qualified to do ioremap, and now this is done on ARM64.
> However, in oder to convert more architectures to take GENERIC_IOREMAP
> method, several more things need be done in those two hooks:
>   1) The io address mapping need be handled specifically on architectures,
>      e.g arc, ia64, s390;
>   2) The original physical address passed into ioremap_prot() need be
>      fixed up, e.g arc;
>   3) The 'prot' passed into ioremap_prot() need be adjusted, e.g on arc
>      and xtensa.
>
> To handle these three issues,
>
>   1) Rename ioremap_allowed() and iounmap_allowed() to arch_ioremap()
>      and arch_iounmap() since the old name can't reflect their
>      functionality after change;
>   2) Change the return value of arch_ioremap() so that arch can add
>      specifical io address mapping handling inside and return the maped
>      address. Now their returned value means:
>      ===
>      arch_ioremap() return a bool,
pointer?
>        - IS_ERR means return an error
>        - 0 means continue to remap
>        - a non-zero, non-IS_ERR pointer is returned directly
>      arch_iounmap() return a bool,
>        - true means continue to vunmap
>        - false means skip vunmap and return directly
...
>   /*
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index a68f8fbf423b..2ae16906f3be 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -1049,25 +1049,26 @@ 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
> - * iounmap_allowed() return a bool,
> + * arch_ioremap() return a bool,
ditto...
>   	area = get_vm_area_caller(size, VM_IOREMAP,
>   			__builtin_return_address(0));
>   	if (!area)
> @@ -52,7 +57,7 @@ void iounmap(volatile void __iomem *addr)
>   {
>   	void *vaddr = (void *)((unsigned long)addr & PAGE_MASK);
>   
> -	if (!iounmap_allowed(vaddr))
> +	if (!arch_iounmap((void __iomem *)addr))
vaddr?
>   		return;
>   
>   	if (is_vmalloc_addr(vaddr))