[libcamera-devel] [RFC PATCH 2/2] libcamera: camera_sensor: Do not clear camera flips when listing formats
Jacopo Mondi
jacopo at jmondi.org
Fri Nov 4 11:39:08 CET 2022
Hi David
On Fri, Nov 04, 2022 at 09:58:41AM +0000, David Plowman wrote:
> Hi Jacopo, Dave, everyone
>
> Lots of discussion! And you all know far more about camera drivers
> than I ever want to, so I probably don't have that much to add.
>
> It seems to me like the choice of looking at that imx258 driver was a
> bit unlucky. As far as I could see, it simply has no HFLIP or VFLIP
> controls at all, and so doesn't really affect the debate here (I
> think, am I right?). I notice that on our linux tree it is supported -
> which I take to be all of Dave's magic!
>
Yeah, sorry for the long emails, in the end it was mostly me being confused
and Dave clarifying things
I'm about to test these patches on RkISP1 and then I'll finally review
them without any further digression
> On Thu, 3 Nov 2022 at 17:29, Jacopo Mondi <jacopo at jmondi.org> wrote:
> >
> > Hi Dave
> >
> > On Thu, Nov 03, 2022 at 04:26:07PM +0000, Dave Stevenson wrote:
> > > Hi Jacopo
> > >
> > > On Thu, 3 Nov 2022 at 15:26, Jacopo Mondi <jacopo at jmondi.org> wrote:
> > > >
> > > > Hi again
> > > >
> > > > On Thu, Nov 03, 2022 at 11:52:23AM +0000, Dave Stevenson via libcamera-devel wrote:
> > > > > On Thu, 3 Nov 2022 at 11:24, David Plowman
> > > > > <david.plowman at raspberrypi.com> wrote:
> > > > > >
> > > > > > Hi Dave
> > > > > >
> > > > > > On Thu, 3 Nov 2022 at 11:02, Dave Stevenson
> > > > > > <dave.stevenson at raspberrypi.com> wrote:
> > > > > > >
> > > > > > > Hi David
> > > > > > >
> > > > > > > On Thu, 3 Nov 2022 at 10:40, David Plowman via libcamera-devel
> > > > > > > <libcamera-devel at lists.libcamera.org> wrote:
> > > > > > > >
> > > > > > > > Previously the code used to clear the camnera's h and v flip bits when
> > > > > > > > enumerating the supported formats so as to obtain any Bayer formats in
> > > > > > > > the sensor's native (untransformed) orientation. However this fails
> > > > > > > > when the camera is already in use elsewhere.
> > > > > > > >
> > > > > > > > Instead, we query the current state of the flip bits and transform the
> > > > > > > > formats - which we obtain in their flipped orientation - back into
> > > > > > > > their native orientation to be stored.
> > > > > > >
> > > > > > > I don't believe that libcamera knows for definite whether the sensor
> > > > > > > changes the Bayer order or not. Several of the OnSemi sensors I have
> > > > > > > seen do not change, presumably as they shift their crop by 1 pixel.
> > > > > >
> > > > > > Yes, that's a good point. I've vaguely assumed that I can check the
> > > > > > control's V4L2_CTRL_FLAG_MODIFY_LAYOUT to discover whether this is the
> > > > > > case or not, but as we keep on discovering, there may be no guarantees
> > > > > > about this. Do we know what these particular sensors do here? The Pi
> > > > > > PH actually already assumes this flag "works", so the changes here
> > > > > > possibly don't make anything worse, though they do engrain the
> > > > > > assumption more deeply...
> > > > >
> > > > > Yes I believe V4L2_CTRL_FLAG_MODIFY_LAYOUT should do what you want.
> > > > >
> > > > > The OnSemi sensors I'm thinking of don't have drivers in mainline, so
> > > > > there's no driver to check currently.
> > > > >
> > > > > Looking at mainline, only imx219 and imx258 set the flag.
> > > > > - ov2680, imx208, imx319, imx355, mt9m001, ov08d10 all change the
> > > > > order but don't set V4L2_CTRL_FLAG_MODIFY_LAYOUT
> > > > > - hi847 and ov13b10 move the crop to maintain the Bayer order.
> > > > > - imx274 and ov5648 only ever report one order, but supports flips and
> > > > > has no apparent cropping shift.
> > > > > - I have missed it in my imx290 patches to add flips that I was about to send!
> > > > >
> > > > > So, as Jacopo summarised the situation on event handlers for controls,
> > > > > room for improvement!
