[PATCH 0/2] net: phy: Make phy_interface_is_sgmii|rgmii a switch statement

[PATCH 0/2] net: phy: Make phy_interface_is_sgmii|rgmii a switch statement

[Nishanth Menon]

Originally reported by Tom[1], turned out to be that recent commit
75d28899e3e9 ("net: phy: Synchronize PHY interface modes with Linux")
reordered the enum definitions which in turn broke the range checks.

we are left with two options:
a) check against explicit values to help reuse as much as possible and
let compiler optimize where applicable
or
b) be very explicit in phy drivers and drop these helpers.

I have chosen to go with (a) approach.

Tested on am64x, though the dp83867 is used elsewhere as well.

Nishanth Menon (2):
  net: phy: Make phy_interface_is_sgmii a switch statement
  net: phy: Make phy_interface_is_rgmii a switch statement

 include/phy.h | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

-- 
2.40.0

[PATCH 1/2] net: phy: Make phy_interface_is_sgmii a switch statement

[Nishanth Menon]

Recent commit 75d28899e3e9 ("net: phy: Synchronize PHY interface modes
with Linux") reordered the enum definitions. This caused the range of
enums that this api was checking to go bad.

While it is possible for the phy drivers to practically use the enum's
directly, drivers such as dp83867 use this helper to manage the
configuration of the phy correctly.

Reported-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
---
 include/phy.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/phy.h b/include/phy.h
index a837fed72352..1c4dc23bc5ba 100644
--- a/include/phy.h
+++ b/include/phy.h
@@ -373,8 +373,16 @@ static inline bool phy_interface_is_rgmii(struct phy_device *phydev)
  */
 static inline bool phy_interface_is_sgmii(struct phy_device *phydev)
 {
-	return phydev->interface >= PHY_INTERFACE_MODE_SGMII &&
-		phydev->interface <= PHY_INTERFACE_MODE_QSGMII;
+	switch (phydev->interface) {
+	case PHY_INTERFACE_MODE_SGMII:
+	case PHY_INTERFACE_MODE_QUSGMII:
+	case PHY_INTERFACE_MODE_USXGMII:
+	case PHY_INTERFACE_MODE_QSGMII:
+		return 1;
+	default:
+		fallthrough;
+	}
+	return 0;
 }
 
 bool phy_interface_is_ncsi(void);
-- 
2.40.0

[PATCH 2/2] net: phy: Make phy_interface_is_rgmii a switch statement

[Nishanth Menon]

Recent commit 75d28899e3e9 ("net: phy: Synchronize PHY interface modes
with Linux") reordered the enum definitions. This exposed a problem in
range checking functions to identify the interface type. Though this
specific api was'nt impacted (all the RGMII definitions remained within
range), this experience should be used to never to have to face this
kind of challenge again.

While it is possible for the phy drivers to practically use the enum's
directly, drivers such as dp83867, dp83869, marvell, micrel_ksz90x1 etc
use the same.

Reported-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
---
 include/phy.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/phy.h b/include/phy.h
index 1c4dc23bc5ba..812694cf4a81 100644
--- a/include/phy.h
+++ b/include/phy.h
@@ -361,8 +361,16 @@ int get_phy_id(struct mii_dev *bus, int addr, int devad, u32 *phy_id);
  */
 static inline bool phy_interface_is_rgmii(struct phy_device *phydev)
 {
-	return phydev->interface >= PHY_INTERFACE_MODE_RGMII &&
-		phydev->interface <= PHY_INTERFACE_MODE_RGMII_TXID;
+	switch (phydev->interface) {
+	case PHY_INTERFACE_MODE_RGMII:
+	case PHY_INTERFACE_MODE_RGMII_ID:
+	case PHY_INTERFACE_MODE_RGMII_RXID:
+	case PHY_INTERFACE_MODE_RGMII_TXID:
+		return 1;
+	default:
+		fallthrough;
+	}
+	return 0;
 }
 
 /**
-- 
2.40.0

Re: [PATCH 0/2] net: phy: Make phy_interface_is_sgmii|rgmii a switch statement

[Nishanth Menon]

