Re: [PATCH] x86/calgary: fix bitcast type warnings

[Mukesh Ojha]

On 3/30/2019 3:15 AM, Jann Horn wrote:
> On Fri, Mar 29, 2019 at 9:19 AM Mukesh Ojha <mojha@xxxxxxxxxxxxxx> wrote:
> > On 3/29/2019 4:29 AM, Jann Horn wrote:
> > > The sparse checker attempts to ensure that all conversions between
> > > fixed-endianness numbers and numbers with native endianness are explicit.
> > > However, the calgary code reads and writes big-endian numbers from/to IO
> > > memory using {read,write}{l,q}(), which return native-endian numbers.
> > >
> > > This could be addressed by putting __force casts all over the place, but
> > > that would kind of defeat the point of the warning. Instead, create new
> > > helpers {read,write}{l,q}_be() for big-endian IO that convert from/to
> > > native endianness.
> > >
> > > Most of this patch is a straightforward conversion; the following parts
> > > aren't just mechanical replacement:
> > >
> > >    - ->tar_val is now a native-endian number instead of big-endian
> > >    - calioc2_handle_quirks() did `cpu_to_be32(readl(target))` when it
> > >      intended to do `be32_to_cpu(readl(target))` (but that has no actual
> > >      effects outside of type warnings)
> > >
> > > This gets rid of 108 lines of sparse warnings.
> > >
> > > Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
> > > ---
> > > compile-tested only
> > >
> > >    arch/x86/kernel/pci-calgary_64.c | 108 ++++++++++++++++++-------------
> > >    1 file changed, 64 insertions(+), 44 deletions(-)
> > >
> > > diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
> > > index c70720f61a34..36cd66d940fb 100644
> > > --- a/arch/x86/kernel/pci-calgary_64.c
> > > +++ b/arch/x86/kernel/pci-calgary_64.c
> > > @@ -534,6 +534,26 @@ static inline int is_cal_pci_dev(unsigned short device)
> > >        return (is_calgary(device) || is_calioc2(device));
> > >    }
> >
> > Can the existing api's not be used here like iowrite64be/ioread64be/ or
> > similar variant in "include/asm-generic/io.h"
> Given what Logan said, I think it probably makes sense to keep the patch as-is?

Sure go ahead, will have a look at this patch one more time.