On Mon, Oct 1, 2018 at 6:17 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
>
> On Mon, Oct 1, 2018 at 1:37 PM <sunil.kovvuri@xxxxxxxxx> wrote:
>
> > +/* Response to cmd ID as CGX_CMD_GET_FW_VER with cmd status as
> > + * CGX_STAT_SUCCESS
> > + */
> > +struct cgx_ver_s {
> > +#if defined(__BIG_ENDIAN_BITFIELD)
> > + uint64_t reserved2:47;
> > + uint64_t minor_ver:4;
> > + uint64_t major_ver:4;
> > + uint64_t reserved1:9;
> > +#else
> > + uint64_t reserved1:9;
> > + uint64_t major_ver:4;
> > + uint64_t minor_ver:4;
> > + uint64_t reserved2:47;
> > +#endif
> > +};
>
> This is not exactly what I meant in my comment. I think this may work
> correctly on all architectures that we support in Linux, but my point
> was that the layout of bit fields within a structure is completely up
> to the implementation, so it's really better to just avoid it entirely.
>
> Note that the data is being read with a call like
>
> ereg.val = cgx_read(cgx, lmac->lmac_id, CGX_EVENT_REG);
>
> which in turn is implemented using readq(), and that already
> performs a byte swap in order to do the right thing on big-endian
> architectures. The non-reserved bitfields in the two structures
> above span byte boundaries, so I can't even wrap my head around
> where the respective bits are supposed to be for all combinations
> of __BIG_ENDIAN/__LITTLE_ENDIAN and __BIG_ENDIAN_BITFIELD/
> __LITTLE_ENDIAN_BITFIELD.
>
> Arnd
Hi Arnd,
Thanks for your patience in checking patches and giving us feedback.
I have submitted v6 removing bitfields and using BITMASKs to extract fields.
Regards,
Sunil.