On 13:07-20230413, Nishanth Menon wrote:
> Originally reported by Tom[1], turned out to be that recent commit
> 75d28899e3e9 ("net: phy: Synchronize PHY interface modes with Linux")
> reordered the enum definitions which in turn broke the range checks.
> 
> we are left with two options:
> a) check against explicit values to help reuse as much as possible and
> let compiler optimize where applicable
> or
> b) be very explicit in phy drivers and drop these helpers.
> 
> I have chosen to go with (a) approach.
> 
> Tested on am64x, though the dp83867 is used elsewhere as well.
> 
> Nishanth Menon (2):
>   net: phy: Make phy_interface_is_sgmii a switch statement
>   net: phy: Make phy_interface_is_rgmii a switch statement
> 
>  include/phy.h | 24 ++++++++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
> -- 
> 2.40.0
> 
Oops.. forgot to provide the link of the report:

[1] https://libera.irclog.whitequark.org/u-boot/2023-04-07#34130437;
-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D

Re: [PATCH 1/2] net: phy: Make phy_interface_is_sgmii a switch statement

[Marek Behún]

On Thu, Apr 13, 2023 at 01:07:12PM -0500, Nishanth Menon wrote:
> Recent commit 75d28899e3e9 ("net: phy: Synchronize PHY interface modes
> with Linux") reordered the enum definitions. This caused the range of
> enums that this api was checking to go bad.
> 
> While it is possible for the phy drivers to practically use the enum's
> directly, drivers such as dp83867 use this helper to manage the
> configuration of the phy correctly.
> 
> Reported-by: Tom Rini <trini@konsulko.com>
> Signed-off-by: Nishanth Menon <nm@ti.com>
> ---
>  include/phy.h | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/include/phy.h b/include/phy.h
> index a837fed72352..1c4dc23bc5ba 100644
> --- a/include/phy.h
> +++ b/include/phy.h
> @@ -373,8 +373,16 @@ static inline bool phy_interface_is_rgmii(struct phy_device *phydev)
>   */
>  static inline bool phy_interface_is_sgmii(struct phy_device *phydev)
>  {
> -	return phydev->interface >= PHY_INTERFACE_MODE_SGMII &&
> -		phydev->interface <= PHY_INTERFACE_MODE_QSGMII;
> +	switch (phydev->interface) {
> +	case PHY_INTERFACE_MODE_SGMII:
> +	case PHY_INTERFACE_MODE_QUSGMII:
> +	case PHY_INTERFACE_MODE_USXGMII:
> +	case PHY_INTERFACE_MODE_QSGMII:
> +		return 1;
> +	default:
> +		fallthrough;

Why not just put the return 0; statement here instead of fallthrough and
drop it from after the switch statement?

> +	}
> +	return 0;
>  }

Re: [PATCH 1/2] net: phy: Make phy_interface_is_sgmii a switch statement

[Nishanth Menon]

On 20:56-20230413, Marek Behún wrote:
> On Thu, Apr 13, 2023 at 01:07:12PM -0500, Nishanth Menon wrote:
> > Recent commit 75d28899e3e9 ("net: phy: Synchronize PHY interface modes
> > with Linux") reordered the enum definitions. This caused the range of
> > enums that this api was checking to go bad.
> > 
> > While it is possible for the phy drivers to practically use the enum's
> > directly, drivers such as dp83867 use this helper to manage the
> > configuration of the phy correctly.
> > 
> > Reported-by: Tom Rini <trini@konsulko.com>
> > Signed-off-by: Nishanth Menon <nm@ti.com>
> > ---
> >  include/phy.h | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/phy.h b/include/phy.h
> > index a837fed72352..1c4dc23bc5ba 100644
> > --- a/include/phy.h
> > +++ b/include/phy.h
> > @@ -373,8 +373,16 @@ static inline bool phy_interface_is_rgmii(struct phy_device *phydev)
> >   */
> >  static inline bool phy_interface_is_sgmii(struct phy_device *phydev)
> >  {
> > -	return phydev->interface >= PHY_INTERFACE_MODE_SGMII &&
> > -		phydev->interface <= PHY_INTERFACE_MODE_QSGMII;
> > +	switch (phydev->interface) {
> > +	case PHY_INTERFACE_MODE_SGMII:
> > +	case PHY_INTERFACE_MODE_QUSGMII:
> > +	case PHY_INTERFACE_MODE_USXGMII:
> > +	case PHY_INTERFACE_MODE_QSGMII:
> > +		return 1;
> > +	default:
> > +		fallthrough;
> 
> Why not just put the return 0; statement here instead of fallthrough and
> drop it from after the switch statement?

