[PATCH v9 08/12] device core: Introduce DMA range map, supplanting dma_pfn_offset

[Jim Quinlan]

On Wed, Jul 29, 2020 at 10:28 AM Rob Herring <robh+dt at kernel.org> wrote:
>
> On Wed, Jul 29, 2020 at 12:19 AM Christoph Hellwig <hch at lst.de> wrote:
> >
> > On Tue, Jul 28, 2020 at 02:24:51PM -0400, Jim Quinlan wrote:
> > > I started using devm_kcalloc() but at least two reviewers convinced me
> > > to just use kcalloc().  In addition, when I was using devm_kcalloc()
> > > it was awkward because 'dev' is not available to this function.
> > >
> > > It comes down to whether unbind/binding the device N times is actually
> > > a reasonable usage.  As for my experience I've seen two cases: (1) my
> > > overnight "bind/unbind the PCIe RC driver" script, and we have a
> > > customer who does an unbind/bind as a hail mary to bring back life to
> > > their dead EP device.  If the latter case happens repeatedly, there
> > > are bigger problems.
> >
> > We can't just leak the allocations.  Do you have a pointer to the
> > arguments against managed resources?  I'm generally not a huge fan
> > of the managed resources, but for a case like this they actually seem
> > useful.  If we don't use the managed resources we'll at leat need
> > to explicitly free the resources when freeing the device.
>
> The lifetime for devm_kcalloc may not be what we want here. devm
> allocs are freed on probe fail or remove, not on freeing the device
> (there is a just in case free there too though).

What do you suggest doing as an alternative?

Jim
>
>
> Rob