Re: [PATCH] FE_GET_PROPERTY should be _IOW, because the associatedstructure is transferred from userspace to kernelspace. Keep the old ioctlaround for compatibility so that existing code is not broken.

From: Andreas Oberritter
Date: Fri Jun 03 2011 - 08:44:50 EST

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In reply to: Mauro Carvalho Chehab: "Re: [PATCH] FE_GET_PROPERTY should be _IOW, because the associatedstructure is transferred from userspace to kernelspace. Keep the old ioctlaround for compatibility so that existing code is not broken."
Next in thread: Mauro Carvalho Chehab: "Re: [PATCH] FE_GET_PROPERTY should be _IOW, because the associatedstructure is transferred from userspace to kernelspace. Keep the old ioctlaround for compatibility so that existing code is not broken."
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On 06/01/2011 11:15 PM, Mauro Carvalho Chehab wrote:
> The dvb_usercopy will do the right thing, if we use _IOR or _IORW.

It only works, because _IOC_READ triggers a copy_from_user, as a
workaround for wrongly marked ioctls like this, according to a code
comment. It does not really do the right thing, because in this special
case the later call to copy_to_user isn't required. But it doesn't do
any real harm either.

> I prefer to not apply this patch, as it won't fix anything. Adding an _OLD means
> that we'll need later to remove it, causing a regression. Ok, we may do like we did
> with V4L _OLD ioctl's that were marked as _OLD at 2.6.5 and were removed on a late
> 2.6.3x.

Either way is fine for me.

Regards,
Andreas
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