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Message-ID: <ZN4cM+EvXUtTqNwH@shell.armlinux.org.uk> Date: Thu, 17 Aug 2023 14:10:11 +0100 From: "Russell King (Oracle)" <linux@...linux.org.uk> To: Ruan Jinjie <ruanjinjie@...wei.com> Cc: rafal@...ecki.pl, bcm-kernel-feedback-list@...adcom.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, opendmb@...il.com, florian.fainelli@...adcom.com, bryan.whitehead@...rochip.com, andrew@...n.ch, hkallweit1@...il.com, mdf@...nel.org, pgynther@...gle.com, Pavithra.Sathyanarayanan@...rochip.com, netdev@...r.kernel.org Subject: Re: [PATCH net-next v2 1/4] net: phy: fixed_phy: Fix return value check for fixed_phy_get_gpiod On Thu, Aug 17, 2023 at 08:16:28PM +0800, Ruan Jinjie wrote: > Since fixed_phy_get_gpiod() return NULL instead of ERR_PTR(), > if it fails, the IS_ERR() can never return the error. So check NULL > and return ERR_PTR(-EINVAL) if fails. No, this is totally and utterly wrong, and this patch introduces a new bug. The original code is _correct_. > Fixes: 71bd106d2567 ("net: fixed-phy: Add fixed_phy_register_with_gpiod() API") > Signed-off-by: Ruan Jinjie <ruanjinjie@...wei.com> > --- > drivers/net/phy/fixed_phy.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/phy/fixed_phy.c b/drivers/net/phy/fixed_phy.c > index aef739c20ac4..4e7406455b6e 100644 > --- a/drivers/net/phy/fixed_phy.c > +++ b/drivers/net/phy/fixed_phy.c > @@ -239,8 +239,8 @@ static struct phy_device *__fixed_phy_register(unsigned int irq, > /* Check if we have a GPIO associated with this fixed phy */ > if (!gpiod) { > gpiod = fixed_phy_get_gpiod(np); > - if (IS_ERR(gpiod)) > - return ERR_CAST(gpiod); > + if (!gpiod) > + return ERR_PTR(-EINVAL); Let's look at fixed_phy_get_gpiod(): gpiod = fwnode_gpiod_get_index(of_fwnode_handle(fixed_link_node), "link", 0, GPIOD_IN, "mdio"); if (IS_ERR(gpiod) && PTR_ERR(gpiod) != -EPROBE_DEFER) { ... gpiod = NULL; } ... return gpiod; If fwnode_gpiod_get_index() returns -EPROBE_DEFER, _then_ we return an error pointer. So it _does_ return an error pointer. It also returns NULL when there is no device node passed to it, or if there is no fixed-link specifier, or there is some other error from fwnode_gpiod_get_index(). Otherwise, it returns a valid pointer to a gpio descriptor. The gpio is optional. The device node is optional. When fixed_phy_get_gpiod() returns NULL, it is _not_ an error, it means that we don't have a GPIO. Just because something returns NULL does _not_ mean it's an error - please get out of that thinking, because if you don't your patches will introduce lots of new bugs. Only when fwnode_gpiod_get_index() wants to defer probe do we return an error. So, sorry but NAK to this patch, it is incorrect. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
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