linux-kernel - [PATCH] drivers/tty/hvc/hvc_tile.c: properly return -EAGAIN

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Date:	Tue, 5 May 2015 13:11:28 -0400
From:	Chris Metcalf <cmetcalf@...hip.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>
CC:	Chris Metcalf <cmetcalf@...hip.com>
Subject: [PATCH] drivers/tty/hvc/hvc_tile.c: properly return -EAGAIN

We were returning zero if no bytes could be written to the Tilera
hypervisor console device, but this causes the output to be truncated.
By returning -EAGAIN the tty hvc driver will come back and try again,
which gives the semantics we want, and avoids dropping console output.

Signed-off-by: Chris Metcalf <cmetcalf@...hip.com>
---
I have queued this in the tile tree as a tile-specific device, but
if someone would prefer to pick it up for a tty or tty/hvc tree,
that's fine too; just let me know.

 drivers/tty/hvc/hvc_tile.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/hvc/hvc_tile.c b/drivers/tty/hvc/hvc_tile.c
index 3f6cd3102db5..9da1e842bbe9 100644
--- a/drivers/tty/hvc/hvc_tile.c
+++ b/drivers/tty/hvc/hvc_tile.c
@@ -51,7 +51,8 @@ int tile_console_write(const char *buf, int count)
 			      _SIM_CONTROL_OPERATOR_BITS));
 		return 0;
 	} else {
-		return hv_console_write((HV_VirtAddr)buf, count);
+		/* Translate 0 bytes written to EAGAIN for hvc_console_print. */
+		return hv_console_write((HV_VirtAddr)buf, count) ?: -EAGAIN;
 	}
 }
 
-- 
2.1.2

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