Hi Geert,
Am 14.03.2018 um 21:30 schrieb Geert Uytterhoeven:
> Hi Michael,
>
> On Wed, Mar 14, 2018 at 9:23 AM, Michael Schmitz <schmitzmic@xxxxxxxxx> wrote:
>> thanks for the review - largely uncontroversial except for the volatile...
>
> The presence of volatile in drivers is always considered controversial ;-)
Yes indeed. I just hadn't looked at raw_io.h in ages (too many unhappy
memories), and didn't remember the __force volatile trick there.
>> Meaning writeb(val, reg) instead of reg = val?
>>
>> #define out_8(addr,b) (void)((*(__force volatile u8 *) (addr)) = (b))
>>
>> nicely hides the 'volatile' but suggests I also need to pass it a
>> pointer, so
>>
>> writeb((addr >> 24) & 0xff, &dregs->dma_addr)
>
> Yes, you have to pass it an (__iomem) pointer.
Thanks.
>> I'll have to compare the assembly generated by the two versions before I
>> dare test that, but I'll give that a try. Liberal use of wmb() did fix
>> the miscompile but that just looked too ugly.
>
> Using the macros should have the same effect due to the embedded volatile.
I tend to agree, but crashing elgar or trashing the SCSI filesystem
there isn't something I would like to risk (Adrian has been very
accommodating allowing me to test the driver there, but a reset tends to
be taking a few hours thanks to the time zone difference). So I'd rather
make sure nothing can go wrong.
Cheers,
Michael
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
>
