Re: linux-next: build failure after merge of the devsec-tsm tree

[Greg KH]

On Thu, May 08, 2025 at 05:37:41PM -0700, Dan Williams wrote:
> Stephen Rothwell wrote:
> > Hi all,
> > 
> > After merging the devsec-tsm tree, today's linux-next build (x86_64
> > allmodconfig) failed like this:
> > 
> > drivers/virt/coco/guest/tsm-mr.c: In function 'tsm_mr_create_attribute_group':
> > drivers/virt/coco/guest/tsm-mr.c:228:29: error: assignment to 'const struct bin_attribute * const*' from incompatible pointer type 'struct bin_attribute **' [-Wincompatible-pointer-types]
> >   228 |         ctx->agrp.bin_attrs = no_free_ptr(bas);
> >       |                             ^
> > 
> > Caused by commit
> > 
> >   29b07a7b8f41 ("tsm-mr: Add TVM Measurement Register support")
> > 
> > interacting with commit
> > 
> >   9bec944506fa ("sysfs: constify attribute_group::bin_attrs")
> > 
> > from the driver-core tree.
> > 
> > I have applied the following merge resolution for today (there must be
> > a better solution).
> 
> Indeed.
> 
> So it looks like while there are plenty of dynamic binary attribute
> creation users (see sysfs_bin_attr_init() callers). There are zero that
> attempt to assign dynamically allocated attributes to be registered by a
> static @groups.
> 
> The @groups publishing model is preferable because the lifetime rules
> are all handled by the driver core at device add/del time.
> 
> So, while there is still casting involved, I think a better solution is
> to make the allocation const and then cast for init ala incremental
> patch below. Cedric, if this looks ok to you I'll send out another
> partial-reroll to get this fixed up so the build breakage stays out of
> bisection runs.

Ick, yeah, that seems ok.

But what are these binary files for?  I looked in the documentation and
found this entry:
	/sys/devices/virtual/misc/tdx_guest/measurements/rtmr[0123]:sha384
is that these binary files?

Why is sysfs being used to expose binary "registers" and not done
through the ioctl api instead?  That's an internal kernel-computed
structure, not coming from the hardware, or am I mistaken?

thanks,

greg k-h