From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cornelia Huck <cohuck@redhat.com>
Subject: Re: [RFC PATCH] virtio: add space for device features show
Date: Mon, 8 Jan 2018 13:50:37 +0100
Message-ID: <20180108135037.5f29c10b.cohuck@redhat.com>
References: <20171226133539.GA15965@localhost.didichuxing.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <virtualization-bounces@lists.linux-foundation.org>
In-Reply-To: <20171226133539.GA15965@localhost.didichuxing.com>
List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/virtualization>,
	<mailto:virtualization-request@lists.linux-foundation.org?subject=unsubscribe>
List-Archive: <http://lists.linuxfoundation.org/pipermail/virtualization/>
List-Post: <mailto:virtualization@lists.linux-foundation.org>
List-Help: <mailto:virtualization-request@lists.linux-foundation.org?subject=help>
List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/virtualization>,
	<mailto:virtualization-request@lists.linux-foundation.org?subject=subscribe>
Sender: virtualization-bounces@lists.linux-foundation.org
Errors-To: virtualization-bounces@lists.linux-foundation.org
To: weiping zhang <zhangweiping@didichuxing.com>
Cc: virtualization@lists.linux-foundation.org, mst@redhat.com
List-Id: virtualization@lists.linuxfoundation.org

On Tue, 26 Dec 2017 21:35:44 +0800
weiping zhang <zhangweiping@didichuxing.com> wrote:

> make features string more readable, add space every 8bit.
> example:
> 00101010 01110000 00000000 00001100
> 
> Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
> ---
>  drivers/virtio/virtio.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 59e36ef..d7d2db1 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -50,9 +50,12 @@ static ssize_t features_show(struct device *_d,
>  
>  	/* We actually represent this as a bitstring, as it could be
>  	 * arbitrary length in future. */
> -	for (i = 0; i < sizeof(dev->features)*8; i++)
> -		len += sprintf(buf+len, "%c",
> +	for (i = 0; i < sizeof(dev->features) * 8; i++) {
> +		len += sprintf(buf + len, "%c",
>  			       __virtio_test_bit(dev, i) ? '1' : '0');
> +		if (i % 8 == 7)
> +			len += sprintf(buf + len, " ");
> +	}
>  	len += sprintf(buf+len, "\n");
>  	return len;
>  }

This might break consumers of this attribute.

I think the better approach is to write a userspace tool that can do
additional helpful stuff (like decoding the feature bits).