On Tue, Mar 04, 2025, Thinh Nguyen wrote: > On Wed, Feb 26, 2025, Bjorn Andersson wrote: > > In order to more tightly integrate the Qualcomm glue driver with the > > dwc3 core the driver is redesigned to avoid splitting the implementation > > using the driver model. But due to the strong coupling to the Devicetree > > binding needs to be updated as well. > > > > Various ways to provide backwards compatibility with existing Devicetree > > blobs has been explored, but migrating the Devicetree information > > between the old and the new binding is non-trivial. > > > > For the vast majority of boards out there, the kernel and Devicetree are > > generated and handled together, which in practice means that backwards > > compatibility needs to be managed across about 1 kernel release. > > > > For some though, such as the various Snapdragon laptops, the Devicetree > > blobs live a life separate of the kernel. In each one of these, with the > > continued extension of new features, it's recommended that users would > > upgrade their Devicetree somewhat frequently. > > > > With this in mind, simply carrying a snapshot/copy of the current driver > > is simpler than creating and maintaining the migration code. > > > > The driver is kept under the same Kconfig option, to ensure that Linux > > distributions doesn't drop USB support on these platforms. > > > > The driver, which is going to be refactored to handle the newly > > introduced qcom,snps-dwc3 compatible, is updated to temporarily not > > match against any compatible. > > > > This driver should be removed after 2 LTS releases. > > > > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxxxx> > > --- > > drivers/usb/dwc3/Makefile | 1 + > > drivers/usb/dwc3/dwc3-qcom-legacy.c | 934 ++++++++++++++++++++++++++++++++++++ > > drivers/usb/dwc3/dwc3-qcom.c | 1 - > > 3 files changed, 935 insertions(+), 1 deletion(-) > > > > This is a bit concerning if there's no matching compatible string. ie. > we don't have user for the new driver without downstream dependencies > (or some workaround in the driver binding). Ignore the comment above, I missed the "temporarily" in your log above. However, the comment below still stands. > > While I understand the intention, I'm afraid we may have to support and > maintain this much longer than the proposed 2 LTS releases (as seen with > anything tagged with "legacy" in the upstream kernel). If possible, I'd > prefer the complications of maintenance of the migration code be handled > downstream. > Thanks, Thinh
