linux-kernel - Re: [PATCH 2/2] usbnet: use MII hooks only if CONFIG

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Message-ID: <20061028112122.GA14316@infradead.org>
Date:	Sat, 28 Oct 2006 12:21:22 +0100
From:	Christoph Hellwig <hch@...radead.org>
To:	Randy Dunlap <randy.dunlap@...cle.com>
Cc:	David Brownell <david-b@...bell.net>, toralf.foerster@....de,
	netdev@...r.kernel.org, linux-usb-devel@...ts.sourceforge.net,
	link@...gy.org, greg@...ah.com, akpm@...l.org,
	zippel@...ux-m68k.org, torvalds@...l.org,
	linux-kernel@...r.kernel.org, dbrownell@...rs.sourceforge.net
Subject: Re: [PATCH 2/2] usbnet: use MII hooks only if CONFIG_MII is enabled

On Wed, Oct 25, 2006 at 04:58:58PM -0700, Randy Dunlap wrote:
> On Wed, 25 Oct 2006 15:27:09 -0700 David Brownell wrote:
> 
> > Instead, "usbnet.c" should #ifdef the relevant ethtool hooks
> > according to CONFIG_MII ... since it's completely legit to
> > use usbnet with peripherals that don't need MII.
> 
> ---
> From: Randy Dunlap <randy.dunlap@...cle.com>
> 
> usbnet driver should use mii_*() interfaces if they are available
> in the kernel (config enabled) but usbnet does not require or depend
> on these interfaces.
> 
> Build tested with CONFIG_MII=y, m, n.

This is really awkward and against what we do in any other driver.
Lots of PCI ethernet drivers use the MII code but have non-MII variants,
and I'd expect usb code to do the same.  If you really need to squeeze
the last bytes out of usbnet for some embedded thing add a CONFIG_USB_NET_MII
opention and explain in the help text which devices require it.  Otherwise
a normal user has no way to find out why his mii-requiring usb device
randomly stopped working.

> 
> Signed-off-by: Randy Dunlap <randy.dunlap@...cle.com>
> ---
>  drivers/usb/net/usbnet.c |   18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> --- linux-2619-rc3-pv.orig/drivers/usb/net/usbnet.c
> +++ linux-2619-rc3-pv/drivers/usb/net/usbnet.c
> @@ -47,6 +47,12 @@
>  
>  #define DRIVER_VERSION		"22-Aug-2005"
>  
> +#if defined(CONFIG_MII) || defined(CONFIG_MII_MODULE)
> +#define HAVE_MII		1
> +#else
> +#define HAVE_MII		0
> +#endif
> +
>  
>  /*-------------------------------------------------------------------------*/
>  
> @@ -676,7 +682,10 @@ int usbnet_get_settings (struct net_devi
>  	if (!dev->mii.mdio_read)
>  		return -EOPNOTSUPP;
>  
> +#if HAVE_MII
>  	return mii_ethtool_gset(&dev->mii, cmd);
> +#endif
> +	return -EOPNOTSUPP;
>  }
>  EXPORT_SYMBOL_GPL(usbnet_get_settings);
>  
> @@ -688,7 +697,11 @@ int usbnet_set_settings (struct net_devi
>  	if (!dev->mii.mdio_write)
>  		return -EOPNOTSUPP;
>  
> +#if HAVE_MII
>  	retval = mii_ethtool_sset(&dev->mii, cmd);
> +#else
> +	retval = -EOPNOTSUPP;
> +#endif
>  
>  	/* link speed/duplex might have changed */
>  	if (dev->driver_info->link_reset)
> @@ -721,9 +734,11 @@ u32 usbnet_get_link (struct net_device *
>  	if (dev->driver_info->check_connect)
>  		return dev->driver_info->check_connect (dev) == 0;
>  
> +#if HAVE_MII
>  	/* if the device has mii operations, use those */
>  	if (dev->mii.mdio_read)
>  		return mii_link_ok(&dev->mii);
> +#endif
>  
>  	/* Otherwise, say we're up (to avoid breaking scripts) */
>  	return 1;
> @@ -753,7 +768,10 @@ int usbnet_nway_reset(struct net_device 
>  	if (!dev->mii.mdio_write)
>  		return -EOPNOTSUPP;
>  
> +#if HAVE_MII
>  	return mii_nway_restart(&dev->mii);
> +#endif
> +	return -EOPNOTSUPP;
>  }
>  EXPORT_SYMBOL_GPL(usbnet_nway_reset);
>  
> -
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