Add example implementation of a trivial blocking read function as a
part of Barebox's serdev API.
NOTE: This code has not been tested against real devices, so use it at
your own risk.
Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
---
common/serdev.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
include/serdev.h | 8 +++++
2 files changed, 103 insertions(+)
diff --git a/common/serdev.c b/common/serdev.c
index 32743738e..50eadc804 100644
--- a/common/serdev.c
+++ b/common/serdev.c
@@ -87,3 +87,98 @@ int serdev_device_write(struct serdev_device *serdev, const unsigned char *buf,
serdev_device_poller(serdev);
return 0;
}
+
+/*
+ * NOTE: Code below is given primarily as an example of serdev API
+ * usage. It may or may not be as useful or work as well as the
+ * functions above.
+ */
+
+struct serdev_device_reader {
+ unsigned char *buf;
+ size_t len;
+ size_t capacity;
+};
+
+static int serdev_device_reader_receive_buf(struct serdev_device *serdev,
+ const unsigned char *buf,
+ size_t size)
+{
+ struct device_d *dev = serdev->dev;
+ struct serdev_device_reader *r = dev->priv;
+ const size_t room = min(r->capacity - r->len, size);
+
+ memcpy(r->buf + r->len, buf, room);
+ r->len += room;
+ /*
+ * It's important we return 'size' even if we didn't trully
+ * consume all of the data, since otherwise serdev will keep
+ * re-executing us until we do. Given the logic above that
+ * would mean infinite loop.
+ */
+ return size;
+}
+
+/**
+ * serdev_device_reader_open - Open a reader serdev device
+ *
+ * @serdev: Underlying serdev device
+ * @capacity: Storage capacity of the reader
+ *
+ * This function is inteded for creating of reader serdev devices that
+ * can be used in conjunction with serdev_device_read() to perform
+ * trivial fixed length reads from a serdev device.
+ */
+int serdev_device_reader_open(struct serdev_device *serdev, size_t capacity)
+{
+ struct serdev_device_reader *r;
+
+ if (serdev->receive_buf)
+ return -EINVAL;
+
+ r = xzalloc(sizeof(*r));
+ r->capacity = capacity;
+ r->buf = xzalloc(capacity);
+
+ serdev->receive_buf = serdev_device_reader_receive_buf;
+ serdev->dev->priv = r;
+
+ return 0;
+}
+
+/**
+ * serdev_device_read - Read data from serdev device
+ *
+ * @serdev: Serdev device to read from (must be a serdev reader)
+ * @buf: Buffer to read data into
+ * @count: Number of bytes to read
+ * @timeout: Read operation timeout
+ *
+ */
+int serdev_device_read(struct serdev_device *serdev, unsigned char *buf,
+ size_t count, unsigned long timeout)
+{
+ struct device_d *dev = serdev->dev;
+ struct serdev_device_reader *r = dev->priv;
+ int ret;
+
+ uint64_t start = get_time_ns();
+
+ if (serdev->receive_buf != serdev_device_reader_receive_buf)
+ return -EINVAL;
+
+ /*
+ * is_timeout will implicitly poll serdev via poller
+ * infrastructure
+ */
+ while (r->len < count) {
+ if (is_timeout(start, timeout))
+ return -ETIMEDOUT;
+ }
+
+ memcpy(buf, r->buf, count);
+ ret = (r->len == count) ? 0 : -EMSGSIZE;
+ r->len = 0;
+
+ return ret;
+}
diff --git a/include/serdev.h b/include/serdev.h
index efc735fed..f5d34f527 100644
--- a/include/serdev.h
+++ b/include/serdev.h
@@ -33,4 +33,12 @@ int serdev_device_open(struct serdev_device *);
unsigned int serdev_device_set_baudrate(struct serdev_device *, unsigned int);
int serdev_device_write(struct serdev_device *, const unsigned char *,
size_t, unsigned long);
+
+/*
+ * The following two functions are not a part of original Linux API
+ */
+int serdev_device_reader_open(struct serdev_device *, size_t);
+int serdev_device_read(struct serdev_device *, unsigned char *,
+ size_t, unsigned long);
+
#endif
--
2.14.3
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