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
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