Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1599815

Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and getting of frame rates

Show all headers | View raw

On Mon, Mar 13, 2017 at 10:56:46PM +0200, Sakari Ailus wrote:
> Hi Russell,
> 
> On Mon, Mar 13, 2017 at 01:27:02PM +0000, Russell King - ARM Linux wrote:
> > On Mon, Mar 13, 2017 at 03:16:48PM +0200, Sakari Ailus wrote:
> > > The vast majority of existing drivers do not implement them nor the user
> > > space expects having to set them. Making that mandatory would break existing
> > > user space.
> > > 
> > > In addition, that does not belong to link validation either: link validation
> > > should only include static properties of the link that are required for
> > > correct hardware operation. Frame rate is not such property: hardware that
> > > supports the MC interface generally does not recognise such concept (with
> > > the exception of some sensors). Additionally, it is dynamic: the frame rate
> > > can change during streaming, making its validation at streamon time useless.
> > 
> > So how do we configure the CSI, which can do frame skipping?
> > 
> > With what you're proposing, it means it's possible to configure the
> > camera sensor source pad to do 50fps.  Configure the CSI sink pad to
> > an arbitary value, such as 30fps, and configure the CSI source pad to
> > 15fps.
> > 
> > What you actually get out of the CSI is 25fps, which bears very little
> > with the actual values used on the CSI source pad.
> > 
> > You could say "CSI should ask the camera sensor" - well, that's fine
> > if it's immediately downstream, but otherwise we'd need to go walking
> > down the graph to find something that resembles its source - there may
> > be mux and CSI2 interface subdev blocks in that path.  Or we just accept
> > that frame rates are completely arbitary and bear no useful meaning what
> > so ever.
> 
> The user is responsible for configuring the pipeline. It is thus not
> unreasonable to as the user to configure the frame rate as well if there are
> device in the pipeline that can affect the frame rate. The way I proposed to
> implement it is compliant with the existing API and entirely deterministic,
> contrary to what you're saying.

You haven't really addressed my point at all.

What you seem to be saying is that you're quite happy for the situation
(which is a total misconfiguration) to exist.  Given the vapourware of
userspace (which I don't see changing in any kind of reasonable timeline)
I think this is completely absurd.

I'll state clearly now: everything that we've discussed so far, I'm
finding very hard to take anything you've said seriously.  I think we
have very different and incompatible point of views about what is
acceptable from a user point of view, so much so that we're never going
to agree on any point.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Sakari Ailus <sakari.ailus@iki.fi> - 2017-03-13 14:20 +0100
  Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-03-13 14:30 +0100
    Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Philipp Zabel <p.zabel@pengutronix.de> - 2017-03-13 15:00 +0100
      Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Steve Longerbeam <slongerbeam@gmail.com> - 2017-03-13 19:10 +0100
        Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Sakari Ailus <sakari.ailus@iki.fi> - 2017-03-13 22:10 +0100
          Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-03-13 22:40 +0100
          Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Hans Verkuil <hverkuil@xs4all.nl> - 2017-03-14 08:40 +0100
            Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Philipp Zabel <p.zabel@pengutronix.de> - 2017-03-14 11:50 +0100
    Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Sakari Ailus <sakari.ailus@iki.fi> - 2017-03-13 22:00 +0100
      Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and  getting of frame rates Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-03-13 22:10 +0100

csiph-web