[PATCH] USB: legousbtower: use stream_open for stream semantics

[PATCH] USB: legousbtower: use stream_open for stream semantics

[mdshahid03]

From: Mohammad Shahid <mdshahid03@gmail.com>

The LEGO USB Tower driver uses nonseekable_open() in tower_open()
However, its read and write have stream semantics.

Use stream_open instead to mark the file as a stream and disable
unnecessary file position handling.

The issue is reported by stream_open.cocci script as potential
deadlock between read and write operation.

Signed-off-by: Mohammad Shahid <mdshahid03@gmail.com>
---
 drivers/usb/misc/legousbtower.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 18dd4115befb..b849bd0e9664 100644
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -313,7 +313,7 @@ static int tower_open(struct inode *inode, struct file *file)
 	struct tower_reset_reply reset_reply;
 	int result;
 
-	nonseekable_open(inode, file);
+	stream_open(inode, file);
 	subminor = iminor(inode);
 
 	interface = usb_find_interface(&tower_driver, subminor);
-- 
2.43.0

Re: [PATCH] USB: legousbtower: use stream_open for stream semantics

[mdshahid03]

Hi,

Could you please review patch and give your feedback,when time permits.

Thanks
Shahid.

On 2026-10-28 23:58 +0530, mdshahid03@gmail.com wrote:
> From: Mohammad Shahid <mdshahid03@gmail.com>
> 
> The LEGO USB Tower driver uses nonseekable_open() in tower_open()
> However, its read and write have stream semantics.
> 
> Use stream_open instead to mark the file as a stream and disable
> unnecessary file position handling.
> 
> The issue is reported by stream_open.cocci script as potential
> deadlock between read and write operation.
> 
> Signed-off-by: Mohammad Shahid <mdshahid03@gmail.com>
> ---
>  drivers/usb/misc/legousbtower.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
> index 18dd4115befb..b849bd0e9664 100644
> --- a/drivers/usb/misc/legousbtower.c
> +++ b/drivers/usb/misc/legousbtower.c
> @@ -313,7 +313,7 @@ static int tower_open(struct inode *inode, struct file *file)
>  	struct tower_reset_reply reset_reply;
>  	int result;
>  
> -	nonseekable_open(inode, file);
> +	stream_open(inode, file);
>  	subminor = iminor(inode);
>  
>  	interface = usb_find_interface(&tower_driver, subminor);
> -- 
> 2.43.0
> 
> 

Re: [PATCH] USB: legousbtower: use stream_open for stream semantics

[Greg KH]

On Tue, Nov 10, 2026 at 11:01:36PM +0530, mdshahid03@gmail.com wrote:
> Hi,
> 
> Could you please review patch and give your feedback,when time permits.
> 
> Thanks
> Shahid.
> 
> On 2026-10-28 23:58 +0530, mdshahid03@gmail.com wrote:
> > From: Mohammad Shahid <mdshahid03@gmail.com>
> > 
> > The LEGO USB Tower driver uses nonseekable_open() in tower_open()
> > However, its read and write have stream semantics.
> > 
> > Use stream_open instead to mark the file as a stream and disable
> > unnecessary file position handling.
> > 
> > The issue is reported by stream_open.cocci script as potential
> > deadlock between read and write operation.
> > 
> > Signed-off-by: Mohammad Shahid <mdshahid03@gmail.com>
> > ---
> >  drivers/usb/misc/legousbtower.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)

How was this tested?

Re: [PATCH] USB: legousbtower: use stream_open for stream semantics

[mdshahid03]

Hi Greg,

I did basic sanity ,I build driver and ran smatch after changes.

I don't have Lego USB HW to test it ,but there is similar changes
in Xyllibus ,that was sent by me and Eli(maintainer)has tested in HW.
According to Eli ,There is no regressions with stream_open().

Here is discussion:
https://lore.kernel.org/all/24af6daf-dbf3-5c47-beb7-077c4473ea7e@outbound.gmail.com/

Thanks
Shahid.

On 2026-11-10 13:21 -0500, Greg KH wrote:
> On Tue, Nov 10, 2026 at 11:01:36PM +0530, mdshahid03@gmail.com wrote:
> > Hi,
> > 
> > Could you please review patch and give your feedback,when time permits.
> > 
> > Thanks
> > Shahid.
> > 
> > On 2026-10-28 23:58 +0530, mdshahid03@gmail.com wrote:
> > > From: Mohammad Shahid <mdshahid03@gmail.com>
> > > 
> > > The LEGO USB Tower driver uses nonseekable_open() in tower_open()
> > > However, its read and write have stream semantics.
> > > 
> > > Use stream_open instead to mark the file as a stream and disable
> > > unnecessary file position handling.
> > > 
> > > The issue is reported by stream_open.cocci script as potential
> > > deadlock between read and write operation.
> > > 
> > > Signed-off-by: Mohammad Shahid <mdshahid03@gmail.com>
> > > ---
> > >  drivers/usb/misc/legousbtower.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> How was this tested?
> 
> 

Re: [PATCH] USB: legousbtower: use stream_open for stream semantics

[Greg KH]

On Wed, Nov 11, 2026 at 06:30:21PM +0530, mdshahid03@gmail.com wrote:
> Hi Greg,
> 
> I did basic sanity ,I build driver and ran smatch after changes.

So, no testing :)

> I don't have Lego USB HW to test it ,but there is similar changes
> in Xyllibus ,that was sent by me and Eli(maintainer)has tested in HW.
> According to Eli ,There is no regressions with stream_open().
> 
> Here is discussion:
> https://lore.kernel.org/all/24af6daf-dbf3-5c47-beb7-077c4473ea7e@outbound.gmail.com/

If you don't have this hardware, then there's no rush on this potential
change.

thanks,

greg k-h