linux-kernel - Re: [PATCH] xenbus: advertize control feature flags

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Date:   Mon, 10 Oct 2016 11:17:24 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Paul Durrant <paul.durrant@...rix.com>,
        linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        David Vrabel <david.vrabel@...rix.com>
Subject: Re: [PATCH] xenbus: advertize control feature flags

On 10/10/16 09:43, Paul Durrant wrote:
> The Xen docs specify several flags which a guest can set to advertize
> which values of the xenstore control/shutdown key it will recognize.
> This patch adds code to write all the relevant feature-flag keys.
> 
> Signed-off-by: Paul Durrant <paul.durrant@...rix.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: David Vrabel <david.vrabel@...rix.com>
> Cc: Juergen Gross <jgross@...e.com>
> ---
>  drivers/xen/manage.c | 45 +++++++++++++++++++++++++++++++++++----------
>  1 file changed, 35 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
> index e12bd36..86cf57c 100644
> --- a/drivers/xen/manage.c
> +++ b/drivers/xen/manage.c

> @@ -309,8 +311,31 @@ static struct notifier_block xen_reboot_nb = {
>  
>  static int setup_shutdown_watcher(void)
>  {
> +	static struct shutdown_handler *handler;
>  	int err;
>  
> +	for (handler = &shutdown_handlers[0]; handler->command; handler++) {
> +		const char *fmt = "feature-%s";
> +		int size;
> +		char *node;
> +
> +		if (!handler->flag)
> +			continue;
> +
> +		size = snprintf(NULL, 0, fmt, handler->command);
> +
> +		node = kmalloc(++size, GFP_KERNEL);
> +		if (!node) {
> +			pr_err("Failed to allocate feature flag\n");
> +			return -ENOMEM;
> +		}
> +
> +		(void) snprintf(node, size, fmt, handler->command);

One other nit: please us kasprintf() instead of open coding it.


Juergen