Re: [PATCH v2 1/2] media: dt-bindings: Add dt bindings for m2m-deinterlace device

[Matthew Majewski <mattwmajewski@gmail.com>]

On Mon, 2025-03-03 at 08:31 +0100, Krzysztof Kozlowski wrote:
> On 26/02/2025 23:41, Matthew Majewski wrote:
> > 
> > As I wrote, supported devices/hardware is anything that provides a
> > MEM_TO_MEM capable dma-controller with interleaved transfer
> > support. I
> > did not list specific devices because the bindings are supposed to
> > be
> > generic, as they are not describing actual silicon. But if you want
> > me
> 
> I already told you that no. Bindings are not supposed to be generic.
> 
> From where did you get such information?

There are generic bindings in the kernel and I based my bindings off of
them. spi-gpio.yaml, i2c-gpio.yaml, video-mux.yaml, etc are all generic
bindings, no?

> 
> > to list some devices which provide a compatible dma-controller,
> > here
> > are devices I found in the current mainline kernel:
> > 
> > - TI OMAP Soc Family
> > - TI Davinci Soc Family
> > - TI Keystone Processor Family
> > - IMX27 Processor and variants
> > - Several Microchip Processors (sama5, sam9x7, sam9x60)
> 
> That's too generic - you just listed SoCs, which consist of dozen or
> hundred of devices. Which hardware piece is here?
> 
> Maybe this is not for a real device, but then this should be marked
> clearly.
> 

I listed devices that have a compatible dma-controller, so the list is
a bit big, sorry. I also specifically mentioned the BeagleBone black
board which I have been testing on. 

"m2m-deinterlace" used to be a part of the mach-imx27_visstrim_m10.c
board file, but was removed with commit 879c0e5e0ac711 (ARM: imx:
Remove i.MX27 board files). So at least the Vistrim M10 device was
explicitly using the m2m-deinterlace device. 

When the move away from board files was made towards device-tree, m2m-
deinterlace support was never ported over to device-tree. This is what
I am doing now. 

And yes, m2m-deinterlace is not a "real device" if by "real device" you
mean an actual piece of silicon on a specific piece of hardware. I
think there is just some semantic confusion here. I will no longer
refer to it as a "device" then, please let me know what the more
appropriate term is and I will modify the description accordingly.

> > 
> > I think an appropriate analogy for m2m-deinterlace would be spi-
> > gpio.
> > Since spi-gpio leverages gpio for bitbanging the spi protocol, the
> > bindings do not need to describe any clocks, spi-controller
> > registers,
> 
> Sure, SPI GPIO is Linux driver, not a device and I am asking about it
> all the time.
> 

My point was that spi-gpio has dt-bindings even though these bindings
do not describe a specific hardware device, hence it is "generic". 

Best,
Matthew