Just dropping the default also will work, though it does leave something
un-handled. handling the default on the other hand allows for additional
code (meh?) to be added in default.. But really what? I'd rather drop
the default and fall through to save on a couple of lines.. if that
is'nt creating confusion..

> > +	}
> > +	return 0;
> >  }

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D

Re: [PATCH 1/2] net: phy: Make phy_interface_is_sgmii a switch statement

[Marek Behún]

On Thu, Apr 13, 2023 at 02:02:34PM -0500, Nishanth Menon wrote:
> On 20:56-20230413, Marek Behún wrote:
> > On Thu, Apr 13, 2023 at 01:07:12PM -0500, Nishanth Menon wrote:
> > > Recent commit 75d28899e3e9 ("net: phy: Synchronize PHY interface modes
> > > with Linux") reordered the enum definitions. This caused the range of
> > > enums that this api was checking to go bad.
> > > 
> > > While it is possible for the phy drivers to practically use the enum's
> > > directly, drivers such as dp83867 use this helper to manage the
> > > configuration of the phy correctly.
> > > 
> > > Reported-by: Tom Rini <trini@konsulko.com>
> > > Signed-off-by: Nishanth Menon <nm@ti.com>
> > > ---
> > >  include/phy.h | 12 ++++++++++--
> > >  1 file changed, 10 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/include/phy.h b/include/phy.h
> > > index a837fed72352..1c4dc23bc5ba 100644
> > > --- a/include/phy.h
> > > +++ b/include/phy.h
> > > @@ -373,8 +373,16 @@ static inline bool phy_interface_is_rgmii(struct phy_device *phydev)
> > >   */
> > >  static inline bool phy_interface_is_sgmii(struct phy_device *phydev)
> > >  {
> > > -	return phydev->interface >= PHY_INTERFACE_MODE_SGMII &&
> > > -		phydev->interface <= PHY_INTERFACE_MODE_QSGMII;
> > > +	switch (phydev->interface) {
> > > +	case PHY_INTERFACE_MODE_SGMII:
> > > +	case PHY_INTERFACE_MODE_QUSGMII:
> > > +	case PHY_INTERFACE_MODE_USXGMII:
> > > +	case PHY_INTERFACE_MODE_QSGMII:
> > > +		return 1;
> > > +	default:
> > > +		fallthrough;
> > 
> > Why not just put the return 0; statement here instead of fallthrough and
> > drop it from after the switch statement?
> 
> Just dropping the default also will work, though it does leave something
> un-handled. handling the default on the other hand allows for additional
> code (meh?) to be added in default.. But really what? I'd rather drop
> the default and fall through to save on a couple of lines.. if that
> is'nt creating confusion..

You can't drop the default if you use a switch statement and not
enumerating all enumerator entries.

So you either have to use

	switch (x) {
	case A:
		return 1;
	case B:
		return 2;
	default:
		return 3;
	}

or

	switch (x) {
	case A:
		return 1;
	case B:
		return 2;
	default:
		break; /* or fallthourgh */
	}
	return 3;

The first one is shorter one line. It is also used in this way already.

IMO it makes more sense.

But keep in mind, this is just a nit-pick. I don't actually care that
much. I just think it makes more sense this way. If all possibilities
are handled by return statements inside the switch, you don't need to
have another return in top level of the function.

Look for example at Linux' include/linux/phy.h function phy_modes():
  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/phy.h?h=v6.3-rc6#n216

Marek

> 
> > > +	}
> > > +	return 0;
> > >  }
> 
> -- 
> Regards,
> Nishanth Menon
> Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D

Re: [PATCH 1/2] net: phy: Make phy_interface_is_sgmii a switch statement

[Nishanth Menon]

