On Wed, Sep 16, 2026 at 11:36:25AM +0200, Ulf Hansson wrote:
On Wed, Sep 16, 2026 at 9:43 AM Johan Hovold johan@kernel.org wrote:
On Tue, Sep 15, 2026 at 03:20:46PM +0200, Ulf Hansson wrote:
From: Ulf Hansson ulfh@kernel.org
As there are no longer any users of these functions, let's make them internal to the mmc core.
Why would you want to do that? The devres helpers should just be simple wrappers around these and sometimes devres just isn't a good fit.
At the moment there seems to be no need for them. I would rather keep API/interfaces as simple as possible, so I prefer to remove them at this point.
If we see a need for them, we can always add them back.
Devres generally only works when all resources are device managed. Therefore you should always provide the underlying non-devres manages interface as well so that you don't force devres on drivers where it could cause trouble.
Especially with the work cancellations present in mmc_free_host() (which I have pointed out elsewhere should not be there), a driver may need to free the host before tearing down other non-devres managed resources during unbind.
Can you please point me to such an example so I can try to understand better?
We just discussed the renesas driver which can schedule rescan work before registering the host controller. [1]
If such a driver also has non-devres managed resources that are freed before the work is cancelled you have a use-after-free.
This may even be needed for greybus which currently destroys the connection before freeing the host.
I looked closer at gb_sdio_remove() (the greybus sdio driver's ->remove() callback) and I think the problem isn't about freeing the host.
Instead it seems like the call to mmc_remove_host() is done too late. To me it looks like when the mmc core tries to power off the card gracefully, through mmc_remove_host() the driver has already moved into a state where it no longer accepts any requests.
Yes, that looks wrong, but that's a separate issue.
I only pointed at greybus as an example of a driver which has non-devres managed resources. If there is (rescan) work still scheduled after probe() or remove() returns, there's a potential use-after-free.
Johan
[1] https://lore.kernel.org/lkml/ap7CaVj82BJZgjf6@hovoldconsulting.com/