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Th= e >> > > node is registered with the software SVC (gb-softsvc), which handles= the >> > > SVC protocol on behalf of the AP, so no dedicated coprocessor runnin= g >> > > SVC firmware is needed. >> > >=20 >> > > Greybus messages are carried over HDLC framing on the wire. Each fra= me >> > > carries a one-byte address (0x01 for Greybus) and control byte, foll= owed >> > > by the 16-bit CPort ID and the Greybus message itself. >> > >=20 >> > > Port parameters are taken from the firmware node: "baudrate" if >> > > present, otherwise 115200, with flow control and parity disabled. >> > >=20 >> > > Since gb-uart-node imports types from gb-softsvc, Rust to Rust calli= ng >> > > setup from nova-core [0] is being used. >> > >=20 >> > > [0]: https://lore.kernel.org/all/20260622-nova-exports-v5-0-6191773f= c977@nvidia.com/ >> > >=20 >> > > Signed-off-by: Ayush Singh >> > > --- >> > > MAINTAINERS | 1 + >> > > drivers/greybus/.gitignore | 1 + >> > > drivers/greybus/Kconfig | 15 +++ >> > > drivers/greybus/Makefile | 48 ++++++++ >> > > drivers/greybus/gb_uart_node.rs | 245 ++++++++++++++++++++++++++++= ++++++++++++ >> > > 5 files changed, 310 insertions(+) >> > >=20 >> > > diff --git a/MAINTAINERS b/MAINTAINERS >> > > index d047090be5f4..49c6dac72748 100644 >> > > --- a/MAINTAINERS >> > > +++ b/MAINTAINERS >> > > @@ -11339,6 +11339,7 @@ M: Ayush Singh >> > > L: greybus-dev@lists.linaro.org (moderated for non-subscribers) >> > > S: Maintained >> > > F: Documentation/devicetree/bindings/beagle/beagle,beagleconnect-f= reedom.yaml >> > > +F: drivers/greybus/gb_uart_node.rs >> > > =20 >> > > GREYBUS SUBSYSTEM >> > > M: Johan Hovold >> > > diff --git a/drivers/greybus/.gitignore b/drivers/greybus/.gitignore >> > > new file mode 100644 >> > > index 000000000000..ff9c4a3539b4 >> > > --- /dev/null >> > > +++ b/drivers/greybus/.gitignore >> > > @@ -0,0 +1 @@ >> > > +exports_gb_softsvc_generated.h >> > > diff --git a/drivers/greybus/Kconfig b/drivers/greybus/Kconfig >> > > index 381d1a6ee135..34de913af287 100644 >> > > --- a/drivers/greybus/Kconfig >> > > +++ b/drivers/greybus/Kconfig >> > > @@ -60,5 +60,20 @@ config GREYBUS_SOFTSVC >> > > To compile this code as a module, choose M here: the module >> > > will be called gb-softsvc.ko >> > > =20 >> > > +config GREYBUS_UART_NODE >> > > + tristate "Greybus UART node transport" >> > > + depends on RUST >> > > + depends on GREYBUS_SOFTSVC >> > > + depends on RUST_SERIAL_DEV_BUS_ABSTRACTIONS >> > > + select RUST_CRC_CCITT_ABSTRACTIONS >> > > + help >> > > + Select this option if you have a Greybus node connected over a >> > > + serial port. The node is registered with the software SVC, which >> > > + handles the SVC protocol on behalf of the AP, so no dedicated >> > > + coprocessor running SVC firmware is required. >> > > + >> > > + To compile this code as a module, choose M here: the module >> > > + will be called gb-uart-node.ko >> > > + >> > > endif # GREYBUS >> > > =20 >> > > diff --git a/drivers/greybus/Makefile b/drivers/greybus/Makefile >> > > index e6f594128802..81151963c01e 100644 >> > > --- a/drivers/greybus/Makefile >> > > +++ b/drivers/greybus/Makefile >> > > @@ -28,3 +28,51 @@ obj-$(CONFIG_GREYBUS_ES2) +=3D gb-es2.o >> > > obj-$(CONFIG_GREYBUS_SOFTSVC) +=3D gb-softsvc.o >> > > gb-softsvc-y +=3D gb_softsvc.o gb_softsvc_exports.o >> > > =20 >> > > +obj-$(CONFIG_GREYBUS_UART_NODE) +=3D gb-uart-node.o >> > > +gb-uart-node-y +=3D gb_uart_node.o >> > > + >> > > +# Export Rust symbols from gb-softsvc only if gb-uart-node actually= references them. >> > > +gb-softsvc-export-deps :=3D $(if $(CONFIG_GREYBUS_UART_NODE),$(obj)= /gb_uart_node.o) >> > > + >> > > +rust_needed_exports =3D \ >> > > + { $(if $(strip $(2)),$(NM) -u $(2);,) echo "__DEFINED_RUST_SYMBOLS= __"; \ >> > > + $(NM) -p --defined-only $(1); } | \ >> > > + awk -v fmt=3D'$(3)' ' \ >> > > + /^__DEFINED_RUST_SYMBOLS__$$/ { defs =3D 1; next } \ >> > > + !defs { if ($$NF ~ /^_R/) needed[$$NF] =3D 1; next } \ >> > > + defs && $$2 ~ /(T|R|D|B)/ && $$3 ~ /^_R/ && \ >> > > + $$3 !~ /_(init|cleanup)_module$$/ && \ >> > > + $$3 !~ /__(pfx|cfi|odr_asan)/ && \ >> > > + $$3 in needed { printf fmt, $$3 } \ >> > > + ' >> > > + >> > > +quiet_cmd_exports =3D EXPORTS $@ >> > > + cmd_exports =3D \ >> > > + $(call rust_needed_exports,$<,$(gb-softsvc-export-deps),EXPORT_SYM= BOL_RUST_GPL(%s);\n) > $@ >> > > + >> > > +$(obj)/exports_gb_softsvc_generated.h: $(obj)/gb_softsvc.o $(gb-sof= tsvc-export-deps) FORCE >> > > + $(call if_changed,exports) >> > > + >> > > +targets +=3D exports_gb_softsvc_generated.h >> > > + >> > > +$(obj)/gb_softsvc_exports.o: $(obj)/exports_gb_softsvc_generated.h >> > > +CFLAGS_gb_softsvc_exports.o :=3D -I $(objtree)/$(obj) >> > > + >> > > +ifdef CONFIG_MODVERSIONS >> > > +# The C export shim declares Rust symbols as `extern int`, so reuse= its export >> > > +# list but generate symbol CRCs from the Rust object instead of the= shim's DWARF. >> > > +$(obj)/gb_softsvc_exports.o: private cmd_gensymtypes_c =3D \ >> > > + $(call getexportsymbols,\1) | \ >> > > + $(objtree)/scripts/gendwarfksyms/gendwarfksyms \ >> > > + $(if $(KBUILD_GENDWARFKSYMS_STABLE), --stable) \ >> > > + $(if $(KBUILD_SYMTYPES), --symtypes $(@:.o=3D.symtypes),) \ >> > > + $(obj)/gb_softsvc.o >> > > +endif >> > > + >> > > +# Output nova-core's crate metadata for use by nova-drm at compile = time. >> > > +RUSTFLAGS_gb_softsvc.o +=3D \ >> > > + --emit=3Dmetadata=3D$(objtree)/$(obj)/libgb_softsvc.rmeta >> > > + >> > > +# Allow nova-drm to import nova-core's types. >> > > +$(obj)/gb_uart_node.o: $(obj)/gb_softsvc.o >> > > +RUSTFLAGS_gb_uart_node.o :=3D -L $(objtree)/$(obj) --extern gb_soft= svc >> > > diff --git a/drivers/greybus/gb_uart_node.rs b/drivers/greybus/gb_ua= rt_node.rs >> > > new file mode 100644 >> > > index 000000000000..3eb4f8ab3655 >> > > --- /dev/null >> > > +++ b/drivers/greybus/gb_uart_node.rs >> > > @@ -0,0 +1,245 @@ >> > > +// SPDX-License-Identifier: GPL-2.0 >> > > + >> > > +//! Greybus UART Node driver >> > > + >> > > +use kernel::{ >> > > + alloc::Flags, >> > > + crc_ccitt::crc_ccitt, >> > > + device::{ >> > > + AsBusDevice, >> > > + Bound, >> > > + Core, // >> > > + }, >> > > + error::code, >> > > + new_spinlock, of, >> > > + prelude::*, >> > > + serdev, >> > > + sync::{ >> > > + aref::ARef, >> > > + Arc, >> > > + SpinLock, // >> > > + }, >> > > +}; >> > > + >> > > +use zerocopy::little_endian; >> > > +use zerocopy_derive::{FromBytes, Immutable, KnownLayout}; >> > > + >> > > +const HDLC_MAX_FRAME_LEN: usize =3D 256; >> > > + >> > > +const HDLC_FRAME: u8 =3D 0x7E; >> > > +const HDLC_ESC: u8 =3D 0x7D; >> > > +const HDLC_XOR: u8 =3D 0x20; >> > > +const HDLC_EXPECTED_CRC: u16 =3D 0xf0b8; >> > > + >> > > +const ADDRESS_GREYBUS: u8 =3D 0x01; >> > > + >> > > +#[repr(C, packed)] >> > > +#[derive(FromBytes, Immutable, KnownLayout)] >> > > +struct GreybusFrame { >> > > + cport: little_endian::U16, >> > > + msg: [u8], >> > > +} >> > > + >> > > +struct HdlcRx { >> > > + rx_buf: KVec, >> > > + rx_in_esc: bool, >> > > + sdev: ARef, >> > > + node: gb_softsvc::Module, >> > > +} >> > > + >> > > +impl HdlcRx { >> > > + fn new(sdev: ARef, node: gb_softsvc::Module) ->= Result { >> > > + Ok(Self { >> > > + node, >> > > + sdev, >> > > + rx_buf: KVec::with_capacity(HDLC_MAX_FRAME_LEN, GFP_KER= NEL)?, >> > > + rx_in_esc: false, >> > > + }) >> > > + } >> > > + >> > > + fn frame_finish(&self) -> Result<()> { >> > > + if self.rx_buf.len() < 4 { >> > > + return Err(code::EFAULT); >> > > + } >> > > + >> > > + let crc =3D crc_ccitt(0xffff, &self.rx_buf); >> > > + if crc !=3D HDLC_EXPECTED_CRC { >> > > + dev_warn!(self.sdev.as_ref(), "CRC failed {}", crc); >> > > + return Ok(()); >> > > + } >> > > + >> > > + let addr =3D self.rx_buf[0]; >> > > + let _ctrl =3D self.rx_buf[1]; >> > > + let payload =3D &self.rx_buf[2..self.rx_buf.len() - size_of= ::()]; >> > > + >> > > + match addr { >> > > + ADDRESS_GREYBUS =3D> { >> > > + let frame =3D GreybusFrame::ref_from_bytes(payload)= .map_err(|_| code::EINVAL)?; >> > > + self.node.submit_message(0, frame.cport.into(), &fr= ame.msg) >> > > + } >> > > + _ =3D> Err(code::EINVAL), >> > > + } >> > > + } >> > > + >> > > + fn rx(&mut self, data: &[u8]) -> usize { >> > > + for i in data.iter() { >> > > + match *i { >> > > + HDLC_FRAME =3D> { >> > > + if !self.rx_buf.is_empty() { >> > > + if let Err(e) =3D self.frame_finish() { >> > > + dev_warn!(self.sdev.as_ref(), "bad fram= e: {e:?}\n"); >> > > + } >> > > + } >> > > + >> > > + self.rx_buf.clear(); >> > > + self.rx_in_esc =3D false; >> > > + } >> > > + HDLC_ESC =3D> self.rx_in_esc =3D true, >> > > + _ =3D> { >> > > + let c =3D if self.rx_in_esc { *i ^ HDLC_XOR } e= lse { *i }; >> > > + self.rx_in_esc =3D false; >> > > + >> > > + if self.rx_buf.push_within_capacity(c).is_err()= { >> > > + dev_warn!