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

[Hans Petter Selasky <hselasky@c2i.net>]

On Monday 23 May 2011 16:37:18 Andreas Oberritter wrote:
> On 05/23/2011 03:58 PM, Hans Petter Selasky wrote:
> > From be7d0f72ebf4d945cfb2a5c9cc871707f72e1e3c Mon Sep 17 00:00:00 2001
> > From: Hans Petter Selasky <hselasky@c2i.net>
> > Date: Mon, 23 May 2011 15:56:31 +0200
> > Subject: [PATCH] FE_GET_PROPERTY should be _IOW, because the associated
> > structure is transferred from userspace to kernelspace. Keep the old
> > ioctl around for compatibility so that existing code is not broken.
> 

Hi,

> Good catch, but I think _IOWR would be right, because the result gets
> copied from kernelspace to userspace.

Those flags are only for the IOCTL associated structure itself. The V4L DVB 
kernel only reads the dtv_properties structure in either case and does not 
write any data back to it. That's why only _IOW is required.

I checked somewhat and the R/W bits in the IOCTL command does not appear do be 
matched to the R/W permissions you have on the file handle? Or am I mistaken?

In other words the IOCTL R/W (_IOC_READ, _IOC_WRITE) bits should not reflect 
what the IOCTL actually does, like modifying indirect data?

> 
> It would be nice if you could send future patches inline rather than
> attached. I'd suggest using git format-patch and git send-email.

I will try to have a look at that. I'm waiting for the 16 patches I've 
submitted today to get reviewed and committed, before I start the next batch.

Thank you!

--HPS