> > > > >
> > > >
> > > > To add more pleasure, as discussed on a review comment on Dave's
> > > > series
> > > > https://patchwork.linuxtv.org/project/linux-media/patch/20221005152809.3785786-12-dave.stevenson@raspberrypi.com/
> > > > Some sensors assumes to be rotated and bury their rotation
> > > > settings in their register tables.
> > > >
> > > > In the example of the imx258 sensor Dave has mentioned:
> > > >
> > > > - The bayer order reported through the format is GRBG
> > > > https://github.com/torvalds/linux/blob/master/drivers/media/i2c/imx258.c#L822
> > > >
> > > > - The sensor driver applies mirroring by default at s_stream
> > > > time (without specifying the direction, vertical or horizontal)
> > > >
> > > > /* Set Orientation be 180 degree */
> > > > ret = imx258_write_reg(imx258, REG_MIRROR_FLIP_CONTROL,
> > > > IMX258_REG_VALUE_08BIT, REG_CONFIG_MIRROR_FLIP);
> > >
> > > #define REG_CONFIG_MIRROR_FLIP 0x03 [1]
> > > so this is doing BOTH H & V flips in one hit.
> > >
> > > Datasheet for imx258 at [2].
> >
> > Your google-fu is certainly better than mine
> >
> > >
> > > [1] https://github.com/torvalds/linux/blob/master/drivers/media/i2c/imx258.c#L78
> > > [2] https://web.archive.org/web/20201027131326/www.hi.app/IMX258-datasheet.pdf
> > >
> > > > - I found an interesting comment on the patch series changelog:
> > > > https://www.spinics.net/lists/linux-media/msg133840.html
> > > > Output order of test pattern is always BGGR, so it needs a flip to
> > > > rotate bayer pattern to required one (GRBG)
> > >
> > > It's not uncommon that the test patterns are independent of flips as
> > > there is no image array to read out in the reverse direction.
> > > There are often 4 registers to configure the values to stick into each
> > > of the 4 colour channels, and those are simply inserted in order.
> > > Registers 0x0602-0x0609 on IMX258.
> >
> > Thanks, indeed my assumption that the test pattern was reflecting the
> > native order was incorrect
> >
> > >
> > > TBH I've never understood the love of implementing test patterns in
> > > drivers. If a driver is merged into mainline then there should be a
> > > fair confidence that it works, therefore why worry about test
> > > patterns? Isn't a captured image more valuable?
> > >
> > > > So it might seem legit to presume the native Bayer pattern on the
> > > > pixel array is BGGR, read from the right-bottom corner:
> > >
> > > I'm not sure if you're referencing imx258 specifically here, or
> > > talking generically.
> > > imx258 is a total mess, and I need to get around to upstreaming my
> > > patches at [3].
> > >
> > > The native Bayer order for imx258 is RGGB (see Fig 5-4 page 84, Fig
> > > 5-3 page 79, and several places in section 4). Surely the datasheet
> > > has to count as definitive.
> > >
> >
> > Indeed
> >
> > > As in patch [4], Y_ADD_STA register is set to 0, and Y_ADD_END to
> > > 3118, giving 3119 lines total for 3118 lines of readout. The hardcoded
> > > V flip on that starts us on the "wrong" line of the Bayer pattern for
> > > any sane person looking at it and trying to work out what the heck is
> > > going on - we're still getting RGGB. H flip that and the resulting
> > > Bayer order is GRBG. QED.
> > >
> >
> > As usual, everything works by chance!
> >
> > With a correct Y_ADD_END we would then get
> >
> > RGGB -> vflip -> GBRG -> hflip -> BGGR
> >
> > It mean that fixing the driver will imply changing the reported
> > bayer pattern I presume..
> >
> > > [3] https://github.com/raspberrypi/linux/commits/rpi-5.15.y/drivers/media/i2c/imx258.c
> > > [4] https://github.com/raspberrypi/linux/commit/1942d0da85bac79f3d2a1c2d8e797e97bd16b618
> >
> > Ah yes it does :)
> >
> > >
> > > >
> > > > RG RG RG RG RG
> > > > GB GB GB GB GB
> > > > (1, n) RG RG RG RG RG (1,0)
> > > > GB GB GB GB GB
> > > > (0, n) <-- (0,0)
> > > >
> > > > To obtain the Bayer GRBG order advertised as output format I presume the
> > > > REG_CONFIG_MIRROR_FLIP vertically flips the image, moving the (0,0)
> > > > pixel coordinate, from where reading is started, on the top-right corner:
> > > >
> > > > (0, n) <-- (0,0)
> > > > RG RG RG RG RG
> > > > (1, n) GB GB GB GB GB (1, 0)
> > > > RG RG RG RG RG
> > > > GB GB GB GB GB
> > >
> > > Due to the error on Y_ADD_END, implementing a VFLIP gave no change in
> > > Bayer order! Work that one out in userspace (although it is a driver
> > > bug that causes it).
