On Sat, Jun 13, 2020 at 01:33:16AM +1000, Greg Ungerer wrote:
> Hi Marc,
>
> On 12/6/20 5:48 pm, Marc Kleine-Budde wrote:
> > the k-build robot found this sparse problem, triggered by building a CAN
> > driver
> > for m68k. Is this a problem in our CAN driver or in the m68k headers?
>
> I suspect a problem with the m68k (specifically non-mmu) headers.
Indeed.
> 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?
> > > arch/m68k/include/asm/io_no.h:78:16: sparse: sparse: cast to
> > > restricted __le32
>
> This one I am not sure about yet.
> Still investigating.
swab32(__raw_readl(addr)) ?
Keeping __le32_to_cpu() will only force you to use ugly casts for no benefits
and the comment above explain clearly the situation about the endianness.
Best regards,
-- Luc
