Messages in this thread |  | | | Date | Sat, 9 Oct 2004 13:28:39 +0200 | | Subject | Re: video_usercopy() enforces change of VideoText IOCTLs since 2.6.8 | | From | (Michael Geng) |
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On Sat, Oct 09, 2004 at 11:28:01AM +0200, Gerd Knorr wrote: > > > /* Copy arguments into temp kernel buffer */ > > > switch (_IOC_DIR(cmd)) { > > > case _IOC_NONE: > > > - parg = NULL; > > > + parg = (void*)arg; > > > break; > > > > (the typecast is unneeded) > > > > Seems that with this change we are now sometimes passing a user pointer > > into (*func)(). And we're sometimes passing a kernel pointer, yes? > > Assuming that ioctls passing _pointers_ are declared correctly with _IO* > that shouldn't be the case: _IOC_DIR(cmd) == _IOC_NONE means _IO() > means no pointer passed in. > > > Are all the implementations of (*func)() handling that correctly? > > Hmm, it broke for videotext, checking ... > > Ok, you can drop it. The videotext ioctls (include/videotext.h) don't > use the _IO*() macros but pass around pointers anyway, thats bad. > > Michael, you'll have to fix the saa5246a driver. video_usercopy() will > not work for you because the videotext ioctls doesn't use the _IO() > macros. You have to do the userspace copying in the driver yourself.
I would prefer fixing the IOCTLs in include/linux/videotext.h. These definitions are older than the _IO macros in linux/ioctl.h AFAIK. So it is clear that they can't conform to that definition. I would prefer redefining them with respect to the arguments passed to the IOCTLs.
This would be a little step towards unifying the kernel. Implementing a private usercopy in saa5246a.c and saa5249.c would be the opposite.
The concept with the _IO() macros is good and helps preventing errors in the use of IOCTLs. So also the videotext drivers should use it.
Nevertheless there is one big disadvantage: The userspace programs have to be recompiled because they of course have to use the same IOCTL definitions.
Nevertheless, affected are only saa5246a.c and saa5249.c. I think that there are not many people left in the world using these drivers. So I think we can afford to make a break here.
Do you agree? If so then I will work out a patch.
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