| Message ID | 20230321-topic-sagami_dp-v1-1-340c8bce4276@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | Enable DisplayPort over USB-C on SONY Sagami | expand |
On Tue, Mar 21, 2023 at 11:12:28PM +0100, Konrad Dybcio wrote: > The OnSemi NB7VPQ904M Type-C DP altmode redriver provides SBU signals > that can be used in with the gpio-sbu-mux driver. Document it. > > Note that the -mux suffix is there to indicate that the gpio-sbu-mux > driver interacts with the mux part of this otherwise quite sophisticated > chip, leaving the "onnn,nb7vpq904m" compatible free for when a proper > driver taking care of all of the chip's capabilities is introduced. You should define a proper and complete binding. If you want to bind the gpio-sbu-mux driver to it now until you have a proper driver then that's fine. When you have such a driver, then you drop the compatible from the gpio-sbu-mux driver. Note that having the fallback "gpio-sbu-mux" is somewhat problematic because the kernel has no mechanism to ensure you bind the most specific driver. For that to happen, it would have to support (automatically) unbinding one driver and binding to the more specific driver since one driver could be built-in and the other a module. Rob
On 30.03.2023 17:31, Rob Herring wrote: > On Tue, Mar 21, 2023 at 11:12:28PM +0100, Konrad Dybcio wrote: >> The OnSemi NB7VPQ904M Type-C DP altmode redriver provides SBU signals >> that can be used in with the gpio-sbu-mux driver. Document it. >> >> Note that the -mux suffix is there to indicate that the gpio-sbu-mux >> driver interacts with the mux part of this otherwise quite sophisticated >> chip, leaving the "onnn,nb7vpq904m" compatible free for when a proper >> driver taking care of all of the chip's capabilities is introduced. > > You should define a proper and complete binding. If you want to bind the > gpio-sbu-mux driver to it now until you have a proper driver then that's > fine. When you have such a driver, then you drop the compatible from the > gpio-sbu-mux driver. Okay, that makes perfect sense and is good to know. Perhaps even worth documenting somewhere. I think I'll delay resending this and get an "actual" driver going. Konrad > > Note that having the fallback "gpio-sbu-mux" is somewhat problematic > because the kernel has no mechanism to ensure you bind the most specific > driver. For that to happen, it would have to support (automatically) > unbinding one driver and binding to the more specific driver since one > driver could be built-in and the other a module. > > Rob
diff --git a/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml b/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml index bf4b1d016e1f..a7206009b691 100644 --- a/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml +++ b/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml @@ -20,6 +20,7 @@ properties: items: - enum: - onnn,fsusb43l10x + - onnn,nb7vpq904m-mux - pericom,pi3usb102 - const: gpio-sbu-mux
The OnSemi NB7VPQ904M Type-C DP altmode redriver provides SBU signals that can be used in with the gpio-sbu-mux driver. Document it. Note that the -mux suffix is there to indicate that the gpio-sbu-mux driver interacts with the mux part of this otherwise quite sophisticated chip, leaving the "onnn,nb7vpq904m" compatible free for when a proper driver taking care of all of the chip's capabilities is introduced. Ref: https://www.onsemi.com/products/signal-conditioning-control/redrivers/nb7vpq904m Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org> --- Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml | 1 + 1 file changed, 1 insertion(+)