[PATCH 3/3] dm: core: Default to using DEVRES outside of xPL

[Tom Rini]

On Fri, Dec 26, 2025 at 08:55:40PM +0100, Michael Nazzareno Trimarchi wrote:
> Hi
> 
> On Fri, Dec 26, 2025 at 7:57 PM Tom Rini <trini at konsulko.com> wrote:
> >
> > On Fri, Dec 26, 2025 at 07:28:43PM +0100, Michael Nazzareno Trimarchi wrote:
> > > Hi Tom
> > >
> > > On Fri, Dec 19, 2025 at 9:21 PM Tom Rini <trini at konsulko.com> wrote:
> > > >
> > > > The devm alloc functions that we have may follow the Linux kernel model
> > > > where allocations are (almost always) automatically free()'d. However,
> > > > quite often we don't enable, in full U-Boot, the corresponding automatic
> > > > free. This in turn leads to memory leaks. Rather than manually tracking
> > > > allocations and implementing frees, rework things so that we follow
> > > > expectations now and enable the DEVRES functionality to manage frees.
> > > >
> > > > This turns DEVRES from a prompted symbol to a symbol that must be
> > > > select'd, and we now remove our non-managed alloc/free functions from
> > > > outside of xPL builds.
> > [snip]
> > > > @@ -279,8 +280,8 @@ config DEVRES
> > > >           released whether initialization fails half-way or the device gets
> > > >           detached.
> > > >
> > > > -         If this option is disabled, devres functions fall back to
> > > > -         non-managed variants.  For example, devres_alloc() to kzalloc(),
> > > > +         This option is disabled in xPL phases anddevres functions fall back
> > >
> > > Fix this typo
> >
> > OK.
> >
> > [snip]
> > > Can you please in the commit message a concrete example on what this
> > > commit takes care of?
> > > In short expand here:
> > > " in full U-Boot, the corresponding automatic free. This in turn leads
> > > to memory leaks."
> >
> > Sure. So for example:
> > commit 00e1fed93c8c3e4c9037741ea1b70a9e693a6e65
> > Author: Francois Berder <fberder at outlook.fr>
> > Date:   Tue Nov 11 11:30:19 2025 +0100
> >
> >     firmware: ti_sci: Fix memory leaks in devm_ti_sci_get_of_resource
> >
> >     - Fix temp memory leak
> >     - Free memory during error handling
> >
> >     Signed-off-by: Francois Berder <fberder at outlook.fr>
> >
> > Is needed (I'd have to re-read the threads to see if in whole or in
> > part) because DEVRES is optional today. And barring
> > drivers/core/devres.c doesn't work the way it's documented and expected,
> > the normal unwind path will eventually say "Ah, and devm_kfree these
> > devm_kmalloc'd areas". This was part of either the discussion for that
> > patch, or another one of Francois' patches adding devm_kfree() calls to
> > devm_kmalloc()'d areas.
> 
> As far as I understand the devres_release_probe should then free the resources
> allocated to dm_device.

Right. And without DEVRES enabled we don't have this match between alloc
and free, which is unexpected by most users of devm_kmalloc/etc as that
path is not optional in the kernel.

-- 
Tom
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