> > >
> > > > According to your below patch and Bayer::transform():
> > > > - BGGR becomes GRBG via a vertical flip, right ? So this should
> > > > confirm the above assumption about an unconditional vertical flip
> > > >
> > > > If the driver would register flip controls, it would register them as
> > > > VFLIP = 1, HFLIP = 0. Here below you would get GRBG, vertically
> > > > transform it to BGGR and store BGGR as "native" format, but now you
> > > > won't be able to apply it to the sensor, as it only supports GRBG.
> > > >
> > > > What drivers should do is to register somehow their -native- Bayer
> > > > pattern, use a generic BAYER format in set_fmt and let userspace deal
> > > > with rotations and Bayer pattern re-odering as userspace is
> > > > able to access the mounting rotation via the CID_CAMERA_ROTATION
> > > > control.
> > >
> > > Doing so goes against the V4L2 principle of the V4L2_PIX_FMT_* telling
> > > you exactly how to interpret the pixel data.
> > >
> > > I need to check the wording, but I thought CID_CAMERA_ROTATION told
> > > you the orientation of the sensor within the device such that you
> > > could stick it into EXIF or similar metadata. It doesn't tell you how
> > > the Bayer order would change.
> > >
> >
> > Rotation != flipping, you're right I was mixing the two.
> >
> > > > Unfortunately no driver afaict behaves this way. They might report via
> > > > v4l2-ctl if any flip is applied to them, as Dave does in the series,
> > > > but adjusting the Bayer pattern as you do below might lead to results
> > > > that won't apply on the sensor. Do you agree or did I get lost ?
> > >
> > > AIUI At the point of actually wanting to stream, flips will be
> > > applied, and the format reported by the sensor driver will then be
> > > used to configure the rest of the pipeline.
> > > I hope that userspace never thinks it knows better than the driver
> > > with regard to Bayer order - as above there are enough quirks that it
> > > will get it wrong.
> > >
> >
> > just for sake of discussion:
> > libcamera would simply get from somewhere (driver or sensor properties
> > database) the native (or non-rotated) format, inspect the flips and
> > know what format report to applications. Driver will accept a wildcard
> > BAYER format. But yes, good luck configuring the pipeline if any
> > component along the way is sensible to the bayer ordering.
> >
> > > > To be honest I would drop clearing the flips, and to
> > > > protect against concurrent usages, validate that the current flip values
> > > > match the default controls value. If the two do not match, and the
> > > > driver advertises V4L2_CTRL_FLAG_MODIFY_LAYOUT, it means the mbus code
> > > > we're seeing right now is the result of another user having flipped
> > > > the image. In this case you could flip the format like you're doing
> > > > below to obtain the "unflipped" Bayer pattern, as we know it will work
> > > > as it is the "defaul configuration" order.
> > >
> > > A colour equivalent to ov9282 is going to blow up your assumption on
> > > default value. The original driver didn't support flips, but H & V
> > > flipped the image (much like imx258), so to avoid regressions we have
> > > a default of being flipped.
> >
> > Not sure I get why. The color equivalent will report the bayer order
> > of the H&V flipped Bayer format version. According to
> > your series, it will also report VFLIP = HFLIP = 1 by default and
> > read-only. As they're RO, no V4L2_CTRL_FLAG_MODIFY_LAYOUT flag is
> > registered, and no transform is applied. The sensor will only speak
> > the rot180 bayer format version.
> >
> > The patch below transforms only if V4L2_CTRL_FLAG_MODIFY_LAYOUT, which
> > implies the driver can speak the non-modified format too, so I guess
> > it works under the assumptions that:
> >
> > 1) Drivers report all the flips they apply implicitly and not all of
> > them do
> > 2) They correctly register V4L2_CTRL_FLAG_MODIFY_LAYOUT if flip
> > modifies the bayer pattern order and as you noticed not all of them
> > do so
>
> There are definitely some corner cases to check here. I think we're
> fine if there are simply no H/VFLIP controls, but what if they exist
> and are read-only? What if they're writable but allow only a single
> value? And what to do about drivers that aren't behaving as we expect.
What to do if they're RO or only have a single value:
I expect that they do not register any V4L2_CTRL_FLAG_MODIFY_LAYOUT
flag, they should support a single bayer order which is the one
reported in the format, and your patch won't transform it because the
above mentioned flag isn't there. Do you agree with this ?
