linux-kernel - Re: [patch 25/29] xen: Add the Xen virtual network device driver.

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Message-Id: <1178577322.28438.16.camel@localhost.localdomain>
Date:	Tue, 08 May 2007 08:35:22 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Christoph Hellwig <hch@...radead.org>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	virtualization@...ts.osdl.org, lkml <linux-kernel@...r.kernel.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Ian Pratt <ian.pratt@...source.com>,
	Christian Limpach <Christian.Limpach@...cam.ac.uk>,
	netdev@...r.kernel.org, Jeff Garzik <jeff@...zik.org>,
	Stephen Hemminger <shemminge@...ux-foundation.org>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [patch 25/29] xen: Add the Xen virtual network device driver.

On Mon, 2007-05-07 at 14:11 -0700, Jeremy Fitzhardinge wrote:
> Christoph Hellwig wrote:
> > On Fri, May 04, 2007 at 04:21:16PM -0700, Jeremy Fitzhardinge wrote:
> >   
> >> +/*
> >> + * Mutually-exclusive module options to select receive data path:
> >> + *  rx_copy : Packets are copied by network backend into local memory
> >> + *  rx_flip : Page containing packet data is transferred to our ownership
> >> + * For fully-virtualised guests there is no option - copying must be used.
> >> + * For paravirtualised guests, flipping is the default.
> >> + */
> >> +static enum {
> >> +	RX_COPY = 0,
> >> +	RX_FLIP = 1,
> >> +} rx_mode = RX_FLIP;
> >> +MODULE_PARM_DESC(rx_mode, "How to get packets from card: 0->copy, 1->flip");
> >>     
> >
> > There only seems to be a module description but no actual paramter for
> > this.  I wish people would have listened to me back then and made the
> > description part of the modular_param statement..
> 
> Is this correct?
> 
> ---
>  drivers/net/xen-netfront.c |   32 ++++++++++++++++++++++++++++----
>  1 file changed, 28 insertions(+), 4 deletions(-)
> 
> ===================================================================
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -62,16 +62,40 @@ struct netfront_cb {
>  
>  /*
>   * Mutually-exclusive module options to select receive data path:
> - *  rx_copy : Packets are copied by network backend into local memory
> - *  rx_flip : Page containing packet data is transferred to our ownership
> + *  copy : Packets are copied by network backend into local memory
> + *  flip : Page containing packet data is transferred to our ownership
>   * For fully-virtualised guests there is no option - copying must be used.
>   * For paravirtualised guests, flipping is the default.
>   */
> -static enum {
> +static enum rx_mode {
>  	RX_COPY = 0,
>  	RX_FLIP = 1,
>  } rx_mode = RX_FLIP;
> -MODULE_PARM_DESC(rx_mode, "How to get packets from card: 0->copy, 1->flip");
> +MODULE_PARM_DESC(rx_mode, "How to get packets from card: \"copy\" or \"flip\"");
> +
> +static int set_rx_mode(const char *val, struct kernel_param *kp)
> +{
> +	enum rx_mode *rxmp = kp->arg;
> +	int ret = 0;
> +
> +	if (strcmp(val, "copy") == 0)
> +		*rxmp = RX_COPY;
> +	else if (strcmp(val, "flip") == 0)
> +		*rxmp = RX_FLIP;
> +	else
> +		ret = -EINVAL;
> +
> +	return ret;
> +}
> +
> +static int get_rx_mode(char *buffer, struct kernel_param *kp)
> +{
> +	enum rx_mode *rxmp = kp->arg;
> +
> +	return sprintf(buffer, "%s", *rxmp == RX_COPY ? "copy" : "flip");
> +}
> +
> +module_param_call(rx_mode, set_rx_mode, get_rx_mode, &rx_mode, 0400);

Looks good, you can slightly improve it to be the model use of new
module_param types by calling your functions param_set_rx_mode and
param_get_rx_mode, then simply using "module_param(rx_mode, rx_mode,
0400)"

Cheers,
Rusty.


>  
>  #define RX_COPY_THRESHOLD 256
>  

-
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