[PATCH 32/36] dmaengine: idxd: use const struct bus_type *

[PATCH 32/36] dmaengine: idxd: use const struct bus_type *

[Greg Kroah-Hartman]

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@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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;
-- 
2.39.2

Re: [PATCH 32/36] dmaengine: idxd: use const struct bus_type *

[Fenghua Yu]

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@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Vinod Koul <vkoul@kernel.org>
> Cc: dmaengine@vger.kernel.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
> 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?

Thanks.

-Fenghua

Re: [PATCH 32/36] dmaengine: idxd: use const struct bus_type *

[Greg Kroah-Hartman]

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@intel.com>
> > Cc: Dave Jiang <dave.jiang@intel.com>
> > Cc: Vinod Koul <vkoul@kernel.org>
> > Cc: dmaengine@vger.kernel.org
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > ---
> > 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

Re: [PATCH 32/36] dmaengine: idxd: use const struct bus_type *

[Fenghua Yu]

Hi, Greg,

On 3/16/23 03:16, Greg Kroah-Hartman wrote:
> 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@intel.com>
>>> Cc: Dave Jiang <dave.jiang@intel.com>
>>> Cc: Vinod Koul <vkoul@kernel.org>
>>> Cc: dmaengine@vger.kernel.org
>>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> ---
>>> 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.

Sure.

Acked-by: Fenghua Yu <fenghua.yu@intel.com>

Thanks.

-Fenghua

Re: [PATCH 32/36] dmaengine: idxd: use const struct bus_type *

[Vinod Koul]

On 13-03-23, 19:29, 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.

Acked-by: Vinod Koul <vkoul@kernel.org>

-- 
~Vinod

Re: [PATCH 32/36] dmaengine: idxd: use const struct bus_type *

[Dave Jiang]

On 3/13/23 11:29 AM, 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@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Vinod Koul <vkoul@kernel.org>
> Cc: dmaengine@vger.kernel.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Acked-by: Dave Jiang <dave.jiang@intel.com>

> ---
> 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;

Re: [PATCH 32/36] dmaengine: idxd: use const struct bus_type *

[Greg Kroah-Hartman]

On Thu, Mar 16, 2023 at 04:57:54PM -0700, Fenghua Yu wrote:
> Hi, Greg,
> 
> On 3/16/23 03:16, Greg Kroah-Hartman wrote:
> > 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@intel.com>
> > > > Cc: Dave Jiang <dave.jiang@intel.com>
> > > > Cc: Vinod Koul <vkoul@kernel.org>
> > > > Cc: dmaengine@vger.kernel.org
> > > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > > ---
> > > > 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.
> 
> Sure.
> 
> Acked-by: Fenghua Yu <fenghua.yu@intel.com>

Great, thanks for this, I've now queued up the series in my tree.

greg k-h