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Date: Fri, 24 Jun 2011 13:26:27 +0200
From: Hans Verkuil <hverkuil@...all.nl>
To: Mauro Carvalho Chehab <mchehab@...radead.org>
Cc: Jesper Juhl <jj@...osbits.net>,
LKML <linux-kernel@...r.kernel.org>, trivial@...nel.org,
linux-media@...r.kernel.org, ceph-devel@...r.kernel.org,
Sage Weil <sage@...dream.net>
Subject: Re: [RFC] Don't use linux/version.h anymore to indicate a per-driver version - Was: Re: [PATCH 03/37] Remove unneeded version.h includes from include/
On Friday, June 24, 2011 13:21:14 Mauro Carvalho Chehab wrote:
> Em 23-06-2011 18:58, Jesper Juhl escreveu:
> > It was pointed out by 'make versioncheck' that some includes of
> > linux/version.h were not needed in include/.
> > This patch removes them.
> >
> > Signed-off-by: Jesper Juhl <jj@...osbits.net>
> > ---
> > include/linux/ceph/messenger.h | 1 -
> > include/media/pwc-ioctl.h | 1 -
> > 2 files changed, 0 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
> > index 31d91a6..291aa6e 100644
> > --- a/include/linux/ceph/messenger.h
> > +++ b/include/linux/ceph/messenger.h
> > @@ -6,7 +6,6 @@
> > #include <linux/net.h>
> > #include <linux/radix-tree.h>
> > #include <linux/uio.h>
> > -#include <linux/version.h>
> > #include <linux/workqueue.h>
> >
> > #include "types.h"
> > diff --git a/include/media/pwc-ioctl.h b/include/media/pwc-ioctl.h
> > index 0f19779..1ed1e61 100644
> > --- a/include/media/pwc-ioctl.h
> > +++ b/include/media/pwc-ioctl.h
> > @@ -53,7 +53,6 @@
> > */
> >
> > #include <linux/types.h>
> > -#include <linux/version.h>
> >
> > /* Enumeration of image sizes */
> > #define PSZ_SQCIF 0x00
>
>
> The usage of version.h at the Linux media kernel is due to a V4L2 API requirement[1],
> where an ioctl query of VIDIOC_QUERYCAP type would return the driver version formatted
> with KERNEL_VERSION() macro.
>
> [1] http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-querycap.html
>
> While a few driver maintainers are careful enough to increment it on every new
> kernel version where the driver was touched, others simply keep it outdated.
>
> IMHO, it doesn't make much sense on having a per-driver version field: the V4L2 layer
> should be enough to abstract hardware differences, and to avoid userspace to have a per
> driver list of hacks. I don't think that the userspace applications are really using it.
Applications are certainly using it. I know this for a fact for the ivtv driver where
feature improvements are marked that way.
Without more research on how this is used I am not comfortable with this.
Regards,
Hans
> Module versions should just use the MODULE_VERSION() macro.
>
> So, IMO, the better would be to convert this field into a V4L2 API version field
> instead like the enclosed patch. Of course, this also means to change the V4L2 API
> Docbook. After that, we can cleanup all those linux/version.h code on all V4L drivers.
>
> The idea is that, every time we add something new at the V4L2 API, we'll increment it
> to match the current kernel version.
>
> On a quick look, all drivers, except by one uses versions <= KERNEL_VERSION(3, 0, 0).
> The only exception is the pwc driver, with version is KERNEL_VERSION(10, 0, 12). Due to
> a bug on it, it also reports its version as: "10.0.14" at module version. The version
> 10.0.12 is reported there since 2006, even having suffered a major change, due to the
> removal of the V4L1 API, on changeset 479567ce3af7b99d645a3c53b8ca2fc65e46efdc.
> So, I think it would be safe to change it to 3.0.0, as using the version here, in the favor
> of a greater good. We can keep the driver-specific version only at
>
> Comments?
>
> If others are ok with that, I'll prepare the changesets.
>
> Cheers,
> Mauro
>
>
> -
>
> [media] v4l2 core: Use a per-API version instead of a per driver version
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@...hat.com>
>
> diff --git a/drivers/media/video/v4l2-ioctl.c b/drivers/media/video/v4l2-ioctl.c
> index 213ba7d..d8fa571 100644
> --- a/drivers/media/video/v4l2-ioctl.c
> +++ b/drivers/media/video/v4l2-ioctl.c
> @@ -16,6 +16,7 @@
> #include <linux/slab.h>
> #include <linux/types.h>
> #include <linux/kernel.h>diff --git a/drivers/media/video/v4l2-ioctl.c b/drivers/media/video/v4l2-ioctl.c
> index 213ba7d..b19ad56 100644
> --- a/drivers/media/video/v4l2-ioctl.c
> +++ b/drivers/media/video/v4l2-ioctl.c
> @@ -16,6 +16,7 @@
> #include <linux/slab.h>
> #include <linux/types.h>
> #include <linux/kernel.h>
> +#include <linux/version.h>
>
> #include <linux/videodev2.h>
>
> @@ -27,6 +28,8 @@
> #include <media/v4l2-device.h>
> #include <media/v4l2-chip-ident.h>
>
> +#define V4L2_API_VERSION KERNEL_VERSION(3, 0, 0)
> +
> #define dbgarg(cmd, fmt, arg...) \
> do { \
> if (vfd->debug & V4L2_DEBUG_IOCTL_ARG) { \
> @@ -606,13 +609,16 @@ static long __video_do_ioctl(struct file *file,
> break;
>
> ret = ops->vidioc_querycap(file, fh, cap);
> - if (!ret)
> + if (!ret) {
> + cap->version = V4L2_API_VERSION;
> +
> dbgarg(cmd, "driver=%s, card=%s, bus=%s, "
> "version=0x%08x, "
> "capabilities=0x%08x\n",
> cap->driver, cap->card, cap->bus_info,
> cap->version,
> cap->capabilities);
> + }
> break;
> }
>
> --
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