On Monday 05 November 2007, Johannes Stezenbach wrote:
> On Mon, Nov 05, 2007, Steven Toth wrote:
> > Johannes Stezenbach wrote:
> >>
> >> struct dvb_tuning_param p[3] = {
> >> { .id = MODULATION, .val = MOD_8VSB },
> >> { .id = FREQUENCY, .val = 591250000 },
> >> { .id = 0 }
> >> };
> >> ioctl(fd, DVB_TUNE, p);
> >
> >
> > You can't reliably pass in variably length arrays into the kernel, or none
> > of the other kernel wide drivers do, they need to be fixed length for
> > sanity reasons.
>
> Of course you can have variable length args to ioctl(). It's
> just that you can't let dvb_usercopy() do the work anymore but
> have to call copy_from_user() yourself, but I would favor a simple,
> generic API anytime over one with unnecessary, arbitrary
> limits, so IMHO it's worth the little extra effort.
>
> #define DVB_TUNE _IOC(_IOC_WRITE,'o',82,0)
>
> plus
>
>
> diff -r 1acfe4149714 linux/drivers/media/dvb/dvb-core/dvbdev.c
> --- a/linux/drivers/media/dvb/dvb-core/dvbdev.c Mon Nov 05 10:30:39
> 2007 -0200
> +++ b/linux/drivers/media/dvb/dvb-core/dvbdev.c Mon Nov 05 18:23:41
> 2007 +0100
> @@ -362,9 +362,11 @@ int dvb_usercopy(struct inode *inode, st
> case _IOC_READ: /* some v4l ioctls are marked wrong ... */
> case _IOC_WRITE:
> case (_IOC_WRITE | _IOC_READ):
> - if (_IOC_SIZE(cmd) <= sizeof(sbuf)) {
> + if (_IOC_SIZE(cmd) == 0)
> + parg = arg;
> + else if (_IOC_SIZE(cmd) <= sizeof(sbuf))
> parg = sbuf;
> - } else {
> + else {
> /* too big to allocate from stack */
> mbuf = kmalloc(_IOC_SIZE(cmd),GFP_KERNEL);
> if (NULL == mbuf)
>
> (untested)
>
> (BTW, the majority of ioctls don't encode the argument size, this
> feature was invented just a few years ago; see man ioctl_list)
>
> Or you could encode the lenght seperately like e.g.
> I2C_RDWR does with its struct i2c_rdwr_ioctl_data argument.
> It's a matter of taste, not sanity or security.
>
>
> > 1) I've made minor changes to dvb_core to interpret these messages and
> > handle the ioctl. No changes have been made to the frontend drivers.
> >
> > 2) Adding support for s2 _inside_ the kernel will mean adding a single
> > method to dvb_frontend_ops which allows the dvb_core to notify a new S2
> > driver. The goal here is to minimize these changes also. I haven't
> > demonstrated that code here, becuse I felt it was more important to show
> > the impact to the userland API/ABI, knowing that DVB-S2 and other advanced
> > types (including analog) would naturally fit well within this model.
> >
> > 3) This applies to all devs. I welcome all feedback, for sure the sytax
> > might need some cleanup, but please don't shoot the idea down when it's
> > only had 6-8 hours work of engineering behind it. It's proof of concept. It
> > doesn't contain any of Manu's code so I don't feel bound politically or
> > technically. I think given another 4-5 hours I could show the HVR4000
> > working, and demonstrate many of the userland signal/statistic API's.
> >
> > At this stage I'm looking for a "Yes, in principle we like the idea, but
> > show me how you do feature XYZ" from other devs. At which point I'll flush
> > out more code this would probably lead to an RFC for your approval.
>
>
> Seems like no one is interested.
>
>
> BTW, since every DVB-S2 demod is also a DVB-S demod, why does
> no one split the DVB-S parts of their driver for merging
> first? It would make the users happy as it would change the
> state from "card not supported" to "card works for 95% of existing
> transponders". (Dunno how this fits into this thread but...)
>
hi everybody,
what are we doing now?
imho we are discussing a new change to the dvb-s2 api again.
although i do like this ioctl approach for further enhancements of the api,
i must admit that things that are already done have to be done again.
iirc, there is a multiproto version of szap, vdr, ...
although, existing drivers e.g. stb0899 must be rewritten/patched to handle the
new iotcl.
at least i do not know what this will mean to the rework and test scenario,
on both sides. this means if we take multiproto from manu - what has steven got
to do,
and, if we take stevens approach, whats on manus side.
i would really appreciate to get a working compromise instead of starting this
api extension
all over again for the X time since Nov. 2005 when - iirc felix domke and me -
started the discussion.
"Yes, in principle I like the idea" but someday we must get an end to the
implementation and
merge it.
best regards
marcel
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