On 11/4/20 8:17 AM, Paul Kocialkowski wrote: > Hi, > > On Mon 02 Nov 20, 10:21, Maxime Ripard wrote: >> On Fri, Oct 30, 2020 at 07:45:18PM -0300, Helen Koike wrote: >>> On 10/23/20 2:45 PM, Paul Kocialkowski wrote: >>>> The A31 MIPI CSI-2 controller is a dedicated MIPI CSI-2 controller >>>> found on Allwinner SoCs such as the A31 and V3/V3s. >>>> >>>> It is a standalone block, connected to the CSI controller on one side >>>> and to the MIPI D-PHY block on the other. It has a dedicated address >>>> space, interrupt line and clock. >>>> >>>> Currently, the MIPI CSI-2 controller is hard-tied to a specific CSI >>>> controller (CSI0) but newer SoCs (such as the V5) may allow switching >>>> MIPI CSI-2 controllers between CSI controllers. >>>> >>>> It is represented as a V4L2 subdev to the CSI controller and takes a >>>> MIPI CSI-2 sensor as its own subdev, all using the fwnode graph and >>>> media controller API. >>> >>> Maybe this is a bad idea, but I was thinking: >>> This driver basically just turn on/off and catch some interrupts for errors, >>> and all the rest of v4l2 config you just forward to the next subdevice >>> on the pipeline. >>> >>> So instead of exposing it as a subdevice, I was wondering if modeling >>> this driver also through the phy subsystem wouldn't be cleaner, so >>> you won't need all the v4l2 subdevice/topology boilerplate code that >>> it seems you are not using (unless you have plans to add controls or >>> some specific configuration on this node later). >>> >>> But this would require changes on the sun6i-csi driver. >>> >>> What do you think? >> >> Eventually we'll need to filter the virtual channels / datatypes I >> guess, so it's definitely valuable to have it in v4l2 Which kind of datatypes? I ask to know if this shouldn't be configured through the video node instead of subdevice. Regarding channels, we had a discussion to implement it through the video node (and not subdevice) [1]. But we discussed about blitters and multi-scalers, so now I'm wondering if we could use the same API for mipi-csi virtual channels in the video entity device, or if it doesn't apply and we need another API for that in a subdevice instead. [1] https://patchwork.linuxtv.org/project/linux-media/cover/20200717115435.2632623-1-helen.koike@xxxxxxxxxxxxx/ > > Agreed and like I mentionned in the discussion on 00/14 I don't think it > would be a cleaner way to expose things. > > There's also the fact that newer SoCs like the V5 seem to allow connecting > any MIPI CSI-2 controller to any CSI controller, so the graph representation > is definitely welcome here. I'm not sure this is an advantage in userspace pov, because it means we'll have different topologies for basically the same end result to userspace. But as I mentioned, I don't mind keeping it in the media topology. Helen > > Paul >
