Re: [PATCH 0 of 9] videobuf fixes

[Mauro Carvalho Chehab <mchehab@infradead.org>]

> > The patch is wrong. 
> 
> The patch fixes the unsafe way vivi is doing multiple opens right now
> and I am uninterested in spending anymore time trying to fix up vivi
> right now.  If you could fix vivi up that would be great.  

If the issue is specific to to vivi, that's ok. I'm just wandering if the
changesets would break a driver for a real device.

Unfortunately, I couldn't test your patch on a real hardware. The hardware I use
here to test PCI boards is currently broken[1].

> > 	2) you can see a program with an userspace app and record the
> > 	stream with another app. Both xawtv and xdtv do this, when you
> > 	ask for record: They call mencoder, asking it to read from
> > 	/dev/video0. This way, you'll have the tv app reading, using
> > 	mmap() or overlay methods, while mencoder is calling read() to
> > 	receive the stream.
> 
> Yes, I know.  But, vivi has no permission control mechanism right now
> for differentiating between streaming file handles and control ones.

What the other drivers do is to implement a small code for this lock. You may
take a look on res_get(), for example, on cx88. 

Btw, we had this lock on past versions of vivi, but this were removed on this
changeset:

changeset:   6275:cba23263534b
user:        bphilips@suse.de <bphilips@suse.de>
date:        Thu Sep 27 20:55:17 2007 -0300
files:       linux/drivers/media/video/vivi.c
description:
V4L: vivi.c remove the "resource" locking

The "resource" locking in vivi isn't needed since
streamon/streamoff/read_stream do mutual exclusion using
q->reading/q->streaming.

Maybe we can just revert this changeset.

> > Yet, vivi should allow multiple open to allow "panel" applications, to
> > be compliant with V4L2 API.
> 
> Yes, but someone needs to add the code to support this in vivi.  And
> until someone does vivi can only support one open at a time without
> crashing.

This is a small regression, but I think it is OK for now.

[1] I tried to fix it during the weekend, without success. The Ethernet
interface is not working fine - most of the time, it doesn't send packets.
Also, with 2 PCI's inside, only one is working fine. If I plug 3 PCI devices,
all devices work badly. I tried to replace the power supply, but the troubles
still continue. I think I'll need to start saving some money to buy a newer
hardware :(

Cheers,
Mauro

--
video4linux-list mailing list
Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe
https://www.redhat.com/mailman/listinfo/video4linux-list