Fan Ni wrote:
> On Mon, Apr 14, 2025 at 03:19:50PM +0100, Jonathan Cameron wrote:
> > On Sun, 13 Apr 2025 17:52:09 -0500
> > Ira Weiny <ira.we...@intel.com> wrote:
[snip]
> >
> > > +
> > > +static bool cxl_verify_dcd_cmds(struct cxl_memdev_state *mds, unsigned
> > > long *cmds_seen)
> >
> > It's not immediately obvious to me what the right behavior
> > from something called cxl_verify_dcd_cmds() is. A comment might help with
> > that.
> >
> > I think all it does right now is check if any bits are set. In my head
> > it was going to check that all bits needed for a useful implementation were
> > set. I did have to go check what a 'logical and' of a bitmap was defined as
> > because that bit of the bitmap_and() return value wasn't obvious to me
> > either!
>
> The code only checks if any DCD command (48xx) is supported, if any is
> set, it will set "dcd_supported".
> As you mentioned, it seems we should check all the related commands are
> supported, otherwise it is not valid implementation.
>
> Fan
> >
> >
> > > +{
> > > + DECLARE_BITMAP(all_cmds, CXL_DCD_ENABLED_MAX);
> > > + DECLARE_BITMAP(dst, CXL_DCD_ENABLED_MAX);
> > > +
> > > + bitmap_fill(all_cmds, CXL_DCD_ENABLED_MAX);
> > > + return bitmap_and(dst, cmds_seen, all_cmds, CXL_DCD_ENABLED_MAX);
Yea... so this should read:
...
bitmap_and(dst, cmds_seen, all_cmds, CXL_DCD_ENABLED_MAX);
return bitmap_equal(dst, all_cmds, CXL_DCD_ENABLED_MAX);
...
Of course if a device has set any of these commands true it better have
set them all. Otherwise the device is broken and it will fail in bad
ways.
But I agree with both of you that this is much better and explicit that
something went wrong. A dev_dbg() might be in order to debug such an
issue.
Ira
[snip]
