[PATCH XTF v4] Implement pv_read_some

[Felix Schmoll <eggi.innovations@gmail.com>]

Implement reading from PV console. Making use of polling.

Signed-off-by: Felix Schmoll <eggi.innovations@gmail.com>

---
Changed since v3:
 * Add to comment: read function blocks if no data available
---
 common/console.c      | 26 ++++++++++++++++++++++++++
 include/xtf/console.h |  2 ++
 2 files changed, 28 insertions(+)

diff --git a/common/console.c b/common/console.c
index 7cb2361..b1a35f4 100644
--- a/common/console.c
+++ b/common/console.c
@@ -46,6 +46,32 @@ static size_t pv_console_write_some(const char *buf, size_t len)
 }
 
 /*
+ * Read out data from the pv ring, either until buffer is filled or no
+ * more data are available. Might result in partial strings, depending
+ * on how xenconsoled passes in data.
+ *
+ * Will block if no data are available.
+ */
+size_t pv_console_read_some(char *buf, size_t len)
+{
+    size_t s = 0;
+    uint32_t cons, prod;
+
+    while ( !test_and_clear_bit(pv_evtchn, shared_info.evtchn_pending) ||
+            (pv_ring->in_cons == pv_ring->in_prod) )
+        hypercall_poll(pv_evtchn);
+
+    cons = pv_ring->in_cons, prod = LOAD_ACQUIRE(&pv_ring->in_prod);
+
+    while ( (s < len) && (0 < (prod - cons)) )
+        buf[s++] = pv_ring->in[cons++ & (sizeof(pv_ring->in) - 1)];
+
+    STORE_RELEASE(&pv_ring->in_cons, cons);
+
+    return s;
+}
+
+/*
  * Write some data into the pv ring, synchronously waiting for all data to be
  * consumed.
  */
diff --git a/include/xtf/console.h b/include/xtf/console.h
index 2a93c06..caec790 100644
--- a/include/xtf/console.h
+++ b/include/xtf/console.h
@@ -25,6 +25,8 @@ void init_pv_console(xencons_interface_t *ring,
 void vprintk(const char *fmt, va_list args) __printf(1, 0);
 void printk(const char *fmt, ...) __printf(1, 2);
 
+size_t pv_console_read_some(char *buf, size_t len);
+
 #endif /* XTF_CONSOLE_H */
 
 /*
-- 
2.11.0


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