linux-kernel - Re: drivers/net/can/kvaser_pciefd.c:801:17: sparse: sparse: cast removes address space '<asn:2>' of expression

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Date:   Sat, 13 Jun 2020 12:19:47 +1000
From:   Greg Ungerer <gerg@...ux-m68k.org>
To:     Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Cc:     Marc Kleine-Budde <mkl@...gutronix.de>,
        kernel test robot <lkp@...el.com>,
        Henning Colliander <henning.colliander@...dente.se>,
        kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Jimmy Assarsson <extja@...ser.com>,
        Christer Beskow <chbe@...ser.com>
Subject: Re: drivers/net/can/kvaser_pciefd.c:801:17: sparse: sparse: cast
 removes address space '<asn:2>' of expression


On 13/6/20 2:35 am, Luc Van Oostenryck wrote:
> On Sat, Jun 13, 2020 at 01:33:16AM +1000, Greg Ungerer wrote:
>> On 12/6/20 5:48 pm, Marc Kleine-Budde wrote:
>> I think this one is due to not forcing the volatile cast in __raw_write().
>> So this change will fix that:
>>
>> diff --git a/arch/m68k/include/asm/io_no.h b/arch/m68k/include/asm/io_no.h
>> index 0498192e1d98..1bc739f1f1ad 100644
>> --- a/arch/m68k/include/asm/io_no.h
>> +++ b/arch/m68k/include/asm/io_no.h
>> @@ -14,15 +14,15 @@
>>    * that behavior here first before we include asm-generic/io.h.
>>    */
>>   #define __raw_readb(addr) \
>> -    ({ unsigned char __v = (*(volatile unsigned char *) (addr)); __v; })
>> +    ({ u8 __v = (*(__force volatile u8 *) (addr)); __v; })
>>   #define __raw_readw(addr) \
>> -    ({ unsigned short __v = (*(volatile unsigned short *) (addr)); __v; })
>> +    ({ u16 __v = (*(__force volatile u16 *) (addr)); __v; })
>>   #define __raw_readl(addr) \
>> -    ({ unsigned int __v = (*(volatile unsigned int *) (addr)); __v; })
>> +    ({ u32 __v = (*(__force volatile u32 *) (addr)); __v; })
>> -#define __raw_writeb(b, addr) (void)((*(volatile unsigned char *) (addr)) = (b))
>> -#define __raw_writew(b, addr) (void)((*(volatile unsigned short *) (addr)) = (b))
>> -#define __raw_writel(b, addr) (void)((*(volatile unsigned int *) (addr)) = (b))
>> +#define __raw_writeb(b, addr) (void)((*(__force volatile u8 *) (addr)) = (b))
>> +#define __raw_writew(b, addr) (void)((*(__force volatile u16 *) (addr)) = (b))
>> +#define __raw_writel(b, addr) (void)((*(__force volatile u32 *) (addr)) = (b))
> 
> Look good to me but isn't easier to leave them undefined and include
> asm-generic/io.h?

Not so simple at the moment. Although juggling a few things around within
io_no.h will let you use the asm-generic functions it will now throw up
a _lot_ of warnings in many of the architecture files that pass int constant
addresses to the raw_* functions. That is on my todo list.

Regards
Greg