linux-kernel - [PATCH 5/5] virtio: don't require a config space on the console device.

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Date:	Fri,  6 Feb 2015 15:36:56 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	"lkml" <linux-kernel@...r.kernel.org>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>,
	Amit Shah <amit.shah@...hat.com>
Subject: [PATCH 5/5] virtio: don't require a config space on the console device.

Strictly, it's only needed when we have features (size or multiport).

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
---
 drivers/char/virtio_console.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 26afb56a8073..8f182b0015b5 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1986,10 +1986,14 @@ static int virtcons_probe(struct virtio_device *vdev)
 	bool multiport;
 	bool early = early_put_chars != NULL;
 
-	if (!vdev->config->get) {
-		dev_err(&vdev->dev, "%s failure: config access disabled\n",
-			__func__);
-		return -EINVAL;
+	/* We only need a config space if features are offered */
+	if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE)
+	    || virtio_has_feature(vdev, VIRTIO_CONSOLE_F_MULTIPORT)) {
+		if (!vdev->config->get) {
+			dev_err(&vdev->dev, "%s failure: config access disabled\n",
+				__func__);
+			return -EINVAL;
+		}
 	}
 
 	/* Ensure to read early_put_chars now */
-- 
2.1.0

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