(self.sdev.as_ref(), "buffer overf= low. Dropping frame"); >> > > + >> > > + self.rx_buf.clear(); >> > > + self.rx_in_esc =3D false; >> > > + } >> > > + } >> > > + } >> > > + } >> > > + >> > > + data.len() >> > > + } >> > > +} >> > > + >> > > +struct GbNode { >> > > + sdev: ARef, >> > > +} >> > > + >> > > +impl GbNode { >> > > + const fn new(sdev: ARef) -> Self { >> > > + Self { sdev } >> > > + } >> > > + >> > > + fn fill_buf(mut crc: u16, data: &[u8], buf: &mut KVec) -> R= esult { >> > > + for i in data { >> > > + crc =3D crc_ccitt(crc, &[*i]); >> > > + if *i =3D=3D HDLC_ESC || *i =3D=3D HDLC_FRAME { >> > > + buf.push_within_capacity(HDLC_ESC)?; >> > > + buf.push_within_capacity(i ^ HDLC_XOR)?; >> > > + } else { >> > > + buf.push_within_capacity(*i)?; >> > > + } >> > > + } >> > > + >> > > + Ok(crc) >> > > + } >> > > +} >> > > + >> > > +impl gb_softsvc::InterfaceOps for GbNode { >> > > + fn write(&self, data: &[u8], cport: u16, gfp_mask: Flags) -> Re= sult<()> { >> > > + // SAFETY: `GbNode` only exists while its serdev driver is = bound, so the device is in the >> > > + // `Bound` state for the duration of this call. >> > > + let bound: &serdev::Device =3D >> > > + unsafe { serdev::Device::from_device(self.sdev.as_ref()= .as_bound()) }; >> > > + >> > > + let mut buf =3D KVec::with_capacity(HDLC_MAX_FRAME_LEN, gfp= _mask)?; >> > > + >> > > + let mut crc =3D 0xffff; >> > > + >> > > + buf.push_within_capacity(HDLC_FRAME)?; >> > > + >> > > + crc =3D Self::fill_buf(crc, &[ADDRESS_GREYBUS, 0x03], &mut = buf)?; >> > > + crc =3D Self::fill_buf(crc, &cport.to_le_bytes(), &mut buf)= ?; >> > > + crc =3D Self::fill_buf(crc, data, &mut buf)?; >> > > + >> > > + crc ^=3D 0xffff; >> > > + Self::fill_buf(crc, &crc.to_le_bytes(), &mut buf)?; >> > > + >> > > + buf.push_within_capacity(HDLC_FRAME)?; >> > > + >> > > + bound.write_all(&buf, 0)?; >> > > + >> > > + Ok(()) >> > > + } >> > > +} >> > > + >> > > +#[pin_data] >> > > +struct GbUartNode { >> > > + #[pin] >> > > + rx: SpinLock>, >> > (add me to CC please) >> >=20 >> > Instead of using a lock here, it might be a better idea to >> > synchronize/stop the receive callback before unbind is called in the >> > serdev rust abstraction. This would allow the abstraction to provide >> > mutable references to the driver data in `receive` and `unbind`. It >> > would also remove the Sync requirement. >> >=20 >> > I will send a patch soon. >> >=20 >> > Thanks >> > - Markus Probst >>=20 >> That sounds great. The lock here was basically only for getting a mut=20 >> ref. I will base the next version on top of your patches. >>=20 >> I have added your email for the next patch version. > It appears that "would break the driver core's lifetime design", so I > have to drop the patch. > > You will still need the SpinLock. You can still do sychronization to allow this, just not using things from drvdata. For example, if you move this "active: Mutex" to be part of `serdev_device`, then you don't need to access `drvdata` to set the active field. That'll be actually more inline with what other buses are doing, where drvd= ata is exclusively for the drivers, and for the bus. Best, Gary