What to do if the driver is broken: I would say it has to be fixed,
but we should at least try not to fail too hard. Ofc it depends on how
broken the driver is, but I guess it's legit to assume the driver is
somewhat compliant...
>
> I think things will always work out and after configure() you should
> see the correct Bayer pattern, but good luck to applications trying to
> figure out what raw format to ask for.
>
> I know I've commented, as have others, that specifying the actual
> Bayer order in the application is not really useful, though things
> like bit depth and packing are. Any strong expectation to get the
> Bayer order right would be quite onerous - it would be much more
> helpful to be able to ask for that XXXX ("whatever!") Bayer order!
I agree in principle, but I don't see it happening anytime soon in
V4L2 :)
>
> David
>
> >
> > I guess it will be hard to compliance-check drivers for that and this
> > requirements will have to be enforced during review, possibly by
> > inspecting the register tables making sure any flip bit is there
> > silently set.
> >
> > > Same would have been true for imx258, except that there the original
> > > driver read the "rotation" fwnode parameter and ensured it was 180. I
> > > think that is now going to be incorrectly interpreted as the sensor
> > > has done the rot180, and it will tell userspace rot180 as well, so
> > > EXIF headers etc will say that it is stored inverted.
> > >
> >
> > Yes, the ROTATION property should not be used to decide if the driver
> > should flip or not, but just by application to correctly visualize the
> > images..
> >
> > > > Final question, and sorry for the long email, but what would it be the
> > > > real purpose of obtaining the native bayer pattern order in your use case. I
> > > > presume we had that attempt to get the native format because android
> > > > wants to have the native order reported. I think that CameraSensor
> > > > should instead try to use a bayer order that work for the drive in its
> > > > default configuration which, if the driver claims to be rotated by
> > > > default, won't match the actual native order.
> > > >
> > > > We have a camera properties database where such native information
> > > > could eventually be stored if it's of interest!
> > >
> > > Store it in two places - increase the chance of it being wrong! ;)
> > >
> > > I am starting to write a guide for things to check with sensor
> > > drivers, so hopefully future drivers will do what is defined as the
> > > correct thing. Perhaps we'll find the time to fix older drivers - I'm
> > > just doing a patch set for V4L2_CTRL_FLAG_MODIFY_LAYOUT.
> > >
> >
> > Thanks, hopefully this will increases the sensor drivers consistency in
> > the kernel.
> >
> > > Dave
> > >
> > > > Hope I didn't get lost!
> > > >
> > > > > Dave
> > > > >
> > > > > > Presumably you can rely on the formats being returned correctly after
> > > > > > setting the flip bits, though having to re-query the formats from the
> > > > > > device like that would be irritating too. And you'd never be able to
> > > > > > predict the format ahead of time, only after setting it. I don't know
> > > > > > if that's better or worse than saying "change the driver". Opinions
> > > > > > welcome on that one!
> > > > > >
> > > > > > To be honest I always have difficulty with the Bayer order being part
> > > > > > of the format. An application might legitimately want to have a say
> > > > > > about the bit depth or packing, but the Bayer order?? Being able to
> > > > > > request an XXXX ("anything goes") Bayer order, which gets updated once
> > > > > > the sensor is configured, would be much more application-friendly. But
> > > > > > another can of worms!!
> > > >
> > > > Agreed, userspace has all the information to adjust the ordering as it
> > > > likes..
> > > >
> > > > > >
> > > > > > David
> > > > > >
> > > > > > >
> > > > > > > The original comment mentioned that scenario:
> > > > > > > "This is harmless for sensors where the flips don't affect the Bayer order"
> > > > > > >
> > > > > > > Dave
> > > > > > >
> > > > > > > > Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> > > > > > > > ---
> > > > > > > > src/libcamera/camera_sensor.cpp | 51 +++++++++++++++++++++++++++------
> > > > > > > > 1 file changed, 43 insertions(+), 8 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp
> > > > > > > > index 572a313a..6670dfb9 100644
> > > > > > > > --- a/src/libcamera/camera_sensor.cpp
> > > > > > > > +++ b/src/libcamera/camera_sensor.cpp
> > > > > > > > @@ -19,6 +19,8 @@
> > > > > > > >
> > > > > > > > #include <libcamera/base/utils.h>
> > > > > > > >
> > > > > > > > +#include <libcamera/transform.h>
> > > > > > > > +
> > > > > > > > #include "libcamera/internal/bayer_format.h"
> > > > > > > > #include "libcamera/internal/camera_lens.h"
> > > > > > > > #include "libcamera/internal/camera_sensor_properties.h"
> > > > > > > > @@ -108,18 +110,51 @@ int CameraSensor::init()
> > > > > > > > return ret;
> > > > > > > >
> > > > > > > > /*
> > > > > > > > - * Clear any flips to be sure we get the "native" Bayer order. This is
> > > > > > > > - * harmless for sensors where the flips don't affect the Bayer order.
