linux-kernel - Re: [PATCH] [media] imx: csi: retain current field order and colorimetry setting as default

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Date:   Thu, 6 Apr 2017 15:38:56 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     Philipp Zabel <p.zabel@...gutronix.de>,
        Steve Longerbeam <slongerbeam@...il.com>, robh+dt@...nel.org,
        mark.rutland@....com, shawnguo@...nel.org, kernel@...gutronix.de,
        fabio.estevam@....com, mchehab@...nel.org, nick@...anahar.org,
        markus.heiser@...marIT.de,
        laurent.pinchart+renesas@...asonboard.com, bparrot@...com,
        geert@...ux-m68k.org, arnd@...db.de, sudipm.mukherjee@...il.com,
        minghsiu.tsai@...iatek.com, tiffany.lin@...iatek.com,
        jean-christophe.trotin@...com, horms+renesas@...ge.net.au,
        niklas.soderlund+renesas@...natech.se, robert.jarzmik@...e.fr,
        songjun.wu@...rochip.com, andrew-ct.chen@...iatek.com,
        gregkh@...uxfoundation.org, shuah@...nel.org,
        sakari.ailus@...ux.intel.com, pavel@....cz,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH] [media] imx: csi: retain current field order and
 colorimetry setting as default

On Thu, Apr 06, 2017 at 04:20:21PM +0200, Hans Verkuil wrote:
> On 04/06/2017 03:55 PM, Philipp Zabel wrote:
> > If the the field order is set to ANY in set_fmt, choose the currently
> > set field order. If the colorspace is set to DEFAULT, choose the current
> > colorspace.  If any of xfer_func, ycbcr_enc or quantization are set to
> > DEFAULT, either choose the current setting, or the default setting for the
> > new colorspace, if non-DEFAULT colorspace was given.
> > 
> > This allows to let field order and colorimetry settings be propagated
> > from upstream by calling media-ctl on the upstream entity source pad,
> > and then call media-ctl on the sink pad to manually set the input frame
> > interval, without changing the already set field order and colorimetry
> > information.
> > 
> > Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
> > ---
> > This is based on imx-media-staging-md-v14, and it is supposed to allow
> > configuring the pipeline with media-ctl like this:
> > 
> > 1) media-ctl --set-v4l2 "'tc358743 1-000f':0[fmt:UYVY8_1X16/1920x1080]"
> > 2) media-ctl --set-v4l2 "'imx6-mipi-csi2':1[fmt:UYVY8_1X16/1920x108]"
> > 3) media-ctl --set-v4l2 "'ipu1_csi0_mux':2[fmt:UYVY8_1X16/1920x1080]"
> > 4) media-ctl --set-v4l2 "'ipu1_csi0':0[fmt:UYVY8_1X16/1920x1080@...0]"
> > 5) media-ctl --set-v4l2 "'ipu1_csi0':2[fmt:AYUV32/1920x1080@...0]"
> > 
> > Without having step 4) overwrite the colorspace and field order set on
> > 'ipu1_csi0':0 by the propagation in step 3).
> > ---
> >  drivers/staging/media/imx/imx-media-csi.c | 34 +++++++++++++++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> > 
> > diff --git a/drivers/staging/media/imx/imx-media-csi.c b/drivers/staging/media/imx/imx-media-csi.c
> > index 64dc454f6b371..d94ce1de2bf05 100644
> > --- a/drivers/staging/media/imx/imx-media-csi.c
> > +++ b/drivers/staging/media/imx/imx-media-csi.c
> > @@ -1325,6 +1325,40 @@ static int csi_set_fmt(struct v4l2_subdev *sd,
> >  	csi_try_fmt(priv, sensor, cfg, sdformat, crop, compose, &cc);
> >  
> >  	fmt = __csi_get_fmt(priv, cfg, sdformat->pad, sdformat->which);
> > +
> > +	/* Retain current field setting as default */
> > +	if (sdformat->format.field == V4L2_FIELD_ANY)
> > +		sdformat->format.field = fmt->field;
> 
> sdformat->format.field should never be FIELD_ANY. If it is, then that's a
> subdev bug and I'm pretty sure FIELD_NONE was intended.

Please explain further - sdformat->format.field is the field passed _in_
from userspace, and from what I can see, userspace is free to pass in
any value through the ioctl as check_format() does nothing to validate
that the various format.* fields are sane.

This patch is detecting that the user is requesting FIELD_ANY, and
fixing it up.  Surely that's the right thing to do, and is way more
preferable than just accepting the FIELD_ANY from userspace and
storing that value?

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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