[alsa-devel] [RFC 0/4] clk/driver: platform: Fix kfree() of const memory on setting driver_override

[Krzysztof Kozlowski]

On Mon, 18 Feb 2019 at 11:40, Geert Uytterhoeven <geert at linux-m68k.org> wrote:
>
> Hi Krzysztof,
>
> On Mon, Feb 18, 2019 at 11:27 AM Krzysztof Kozlowski <krzk at kernel.org> wrote:
> > The problem
> > ===========
> > Several device types (platform, amba, spi etc.) provide a driver_override
> > field.  On sysfs store or during device removal, they kfree() the
> > existing value.
> >
> > However the users are unaware of this and set the driver_override like:
> >
> >         pdev->driver_override = "exynos5-subcmu";
> >
> > which obviously leads to error.
>
> IMHO driver_override is not meant to be set by a driver, only from userspace,
> for binding the device to vfio (is there another use case?).
>
> >   clk: samsung: exynos5: Fix kfree() of const memory on setting
> >     driver_override
> >   slimbus: ngd: Fix kfree() of const memory on setting driver_override
>
> I see all users set override immediately after allocating a platform device.
> Can't they just allocate a platform device using the override name instead?
> What am I missing?

For the clk-exynos5-subcmu.c case, driver registers several
sub-devices. Each sub-devices is a clock controller associated with
power domain. I guess the author wanted to have meaningful names of
these sub-devices (DISP, CAM etc. like names of power domains),
instead of just exynos5-subcmu.1, exynos5-subcmu.2 ...

If driver_override should not be used for such case, then I could
replace it with what you said.

For the other uses of driver_override (drivers/rpmsg/rpmsg_internal.h
and drivers/slimbus/qcom-ngd-ctrl.c) I don't know.

Best regards,
Krzysztof