> > > > > > > > + * We want to get the native mbus codes for the sensor, without any flips.
> > > > > > > > + * We can't clear any flips here, so we have to read the current values
> > > > > > > > + * (if the flip controls exist), decide whether they actually modify any
> > > > > > > > + * output Bayer pattern, and finally undo their effect on the formats.
> > > > > > > > + *
> > > > > > > > + * First, check if the flip controls exist and if so read them.
> > > > > > > > */
> > > > > > > > ControlList ctrls(subdev_->controls());
> > > > > > > > - if (subdev_->controls().find(V4L2_CID_HFLIP) != subdev_->controls().end())
> > > > > > > > - ctrls.set(V4L2_CID_HFLIP, 0);
> > > > > > > > - if (subdev_->controls().find(V4L2_CID_VFLIP) != subdev_->controls().end())
> > > > > > > > - ctrls.set(V4L2_CID_VFLIP, 0);
> > > > > > > > - subdev_->setControls(&ctrls);
> > > > > > > > + std::vector<uint32_t> flipCtrlIds;
> > > > > > > > + bool hasHflip = subdev_->controls().find(V4L2_CID_HFLIP) != subdev_->controls().end();
> > > > > > > > + bool hasVflip = subdev_->controls().find(V4L2_CID_VFLIP) != subdev_->controls().end();
> > > > > > > > + if (hasHflip)
> > > > > > > > + flipCtrlIds.push_back(V4L2_CID_HFLIP);
> > > > > > > > + if (hasVflip)
> > > > > > > > + flipCtrlIds.push_back(V4L2_CID_VFLIP);
> > > > > > > > + ControlList flipCtrls = subdev_->getControls(flipCtrlIds);
> > > > > > > > +
> > > > > > > > + /* Now construct a transform that would undo any flips. */
> > > > > > > > + Transform transform = Transform::Identity;
> > > > > > > > + if (hasHflip && flipCtrls.get(V4L2_CID_HFLIP).get<int>()) {
> > > > > > > > + const struct v4l2_query_ext_ctrl *extCtrl = subdev_->controlInfo(V4L2_CID_HFLIP);
> > > > > > > > + if (extCtrl->flags & V4L2_CTRL_FLAG_MODIFY_LAYOUT)
> > > > > > > > + transform |= Transform::HFlip;
> > > > > > > > + }
> > > > > > > > + if (hasVflip && flipCtrls.get(V4L2_CID_VFLIP).get<int>()) {
> > > > > > > > + const struct v4l2_query_ext_ctrl *extCtrl = subdev_->controlInfo(V4L2_CID_VFLIP);
> > > > > > > > + if (extCtrl->flags & V4L2_CTRL_FLAG_MODIFY_LAYOUT)
> > > > > > > > + transform |= Transform::VFlip;
> > > > > > > > + }
> > > > > > > > +
> > > > > > > > + /* Finally get the formats, and apply the transform to the mbus codes. */
> > > > > > > > + auto formats = subdev_->formats(pad_);
> > > > > > > > + for (const auto &format : formats) {
> > > > > > > > + unsigned int mbusCode = format.first;
> > > > > > > > + BayerFormat bayerFormat = BayerFormat::fromMbusCode(mbusCode);
> > > > > > > > + bool valid = true;
> > > > > > > > +
> > > > > > > > + if (bayerFormat.isValid())
> > > > > > > > + mbusCode = bayerFormat.transform(transform).toMbusCode(valid);
> > > > > > > > +
> > > > > > > > + if (valid)
> > > > > > > > + formats_[mbusCode] = std::move(format.second);
> > > > > > > > + }
> > > > > > > >
> > > > > > > > /* Enumerate, sort and cache media bus codes and sizes. */
> > > > > > > > - formats_ = subdev_->formats(pad_);
> > > > > > > > if (formats_.empty()) {
> > > > > > > > LOG(CameraSensor, Error) << "No image format found";
> > > > > > > > return -EINVAL;
> > > > > > > > --
> > > > > > > > 2.30.2
> > > > > > > >
More information about the libcamera-devel
mailing list