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

Rusty Russell
2007-05-07T22:35:55Z

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
>