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

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Message-ID: <6e5559f3-29b3-45d0-b475-cc021b90b1c2@t-8ch.de>
Date: Sat, 10 May 2025 09:05:52 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>, 
	sathyanarayanan.kuppuswamy@...ux.intel.com, yilun.xu@...el.com, sameo@...osinc.com, aik@....com, 
	suzuki.poulose@....com, steven.price@....com, lukas@...ner.de, Greg KH <greg@...ah.com>, 
	Cedric Xing <cedric.xing@...el.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, 
	Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: build failure after merge of the devsec-tsm tree

Hi Dan,

On 2025-05-08 17:37:41-0700, 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.

Take a look at nvmem_populate_sysfs_cells() in drivers/nvmem/core.c.
It uses an intermediary non-const pointer for the initialization and
works without any casts.

Could you then also use .bin_attrs_new?
.read_new and .write_new are already used.


Thomas