Implement core serial routines

This is just a rough baseline for the higher-level
serial handling code and will probably change
within the next couple of commits.

arch/at91sam3x8e/Makefile

@@ -27,6 +27,7 @@ ARDIX_ARCH_PWD = $(PWD)/arch/at91sam3x8e
 
 ARDIX_SOURCES += \
 	$(ARDIX_ARCH_PWD)/sched.c \
+	$(ARDIX_ARCH_PWD)/serial.c \
 	$(ARDIX_ARCH_PWD)/startup.c \
 	$(ARDIX_ARCH_PWD)/sys.c
 

arch/at91sam3x8e/serial.c

@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/* See the end of this file for copyright, licensing, and warranty information. */
+
+#include <ardix/serial.h>
+#include <ardix/types.h>
+#include <ardix/ringbuf.h>
+
+#include <arch/hardware.h>
+#include <arch/serial.h>
+
+int arch_serial_init(struct serial_interface *interface)
+{
+	/* TODO */
+	return -1;
+}
+
+void arch_serial_exit(struct serial_interface *interface)
+{
+	/* TODO */
+}
+
+int arch_serial_op_begin(struct serial_interface *interface)
+{
+	/* TODO */
+	return -1;
+}
+
+ssize_t arch_serial_op_read(struct serial_interface *interface)
+{
+	/* TODO */
+	return 0;
+}
+
+ssize_t arch_serial_op_write(struct serial_interface *interface)
+{
+	/* TODO */
+	return 0;
+}
+
+struct serial_operations arch_serial_operations = {
+	.begin = &arch_serial_op_begin,
+	.read = &arch_serial_op_read,
+	.write = &arch_serial_op_write,
+};
+
+/*
+ * Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
+ *
+ * Redistribution and use in source and binary forms, with or without modification, are permitted
+ * provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
+ *    conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
+ * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */

include/arch/at91sam3x8e/serial.h

@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/* See the end of this file for copyright, licensing, and warranty information. */
+
+#pragma once
+
+#include <ardix/serial.h>
+
+/*
+ * Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
+ *
+ * Redistribution and use in source and binary forms, with or without modification, are permitted
+ * provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
+ *    conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
+ * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */

include/arch/serial.h

@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/* See the end of this file for copyright, licensing, and warranty information. */
+
+#pragma once
+
+#include <ardix/serial.h>
+
+extern struct serial_operations arch_serial_operations;
+
+int arch_serial_init(struct serial_interface *interface);
+void arch_serial_exit(struct serial_interface *interface);
+
+#ifdef ARCH_AT91SAM3X8E
+#include <arch/at91sam3x8e/serial.h>
+#else
+#error "Unsupported architecture"
+#endif
+
+/*
+ * Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
+ *
+ * Redistribution and use in source and binary forms, with or without modification, are permitted
+ * provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
+ *    conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
+ * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */

include/ardix/serial.h

@@ -7,20 +7,28 @@
 #include <ardix/ringbuf.h>
 #include <toolchain.h>
 
+#ifndef SERIAL_BUFSZ
+/** size of a serial I/O buffer in bytes */
+#define SERIAL_BUFSZ 64
+#endif
+
+struct serial_interface;
+
 /** Low-level hardware operations implemented by the serial driver. */
 struct serial_operations {
-	/** Begin transmission at the specified baud rate. */
+	/** Do any hardware setup required to transmit data. */
-	int (*begin)(struct serial_interface *serial, long int baud);
+	int (*begin)(struct serial_interface *serial);
 	/** Read from the hardware input buffer and store it into the rx ring buffer */
-	ssize_t (*read)(uint8_t *dest, struct serial_interface *serial, size_t len);
+	ssize_t (*read)(struct serial_interface *serial);
 	/** Read from the tx ring buffer and store it into the hardware output buffer */
-	ssize_t (*write)(struct serial_interface *serial, const uint8_t *src, size_t len);
+	ssize_t (*write)(struct serial_interface *serial);
 };
 
 struct serial_interface {
 	struct ringbuf *rx;
 	struct ringbuf *tx;
 	long int baud;
+	int id;
 	struct serial_operations operations;
 };
 
@@ -32,10 +40,9 @@ extern struct serial_interface *serial_default_interface;
  *
  * @param interface: The serial interface.
  * @param baud: The baud rate (bits/second).
- * @param buflen: The respective length of the read and write buffer.
  * @returns 0 on success, a negative number otherwise.
  */
-int serial_init(struct serial_interface *interface, long int baud, size_t buflen);
+int serial_init(struct serial_interface *interface, long int baud);
 
 /**
  * Flush all buffers (if possible) and close the serial interface.

kernel/Makefile

@@ -27,4 +27,5 @@ ARDIX_KERNEL_PWD = $(PWD)/kernel
 
 ARDIX_SOURCES += \
 	$(ARDIX_KERNEL_PWD)/ringbuf.c \
-	$(ARDIX_KERNEL_PWD)/sched.c
+	$(ARDIX_KERNEL_PWD)/sched.c \
+	$(ARDIX_KERNEL_PWD)/serial.c

kernel/serial.c

@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/* See the end of this file for copyright, licensing, and warranty information. */
+
+#include <ardix/ringbuf.h>
+#include <ardix/serial.h>
+
+#include <arch/serial.h>
+
+#include <stddef.h>
+
+int serial_init(struct serial_interface *interface, long int baud)
+{
+	int err = -1;
+
+	if (interface->id < 0)
+		return -1; /* invalid interface */
+
+	interface->baud = baud;
+
+	interface->rx = ringbuf_create(SERIAL_BUFSZ);
+	if (interface->rx == NULL)
+		return -1;
+
+	interface->tx = ringbuf_create(SERIAL_BUFSZ);
+	if (interface->tx == NULL) {
+		ringbuf_destroy(interface->rx);
+		return -1;
+	}
+
+	err = arch_serial_init(interface);
+	if (err) {
+		ringbuf_destroy(interface->rx);
+		ringbuf_destroy(interface->tx);
+	}
+
+	return err;
+}
+
+void serial_exit(struct serial_interface *interface)
+{
+	arch_serial_exit(interface);
+	ringbuf_destroy(interface->rx);
+	ringbuf_destroy(interface->tx);
+	interface->id = -1;
+}
+
+/* TODO: tell the scheduler to run the I/O thread next after these calls */
+
+ssize_t serial_read(uint8_t *dest, struct serial_interface *interface, size_t len)
+{
+	return (ssize_t)ringbuf_read(dest, interface->rx, len);
+}
+
+ssize_t serial_write(struct serial_interface *interface, const uint8_t *data, size_t len)
+{
+	return (ssize_t)ringbuf_write(interface->tx, data, len);
+}
+
+/*
+ * Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
+ *
+ * Redistribution and use in source and binary forms, with or without modification, are permitted
+ * provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
+ *    conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
+ * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */