Re: [PATCH RESEND 0/7] Introduce MEDIA_VERSION to end KENREL_VERSION abuse in media

[Johannes Thumshirn]

On Thu, Jun 29, 2017 at 10:01:05AM -0700, Stephen Hemminger wrote:
> If you read Linus's comments on version.
> Driver version is meaningless and there is a desire to rip it out of all
> drivers. The reason is that drivers must always behave the same, i.e you
> can't use version to change API/ABI behavior. 

Indeed this causes more harm than good. We had support calls regarding the
mlx4 driver because of not incremented MODLE_VERSION()s. If we follow your
and Linus' path we shouldn't just get rid of the KERNEL_VERSION() usage
in media and replace it with a new version, but kill all the versioning
stuff out of media (and others) except for maybe the HW version.

> Any upstream driver should never use KERNEL_VERSION().

Exactly my reasoning.

-- 
Johannes Thumshirn  Storage
jthumsh...@suse.de+49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
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Re: [PATCH RESEND 0/7] Introduce MEDIA_VERSION to end KENREL_VERSION abuse in media

[Stephen Hemminger]

On Thu, 29 Jun 2017 11:42:59 +0200
Johannes Thumshirn  wrote:

> On Sat, Jun 24, 2017 at 05:15:07PM -0300, Mauro Carvalho Chehab wrote:
> > Sorry, but I can't see any advantage on it. On the downside, it
> > includes the media controller header file (media.h) where it
> > is not needed.  
> 
> My reasoning was the differences in semantics. KERNEL_VERSION() is for
> encoding the kernel's version triplet not a API or Hardware or whatever
> version. Other subsystems do this as well, for instance in NVMe we have the
> NVME_VS() macro which is used to encode the NVMe Spec compliance from a human
> readable form to the hardware's u32. Also KERNEL_VERISON() shouldn't have
> in-tree users IMHO. Yes there is _one_ other user of it in-tree which is EXT4
> and I already talked to Jan Kara about it and we decided to leave it in until
> 4.20.
> 
> Byte,
>   Johannes

If you read Linus's comments on version.
Driver version is meaningless and there is a desire to rip it out of all
drivers. The reason is that drivers must always behave the same, i.e you
can't use version to change API/ABI behavior. 

Any upstream driver should never use KERNEL_VERSION().

Re: [PATCH RESEND 0/7] Introduce MEDIA_VERSION to end KENREL_VERSION abuse in media

[Johannes Thumshirn]

On Sat, Jun 24, 2017 at 05:15:07PM -0300, Mauro Carvalho Chehab wrote:
> Sorry, but I can't see any advantage on it. On the downside, it
> includes the media controller header file (media.h) where it
> is not needed.

My reasoning was the differences in semantics. KERNEL_VERSION() is for
encoding the kernel's version triplet not a API or Hardware or whatever
version. Other subsystems do this as well, for instance in NVMe we have the
NVME_VS() macro which is used to encode the NVMe Spec compliance from a human
readable form to the hardware's u32. Also KERNEL_VERISON() shouldn't have
in-tree users IMHO. Yes there is _one_ other user of it in-tree which is EXT4
and I already talked to Jan Kara about it and we decided to leave it in until
4.20.

Byte,
Johannes
-- 
Johannes Thumshirn  Storage
jthumsh...@suse.de+49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH RESEND 0/7] Introduce MEDIA_VERSION to end KENREL_VERSION abuse in media

[Mauro Carvalho Chehab]

Em Wed, 21 Jun 2017 10:08:05 +0200
Johannes Thumshirn  escreveu:

> Currently the media subsystem has a very creative abuse of the
> KERNEL_VERSION macro to encode an arbitrary version triplet for media
> drivers and device hardware revisions.
> 
> This series introduces a new macro called MEDIA_REVISION which encodes
> a version triplet like KERNEL_VERSION does, but clearly has media
> centric semantics and doesn't fool someone into thinking specific
> parts are defined for a specific kernel version only like in out of
> tree drivers.

Sorry, but I can't see any advantage on it. On the downside, it
includes the media controller header file (media.h) where it
is not needed.

> 
> Johannes Thumshirn (7):
>   [media] media: introduce MEDIA_REVISION macro
>   video: fbdev: don't use KERNEL_VERSION macro for MEDIA_REVISION
>   [media] media: document the use of MEDIA_REVISION instead of
> KERNEL_VERSION
>   [media] cx25821: use MEDIA_REVISION instead of KERNEL_VERSION
>   [media] media: s3c-camif: Use MEDIA_REVISON instead of KERNEL_VERSION
>   [media] media: bcm2048: use MEDIA_REVISION isntead of KERNEL_VERSION
>   staging/atomisp: use MEDIA_VERSION instead of KERNEL_VERSION

That's said, some of the above shouldn't be using KERNEL_VERSION
at all. The V4L2 core sets the version already. So, drivers like
cx25821, s3c-camif, bcm2048 and atomisp are likely doing the wrong
thing.

Thanks,
Mauro

[PATCH RESEND 0/7] Introduce MEDIA_VERSION to end KENREL_VERSION abuse in media

[Johannes Thumshirn]

Currently the media subsystem has a very creative abuse of the
KERNEL_VERSION macro to encode an arbitrary version triplet for media
drivers and device hardware revisions.

This series introduces a new macro called MEDIA_REVISION which encodes
a version triplet like KERNEL_VERSION does, but clearly has media
centric semantics and doesn't fool someone into thinking specific
parts are defined for a specific kernel version only like in out of
tree drivers.

Johannes Thumshirn (7):
  [media] media: introduce MEDIA_REVISION macro
  video: fbdev: don't use KERNEL_VERSION macro for MEDIA_REVISION
  [media] media: document the use of MEDIA_REVISION instead of
KERNEL_VERSION
  [media] cx25821: use MEDIA_REVISION instead of KERNEL_VERSION
  [media] media: s3c-camif: Use MEDIA_REVISON instead of KERNEL_VERSION
  [media] media: bcm2048: use MEDIA_REVISION isntead of KERNEL_VERSION
  staging/atomisp: use MEDIA_VERSION instead of KERNEL_VERSION

 Documentation/media/uapi/cec/cec-ioc-adap-g-caps.rst| 2 +-
 Documentation/media/uapi/mediactl/media-ioc-device-info.rst | 4 ++--
 Documentation/media/uapi/v4l/vidioc-querycap.rst| 6 +++---
 drivers/media/pci/cx25821/cx25821.h | 2 +-
 drivers/media/platform/s3c-camif/camif-core.c   | 2 +-
 drivers/staging/media/atomisp/include/linux/atomisp.h   | 6 +++---
 drivers/staging/media/bcm2048/radio-bcm2048.c   | 2 +-
 drivers/video/fbdev/matrox/matroxfb_base.c  | 3 ++-
 include/media/media-device.h| 5 ++---
 include/uapi/linux/media.h  | 4 +++-
 10 files changed, 19 insertions(+), 17 deletions(-)

-- 
2.12.3