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Subject[PATCH v1 1/3] dt-bindings: ttyvs: document serial null modem driver dt bindings
Date
The ttyvs driver creates virtual tty devices. These devices can
also be created through device tree. This commit document this.

Signed-off-by: Rishi Gupta <gupt21@gmail.com>
---
.../devicetree/bindings/serial/ttyvs.yaml | 175 +++++++++++++++++++++
1 file changed, 175 insertions(+)
create mode 100644 Documentation/devicetree/bindings/serial/ttyvs.yaml

diff --git a/Documentation/devicetree/bindings/serial/ttyvs.yaml b/Documentation/devicetree/bindings/serial/ttyvs.yaml
new file mode 100644
index 0000000..d37c237
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/ttyvs.yaml
@@ -0,0 +1,175 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/serial/ttyvs.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Virtual multi-port serial card DT bindings
+
+maintainers:
+ - Rishi Gupta <gupt21@gmail.com>
+
+description: |
+ The ttyvs driver creates a virtual card accessible through node
+ /dev/ttyvs_card. This card can have 0 to 65535 virtual tty devices.
+ The card is modeled as a node with zero or more child nodes each
+ representing a virtual tty device. These devices can be configured
+ to be a loop-back type device or it can be part of a null-modem pair.
+
+ Devices can be created through DT (see examples Ex1/2/3 at the end)
+ or by writing pre-formatted string to card node.
+
+ If the driver is built as loadable module, standard null modem pairs
+ can be created by passing 'init_num_nm_pairs' parameter. Similarly,
+ standard loopback devices can be created by passing 'init_num_lb_devs'
+ parameter. When DT is used and device nodes are defined, all devices
+ created due to module parameters will be deleted first and then
+ devices specified by DT will be created.
+
+ Devices can be deleted only by writing pre-formatted string to card node,
+ irrespective of whether they were created using DT or through string.
+
+properties:
+ compatible:
+ const: ttyvs,virtual-uart-card
+
+ max-num-vs-devs:
+ allOf:
+ - $ref: /schemas/types.yaml#/definitions/uint32
+ - minimum: 0
+ - maximum: 0xffff
+ maxItems: 1
+ description:
+ By default, the driver can create upto 64 devices. This number can
+ be changed by passing 'max_num_vs_devs' parameter to the driver or
+ by defining 'max-num-vs-devs' DT property. If both are used then
+ first all devices created during module loading are deleted, then
+ driver updates itself to support total number of devices as defined
+ by max-num-vs-devs property.
+
+patternProperties:
+ "^ttyvs@[0-9]+$":
+ type: object
+ description:
+ A node representing one virtual tty device. This node optionally,
+ describes, device number and its configuration.
+
+ properties:
+ dev-num:
+ allOf:
+ - $ref: /schemas/types.yaml#/definitions/uint32
+ - minimum: 0
+ - maximum: 0xffff
+ maxItems: 1
+ description:
+ Specifies index (N in /dev/ttyvsN) to use for creating device.
+ If this property is not specified then next lowest free index
+ is used by driver. Valid value for N is 0 to 65535.
+
+ rtsmap:
+ allOf:
+ - $ref: /schemas/types.yaml#/definitions/uint32-array
+ items:
+ - enum: [1, 6, 8, 9]
+ maxItems: 1
+ description:
+ Specifies to which pin(s) RTS pin of this device should be
+ connected. Valid values are pin 1 (DCD), pin 6 (DSR), pin 8
+ (CTS) and pin 9 (RI). If this is not used then RTS pin is
+ left unconnected.
+
+ dtrmap:
+ allOf:
+ - $ref: /schemas/types.yaml#/definitions/uint32-array
+ items:
+ - enum: [1, 6, 8, 9]
+ maxItems: 1
+ description:
+ Specifies to which pin(s) DTR pin of this device should be
+ connected. Valid values are pin 1 (DCD), pin 6 (DSR), pin 8
+ (CTS) and pin 9 (RI). If this is not used then DTR pin is
+ left unconnected.
+
+ set-dtr-at-open:
+ type: boolean
+ description:
+ If used, DTR signal will be asserted by driver when device
+ node is opened by user space application.
+
+ peer-dev:
+ $ref: /schemas/types.yaml#definitions/phandle
+ description:
+ Phandle to the peer DT node if this node is part of a null
+ modem pair.
+
+required:
+ - compatible
+
+examples:
+ - |
+ # Ex1; Null-modem pair only TX/RX connected
+ # /dev/ttvs0 <---> /dev/ttyvs1
+ # TX (3) ----> (2) RX
+ # RX (2) <---- (3) TX
+
+ ttyvs-card@0 {
+ compatible = "ttyvs,virtual-uart-card";
+
+ ttyvs0: ttyvs0 {
+ dev-num = <0>;
+ peer-dev = <&ttyvs1>;
+ };
+
+ ttyvs1: ttyvs1 {
+ dev-num = <1>;
+ peer-dev = <&ttyvs0>;
+ };
+ };
+
+ - |
+ # Ex2; Standard loop-back device
+ # TX (3) -->|
+ # RX (2) <--|
+
+ ttyvs-card@0 {
+ compatible = "ttyvs,virtual-uart-card";
+ ttyvs2 {
+ dev-num = <2>;
+ rtsmap = <8>;
+ dtrmap = <1 6>;
+ set-dtr-at-open;
+ };
+ };
+
+ - |
+ # Ex3; Standard null-modem pair for hardware flow control
+ # TX (3) ----> (2) RX
+ # RX (2) <---- (3) TX
+ # RTS (7) ----> (8) CTS
+ # DTR (4) --+-> (1) DCD
+ # +-> (6) DSR
+ # CTS (8) <---- (7) RTS
+ # DCD (1) <-+-- (4) DTR
+ # DSR (6) <-+
+
+ ttyvs-card@0 {
+ compatible = "ttyvs,virtual-uart-card";
+ max-num-vs-devs = <128>;
+
+ ttyvs3: ttyvs3 {
+ dev-num = <3>;
+ rtsmap = <8>;
+ dtrmap = <1 6>;
+ set-dtr-at-open;
+ peer-dev = <&ttyvs4>;
+ };
+
+ ttyvs4: ttyvs4 {
+ dev-num = <4>;
+ rtsmap = <8>;
+ dtrmap = <1 6>;
+ set-dtr-at-open;
+ peer-dev = <&ttyvs3>;
+ };
+ };
+...
--
2.7.4
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