netdev - RE: [PATCH] [V3] net: emaclite: adding MDIO and phy lib support

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Date:	Tue, 9 Feb 2010 16:00:04 -0700
From:	John Linn <John.Linn@...inx.com>
To:	"John Williams" <john.williams@...alogix.com>
CC:	<netdev@...r.kernel.org>, <linuxppc-dev@...abs.org>,
	<jgarzik@...ox.com>, <grant.likely@...retlab.ca>,
	<jwboyer@...ux.vnet.ibm.com>,
	"Sadanand Mutyala" <sadanan@...inx.com>
Subject: RE: [PATCH] [V3] net: emaclite: adding MDIO and phy lib support

> -----Original Message-----
> From: John Williams [mailto:john.williams@...alogix.com]
> Sent: Tuesday, February 09, 2010 3:30 PM
> To: John Linn
> Cc: netdev@...r.kernel.org; linuxppc-dev@...abs.org; jgarzik@...ox.com; grant.likely@...retlab.ca;
> jwboyer@...ux.vnet.ibm.com; Sadanand Mutyala
> Subject: Re: [PATCH] [V3] net: emaclite: adding MDIO and phy lib support
> 
> Hi John,
> 
> Sorry If I'm painting bike-sheds here, just one tiny tweak might be in
> order to standardise your mutex_unlock exit path:
> 
> > +static int xemaclite_mdio_read(struct mii_bus *bus, int phy_id, int reg)
> > +{
> > +       struct net_local *lp = bus->priv;
> > +       u32 ctrl_reg;
> > +       u32 rc;
> > +
> > +       mutex_lock(&lp->mdio_mutex);
> > +
> > +       if (xemaclite_mdio_wait(lp)) {
> > +               mutex_unlock(&lp->mdio_mutex);
> > +               return -ETIMEDOUT;
> > +       }
> 
> [snip]
> 
> 
> > +       if (xemaclite_mdio_wait(lp)) {
> > +               mutex_unlock(&lp->mdio_mutex);
> > +               return -ETIMEDOUT;
> > +       }
> 
> [snip]
> 
> 
> > +       dev_dbg(&lp->ndev->dev,
> > +               "xemaclite_mdio_read(phy_id=%i, reg=%x) == %x\n",
> > +               phy_id, reg, rc);
> > +
> > +       return rc;
> 
> Can this be better expressed like this:
> 
> my_func() {
>   mutex_lock()
> ..
> 
>   if(some error) {
>     rc=-ETIMEDOUT;
>     goto out_unlock;
>   }
>   ...
> 
>   /* success path */
>   rc=0;
> ..
> out_unlock:
>   mutex_unlock()
>   return rc;
> }
> 
> 
> Is this style still favoured in driver exit paths?

It looks to me like the mutex is not needed in the driver mdio functions as there's a mutex in the mdiobus functions already.

Am I wrong about that?

Thanks,
John

>From phy/mdio_bus.c

int mdiobus_read(struct mii_bus *bus, int addr, u16 regnum)
{
	int retval;

	BUG_ON(in_interrupt());

	mutex_lock(&bus->mdio_lock);
	retval = bus->read(bus, addr, regnum);
	mutex_unlock(&bus->mdio_lock);

	return retval;
}
EXPORT_SYMBOL(mdiobus_read);

int mdiobus_write(struct mii_bus *bus, int addr, u16 regnum, u16 val)
{
	int err;

	BUG_ON(in_interrupt());

	mutex_lock(&bus->mdio_lock);
	err = bus->write(bus, addr, regnum, val);
	mutex_unlock(&bus->mdio_lock);

	return err;
}
EXPORT_SYMBOL(mdiobus_write);

> 
> Thanks,
> 
> John
> --
> John Williams, PhD, B.Eng, B.IT
> PetaLogix - Linux Solutions for a Reconfigurable World
> w: www.petalogix.com  p: +61-7-30090663  f: +61-7-30090663


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