Re: [PATCH net-next 4/7] net: phy: add paged phy register accessors

[Russell King - ARM Linux <linux@armlinux.org.uk>]

On Sun, Dec 31, 2017 at 09:10:39AM +0100, Andrew Lunn wrote:
> > +/**
> > + * phy_save_page() - take the bus lock and save the current page
> > + * @phydev: a pointer to a &struct phy_device
> > + *
> > + * Take the MDIO bus lock, and return the current page number. On error,
> > + * returns a negative errno. phy_restore_page() must be called after this
> > + * to release the lock even on failure.
> > + */
> > +int phy_save_page(struct phy_device *phydev)
> > +{
> > +	mutex_lock(&phydev->mdio.bus->mdio_lock);
> > +	return __phy_read_page(phydev);
> > +}
> > +EXPORT_SYMBOL_GPL(phy_save_page);
> > +
> > +/**
> > + * phy_select_page() - take the bus lock, save the current page, and set a page
> > + * @phydev: a pointer to a &struct phy_device
> > + * @page: desired page
> > + *
> > + * Take the MDIO bus lock to protect against concurrent access, save the
> > + * current PHY page, and set the current page.  On error, returns a
> > + * negative errno, otherwise returns the previous page number.
> > + * phy_restore_page() must be called after this to restore the page
> > + * number (if this call was successful) and release the lock.
> 
> Hi Russell
> 
> This comment seems wrong. It looks like you need to call
> phy_restore_page() on error as well. I think the text in () should be
> removed, and add the "even on failure" which the previous function
> states.

It's one of those slightly confusing bits of English, and I doubt
there's a way to express it better.

  phy_restore_page() must be called after this to [restore the page
  number (if this call was successful) and] release the lock.

I could use:

  phy_restore_page() must always be called to release the lock,
  and restore the page number if this call was successful.

but that can still be read in an ambiguous manner.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up