On Tue, Sep 14, 2021 at 02:11:18PM +0300, Laurent Pinchart wrote: > Hi Paul, > > On Tue, Sep 14, 2021 at 09:50:41AM +0200, Paul Kocialkowski wrote: > > On Mon 13 Sep 21, 10:31, Maxime Ripard wrote: > > > On Fri, Sep 10, 2021 at 08:41:45PM +0200, Paul Kocialkowski wrote: > > > > Some Allwinner platforms come with an Image Signal Processor, which > > > > supports various features in order to enhance and transform data > > > > received by image sensors into good-looking pictures. In most cases, > > > > the data is raw bayer, which gets internally converted to RGB and > > > > finally YUV, which is what the hardware produces. > > > > > > > > This driver supports ISPs that are similar to the A31 ISP, which was > > > > the first standalone ISP found in Allwinner platforms. Simpler ISP > > > > blocks were found in the A10 and A20, where they are tied to a CSI > > > > controller. Newer generations of Allwinner SoCs (starting with the > > > > H6, H616, etc) come with a new camera subsystem and revised ISP. > > > > Even though these previous and next-generation ISPs are somewhat > > > > similar to the A31 ISP, they have enough significant differences to > > > > be out of the scope of this driver. > > > > > > > > While the ISP supports many features, including 3A and many > > > > enhancement blocks, this implementation is limited to the following: > > > > - V3s (V3/S3) platform support; > > > > - Bayer media bus formats as input; > > > > - Semi-planar YUV (NV12/NV21) as output; > > > > - Debayering with per-component gain and offset configuration; > > > > - 2D noise filtering with configurable coefficients. > > > > > > > > Since many features are missing from the associated uAPI, the driver > > > > is aimed to integrate staging until all features are properly > > > > described. > > > > > > We can add new features/interfaces to a !staging driver. Why do you > > > think staging is required? > > > > This is true for the driver but not so much for the uAPI, so it seems that > > the uAPI must be added to staging in some way. Then I'm not sure it makes sense > > to have a !staging driver that depends on a staging uAPI. > > > > Besides that, I added it to staging because that's the process that was > > followed by rkisp1, which is a very similar case. > > Maxime is right in the sense that uAPI can always be extended, but it > has to be done in a backward-compatible manner, and staging is sometimes > considered as not being covered by the ABI stability requirements of the > kernel. Not everybody agrees on this, but there are clear cases where > userspace really can't expect staging ABIs to be stable (for instance > when the driver doesn't even compile). > > I think there's value in having the driver in staging to facilitate > development until we consider the ABI stable, but I'm not entirely sure > if there should be another step taken to mark this ABI is not being > ready yet. The rule seems to be about whether or not the user-space gets broken in the process: https://lore.kernel.org/lkml/CAHk-=wiVi7mSrsMP=fLXQrXK_UimybW=ziLOwSzFTtoXUacWVQ@xxxxxxxxxxxxxx/ Something that wouldn't compile cannot generate a regression, since it never worked in the first place. Changing the semantic of an ioctl does. Maxime
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