drivers: ppp: Move to DTS for uart device

Move from using Kconfig NET_PPP_UART_NAME to a devicetree chosen
property ("zephyr,ppp-uart").  This is similar to a number of other
functions like "zephyr,shell-uart" or "zephyr,bt-uart".

As part of this we rework the init code a little to use
DEVICE_DT_GET for the modem gsm-ppp case.

Signed-off-by: Kumar Gala <[email protected]>

Author: galak

doc/build/dts/api/api.rst

@@ -422,6 +422,8 @@ device.
      - Used by the OpenThread to specify UART device for Spinel protocol
    * - zephyr,pcie-controller
      - The node corresponding to the PCIe Controller
+   * - zephyr,ppp-uart
+     - Sets UART device used by PPP
    * - zephyr,settings-partition
      - Fixed partition node. If defined this selects the partition used
        by the NVS and FCB settings backends.

drivers/net/Kconfig

@@ -23,10 +23,6 @@ config NET_PPP_ASYNC_UART
 	depends on UART_ASYNC_API
 	depends on !GSM_MUX
 
-config NET_PPP_UART_NAME
-	string "UART device name the PPP is connected to"
-	depends on !MODEM_GSM_PPP
-
 config NET_PPP_DRV_NAME
 	string "PPP Driver name"
 	default "ppp"

drivers/net/ppp.c

@@ -1018,8 +1018,6 @@ static int ppp_start(const struct device *dev)
 	 */
 #if !defined(CONFIG_NET_TEST)
 	if (atomic_cas(&context->modem_init_done, false, true)) {
-		const char *dev_name = NULL;
-
 		/* Now try to figure out what device to open. If GSM muxing
 		 * is enabled, then use it. If not, then check if modem
 		 * configuration is enabled, and use that. If none are enabled,
@@ -1035,22 +1033,17 @@ static int ppp_start(const struct device *dev)
 			return -ENOENT;
 		}
 
-		dev_name = mux->name;
+		context->dev = mux;
 #elif IS_ENABLED(CONFIG_MODEM_GSM_PPP)
-		dev_name = DT_BUS_LABEL(DT_INST(0, zephyr_gsm_ppp));
+		context->dev = DEVICE_DT_GET(DT_BUS(DT_INST(0, zephyr_gsm_ppp)));
 #else
-		dev_name = CONFIG_NET_PPP_UART_NAME;
+		/* dts chosen zephyr,ppp-uart case */
+		context->dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_ppp_uart));
 #endif
-		if (dev_name == NULL || dev_name[0] == '\0') {
-			LOG_ERR("UART configuration is wrong!");
-			return -EINVAL;
-		}
-
-		LOG_INF("Initializing PPP to use %s", dev_name);
+		LOG_INF("Initializing PPP to use %s", context->dev->name);
 
-		context->dev = device_get_binding(dev_name);
-		if (!context->dev) {
-			LOG_ERR("Cannot find dev %s", dev_name);
+		if (!device_is_ready(context->dev)) {
+			LOG_ERR("Device %s is not ready", context->dev->name);
 			return -ENODEV;
 		}
 #if defined(CONFIG_NET_PPP_ASYNC_UART)