Linux CAN drivers development

* Re: [PATCH v3 00/27] kill devm_ioremap_nocache
From: Yisheng Xie @ 2017-12-25  1:34 UTC (permalink / raw)
  To: christophe leroy, Greg KH
  Cc: linux-mips, ulf.hansson, jakub.kicinski, platform-driver-x86,
	airlied, linux-wireless, linus.walleij, alsa-devel, dri-devel,
	linux-kernel, linux-ide, linux-mtd, daniel.vetter, dan.j.williams,
	jason, linux-rtc, boris.brezillon, mchehab, dmaengine, vinod.koul,
	richard, marek.vasut, industrypack-devel, linux-pci, dvhart,
	linux, linux-media, seanpaul, devel, linux-watchdog, arnd,
	b.zolnierkie, marc.zyngier, jslaby
In-Reply-To: <b8ff7f17-7f2c-f220-9833-7ae5bd7343d5@c-s.fr>


On 2017/12/24 17:05, christophe leroy wrote:
> 
> 
> Le 23/12/2017 à 14:48, Greg KH a écrit :
>> On Sat, Dec 23, 2017 at 06:55:25PM +0800, Yisheng Xie wrote:
>>> Hi all,
>>>
>>> When I tried to use devm_ioremap function and review related code, I found
>>> devm_ioremap and devm_ioremap_nocache is almost the same with each other,
>>> except one use ioremap while the other use ioremap_nocache.
>>
>> For all arches?  Really?  Look at MIPS, and x86, they have different
>> functions.
>>
>>> While ioremap's
>>> default function is ioremap_nocache, so devm_ioremap_nocache also have the
>>> same function with devm_ioremap, which can just be killed to reduce the size
>>> of devres.o(from 20304 bytes to 18992 bytes in my compile environment).
>>>
>>> I have posted two versions, which use macro instead of function for
>>> devm_ioremap_nocache[1] or devm_ioremap[2]. And Greg suggest me to kill
>>> devm_ioremap_nocache for no need to keep a macro around for the duplicate
>>> thing. So here comes v3 and please help to review.
>>
>> I don't think this can be done, what am I missing?  These functions are
>> not identical, sorry for missing that before.
> 
> devm_ioremap() and devm_ioremap_nocache() are quite similar, both use devm_ioremap_release() for the release, why not just defining:
> 
> static void __iomem *__devm_ioremap(struct device *dev, resource_size_t offset,
>                resource_size_t size, bool nocache)
> {
> [...]
>     if (nocache)
>         addr = ioremap_nocache(offset, size);
>     else
>         addr = ioremap(offset, size);
> [...]
> }
> 
> then in include/linux/io.h
> 
> static inline void __iomem *devm_ioremap(struct device *dev, resource_size_t offset,
>                resource_size_t size)
> {return __devm_ioremap(dev, offset, size, false);}
> 
> static inline void __iomem *devm_ioremap_nocache(struct device *dev, resource_size_t offset,
>                    resource_size_t size);
> {return __devm_ioremap(dev, offset, size, true);}

Yeah, this seems good to me, right now we have devm_ioremap, devm_ioremap_wc, devm_ioremap_nocache
May be we can use an enum like:
typedef enum {
	DEVM_IOREMAP = 0,
	DEVM_IOREMAP_NOCACHE,
	DEVM_IOREMAP_WC,
} devm_ioremap_type;

static inline void __iomem *devm_ioremap(struct device *dev, resource_size_t offset,
                resource_size_t size)
 {return __devm_ioremap(dev, offset, size, DEVM_IOREMAP);}

 static inline void __iomem *devm_ioremap_nocache(struct device *dev, resource_size_t offset,
                    resource_size_t size);
 {return __devm_ioremap(dev, offset, size, DEVM_IOREMAP_NOCACHE);}

 static inline void __iomem *devm_ioremap_wc(struct device *dev, resource_size_t offset,
                    resource_size_t size);
 {return __devm_ioremap(dev, offset, size, DEVM_IOREMAP_WC);}

 static void __iomem *__devm_ioremap(struct device *dev, resource_size_t offset,
                resource_size_t size, devm_ioremap_type type)
 {
     void __iomem **ptr, *addr = NULL;
 [...]
     switch (type){
     case DEVM_IOREMAP:
         addr = ioremap(offset, size);
         break;
     case DEVM_IOREMAP_NOCACHE:
         addr = ioremap_nocache(offset, size);
         break;
     case DEVM_IOREMAP_WC:
         addr = ioremap_wc(offset, size);
         break;
     }
 [...]
 }

Thanks
Yisheng

> 
> Christophe
> 
>>
>> thanks,
>>
>> greg k-h
>> -- 
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