netdev - Re: [net-next PATCH v7 02/16] net: phy: Introduce fwnode_mdio_find

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Date:   Thu, 11 Mar 2021 22:28:42 +0530
From:   Calvin Johnson <calvin.johnson@....nxp.com>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Grant Likely <grant.likely@....com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Cristi Sovaiala <cristian.sovaiala@....com>,
        Florin Laurentiu Chiculita <florinlaurentiu.chiculita@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Pieter Jansen Van Vuuren <pieter.jansenvv@...boosystems.io>,
        Jon <jon@...id-run.com>, Randy Dunlap <rdunlap@...radead.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Diana Madalina Craciun <diana.craciun@....com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux.cj" <linux.cj@...il.com>, netdev <netdev@...r.kernel.org>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [net-next PATCH v7 02/16] net: phy: Introduce
 fwnode_mdio_find_device()

On Wed, Mar 10, 2021 at 10:50:57PM -0800, Saravana Kannan wrote:
> On Wed, Mar 10, 2021 at 10:21 PM Calvin Johnson
> <calvin.johnson@....nxp.com> wrote:
> >
> > Define fwnode_mdio_find_device() to get a pointer to the
> > mdio_device from fwnode passed to the function.
> >
> > Refactor of_mdio_find_device() to use fwnode_mdio_find_device().
> >
> > Signed-off-by: Calvin Johnson <calvin.johnson@....nxp.com>
> > ---
> >
> > Changes in v7:
> > - correct fwnode_mdio_find_device() description
> >
> > Changes in v6:
> > - fix warning for function parameter of fwnode_mdio_find_device()
> >
> > Changes in v5: None
> > Changes in v4: None
> > Changes in v3: None
> > Changes in v2: None
> >
> >  drivers/net/mdio/of_mdio.c   | 11 +----------
> >  drivers/net/phy/phy_device.c | 23 +++++++++++++++++++++++
> >  include/linux/phy.h          |  6 ++++++
> >  3 files changed, 30 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
> > index ea9d5855fb52..d5e0970b2561 100644
> > --- a/drivers/net/mdio/of_mdio.c
> > +++ b/drivers/net/mdio/of_mdio.c
> > @@ -347,16 +347,7 @@ EXPORT_SYMBOL(of_mdiobus_register);
> >   */
> >  struct mdio_device *of_mdio_find_device(struct device_node *np)
> >  {
> > -       struct device *d;
> > -
> > -       if (!np)
> > -               return NULL;
> > -
> > -       d = bus_find_device_by_of_node(&mdio_bus_type, np);
> > -       if (!d)
> > -               return NULL;
> > -
> > -       return to_mdio_device(d);
> > +       return fwnode_mdio_find_device(of_fwnode_handle(np));
> >  }
> >  EXPORT_SYMBOL(of_mdio_find_device);
> >
> > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> > index cc38e326405a..daabb17bba00 100644
> > --- a/drivers/net/phy/phy_device.c
> > +++ b/drivers/net/phy/phy_device.c
> > @@ -2819,6 +2819,29 @@ static bool phy_drv_supports_irq(struct phy_driver *phydrv)
> >         return phydrv->config_intr && phydrv->handle_interrupt;
> >  }
> >
> > +/**
> > + * fwnode_mdio_find_device - Given a fwnode, find the mdio_device
> > + * @fwnode: pointer to the mdio_device's fwnode
> > + *
> > + * If successful, returns a pointer to the mdio_device with the embedded
> > + * struct device refcount incremented by one, or NULL on failure.
> > + * The caller should call put_device() on the mdio_device after its use.
> > + */
> > +struct mdio_device *fwnode_mdio_find_device(struct fwnode_handle *fwnode)
> > +{
> > +       struct device *d;
> > +
> > +       if (!fwnode)
> > +               return NULL;
> > +
> > +       d = bus_find_device_by_fwnode(&mdio_bus_type, fwnode);
> 
> Sorry about the late review, but can you look into using
> get_dev_from_fwnode()? As long as you aren't registering two devices
> for the same fwnode, it's an O(1) operation instead of having to loop
> through a list of devices in a bus. You can check the returned
> device's bus type if you aren't sure about not registering two devices
> with the same fw_node and then fall back to this looping.

I think it is better to keep it simple and clear with
bus_find_device_by_fwnode() instead of the additional code that comes
with get_dev_from_fwnode() until it has clear advantage over the former.

regards
Calvin