On Mon, Mar 13, 2023 at 12:07:27PM -0700, Fenghua Yu wrote:
> Hi, Greg,
>
> On 3/13/23 11:29, Greg Kroah-Hartman wrote:
> > In the functions unbind_store() and bind_store(), a struct bus_type *
> > should be a const one, as the driver core bus functions used by this
> > variable are expecting the pointer to be constant, and these functions
> > do not modify the pointer at all.
> >
> > Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> > Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> > Cc: Vinod Koul <vkoul@xxxxxxxxxx>
> > Cc: dmaengine@xxxxxxxxxxxxxxx
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > ---
> > Note, this is a patch that is a prepatory cleanup as part of a larger
> > series of patches that is working on resolving some old driver core
> > design mistakes. It will build and apply cleanly on top of 6.3-rc2 on
> > its own, but I'd prefer if I could take it through my driver-core tree
> > so that the driver core changes can be taken through there for 6.4-rc1.
> >
> > drivers/dma/idxd/compat.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/dma/idxd/compat.c b/drivers/dma/idxd/compat.c
> > index 3df21615f888..5fd38d1b9d28 100644
> > --- a/drivers/dma/idxd/compat.c
> > +++ b/drivers/dma/idxd/compat.c
> > @@ -16,7 +16,7 @@ extern void device_driver_detach(struct device *dev);
> > static ssize_t unbind_store(struct device_driver *drv, const char *buf, size_t count)
> > {
> > - struct bus_type *bus = drv->bus;
> > + const struct bus_type *bus = drv->bus;
> > struct device *dev;
> > int rc = -ENODEV;
> > @@ -32,7 +32,7 @@ static DRIVER_ATTR_IGNORE_LOCKDEP(unbind, 0200, NULL, unbind_store);
> > static ssize_t bind_store(struct device_driver *drv, const char *buf, size_t count)
> > {
> > - struct bus_type *bus = drv->bus;
> > + const struct bus_type *bus = drv->bus;
> > struct device *dev;
> > struct device_driver *alt_drv = NULL;
> > int rc = -ENODEV;
>
> After applying this patch, warning is reported:
>
> drivers/dma/idxd/compat.c: In function ‘bind_store’:
> drivers/dma/idxd/compat.c:47:47: warning: passing argument 2 of
> ‘driver_find’ discards ‘const’ qualifier from pointer target type
> [-Wdiscarded-qualifiers]
> 47 | alt_drv = driver_find("idxd", bus);
> | ^~~
> In file included from ./include/linux/device.h:32,
> from drivers/dma/idxd/compat.c:6:
> ./include/linux/device/driver.h:129:59: note: expected ‘struct bus_type *’
> but argument is of type ‘const struct bus_type *’
> 129 | struct bus_type *bus);
> | ~~~~~~~~~~~~~~~~~^~~
>
> Should the "bus" parameter in driver_find() definition be changed to const
> as well to avoid the warning?
Oops, yes, it needs an earlier patch in this series, sorry, I didn't
call that out properly in the notes section of the patch.
So I can just take this through my tree if that's ok.
thanks,
greg k-h
