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

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Message-ID: <20150208110336.GL3185@redhat.com>
Date:	Sun, 8 Feb 2015 12:03:37 +0100
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Amit Shah <amit.shah@...hat.com>
Subject: Re: [PATCH 5/5] virtio: don't require a config space on the console
 device.

On Fri, Feb 06, 2015 at 03:36:56PM +1030, Rusty Russell wrote:
> 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) {

I dislike nested ifs. How about
		if (!vdev->config->get && (
		    (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE)
		    || virtio_has_feature(vdev, VIRTIO_CONSOLE_F_MULTIPORT))

?


> +			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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