Rockchip USB revisited

[Stefan Kalkowski]

Hi Michael,

On Tue, Mar 14, 2023 at 07:21:20PM +0100, Michael Grunditz wrote:
> > That directory is there , so I have no clue what it means.
> >
> > Michael
> 
> Just thinking ... the dde_linux driver is much better for me. Much
> more generic. Is it possible to drive that from my rockchip dir? I
> have tried that before without luck. If I put a driver in
> dde_linux/src/drivers/usb_host/spec/ and enable dde_linux in
> build.conf I get a working driver.

I understand that this might be frustrating, but the mentioned
usb_host driver and the underlying legacy lx_emul approach are
deprecated and will vanish soon.

Apart from the quite old Linux code base, it is not economically
senseful for us to maintain this approach any longer. Therefore, I
would strongly encourage you to better follow the first approach you
took.

> 
> To be honest , I think that having generic ohci, ehci and xhci and use
> linux kernel for phy is a better approach rather than doing the whole
> driver stack for each platform.
> 
> I would be happy to get some input on this.

I agree, it would be desireable to have generic protocols for the
different USB specifications, as well as HUB handling, device
detection, resetting etc.. However, from our team's perspective it is
too complex to stem this development (beside all other important
work to do) without significant funding or otherwise strong external
motivation.

Using the Linux kernel drivers is simply an economic decision. When
using the latest lx_emul/lx_kit approach it tooks very few days to
enable a new driver, and it tooks even less to update the code base,
which is not the case with the deprecated dde_linux usb_host driver
mentioned above. I hope you can understand this motivation.
However, if you are strongly motivated to implement dedicated USB
protocol stacks from scratch, I assume nobody will argue against it.

Regards
Stefan

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-- 
Stefan Kalkowski
Genode labs

https://github.com/skalk | https://genode.org