On 23:22-20230413, Marek Behún wrote:
> On Thu, Apr 13, 2023 at 02:02:34PM -0500, Nishanth Menon wrote:
> > On 20:56-20230413, Marek Behún wrote:
> > > On Thu, Apr 13, 2023 at 01:07:12PM -0500, Nishanth Menon wrote:
> > > > Recent commit 75d28899e3e9 ("net: phy: Synchronize PHY interface modes
> > > > with Linux") reordered the enum definitions. This caused the range of
> > > > enums that this api was checking to go bad.
> > > > 
> > > > While it is possible for the phy drivers to practically use the enum's
> > > > directly, drivers such as dp83867 use this helper to manage the
> > > > configuration of the phy correctly.
> > > > 
> > > > Reported-by: Tom Rini <trini@konsulko.com>
> > > > Signed-off-by: Nishanth Menon <nm@ti.com>
> > > > ---
> > > >  include/phy.h | 12 ++++++++++--
> > > >  1 file changed, 10 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/include/phy.h b/include/phy.h
> > > > index a837fed72352..1c4dc23bc5ba 100644
> > > > --- a/include/phy.h
> > > > +++ b/include/phy.h
> > > > @@ -373,8 +373,16 @@ static inline bool phy_interface_is_rgmii(struct phy_device *phydev)
> > > >   */
> > > >  static inline bool phy_interface_is_sgmii(struct phy_device *phydev)
> > > >  {
> > > > -	return phydev->interface >= PHY_INTERFACE_MODE_SGMII &&
> > > > -		phydev->interface <= PHY_INTERFACE_MODE_QSGMII;
> > > > +	switch (phydev->interface) {
> > > > +	case PHY_INTERFACE_MODE_SGMII:
> > > > +	case PHY_INTERFACE_MODE_QUSGMII:
> > > > +	case PHY_INTERFACE_MODE_USXGMII:
> > > > +	case PHY_INTERFACE_MODE_QSGMII:
> > > > +		return 1;
> > > > +	default:
> > > > +		fallthrough;
> > > 
> > > Why not just put the return 0; statement here instead of fallthrough and
> > > drop it from after the switch statement?
> > 
> > Just dropping the default also will work, though it does leave something
> > un-handled. handling the default on the other hand allows for additional
> > code (meh?) to be added in default.. But really what? I'd rather drop
> > the default and fall through to save on a couple of lines.. if that
> > is'nt creating confusion..
> 
> You can't drop the default if you use a switch statement and not
> enumerating all enumerator entries.
> 
> So you either have to use
> 
> 	switch (x) {
> 	case A:
> 		return 1;
> 	case B:
> 		return 2;
> 	default:
> 		return 3;
> 	}
> 
> or
> 
> 	switch (x) {
> 	case A:
> 		return 1;
> 	case B:
> 		return 2;
> 	default:
> 		break; /* or fallthourgh */
> 	}
> 	return 3;
> 
> The first one is shorter one line. It is also used in this way already.
> 
> IMO it makes more sense.
> 
> But keep in mind, this is just a nit-pick. I don't actually care that
> much. I just think it makes more sense this way. If all possibilities
> are handled by return statements inside the switch, you don't need to
> have another return in top level of the function.

Sigh, remnants of a few years of misra misery :( - yep, dropping..

new rev incoming..

> 
> Look for example at Linux' include/linux/phy.h function phy_modes():
>   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/phy.h?h=v6.3-rc6#n216
> 

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D

Re: [PATCH 2/2] net: phy: Make phy_interface_is_rgmii a switch statement

[Ramon Fried]

On Thu, Apr 13, 2023 at 9:07 PM Nishanth Menon <nm@ti.com> wrote:
>
> Recent commit 75d28899e3e9 ("net: phy: Synchronize PHY interface modes
> with Linux") reordered the enum definitions. This exposed a problem in
> range checking functions to identify the interface type. Though this
> specific api was'nt impacted (all the RGMII definitions remained within
> range), this experience should be used to never to have to face this
> kind of challenge again.
>
> While it is possible for the phy drivers to practically use the enum's
> directly, drivers such as dp83867, dp83869, marvell, micrel_ksz90x1 etc
> use the same.
>
> Reported-by: Tom Rini <trini@konsulko.com>
> Signed-off-by: Nishanth Menon <nm@ti.com>
> ---
>  include/phy.h | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/include/phy.h b/include/phy.h
> index 1c4dc23bc5ba..812694cf4a81 100644
> --- a/include/phy.h
> +++ b/include/phy.h
> @@ -361,8 +361,16 @@ int get_phy_id(struct mii_dev *bus, int addr, int devad, u32 *phy_id);
>   */
>  static inline bool phy_interface_is_rgmii(struct phy_device *phydev)
>  {
> -       return phydev->interface >= PHY_INTERFACE_MODE_RGMII &&
> -               phydev->interface <= PHY_INTERFACE_MODE_RGMII_TXID;
> +       switch (phydev->interface) {
> +       case PHY_INTERFACE_MODE_RGMII:
> +       case PHY_INTERFACE_MODE_RGMII_ID:
> +       case PHY_INTERFACE_MODE_RGMII_RXID:
> +       case PHY_INTERFACE_MODE_RGMII_TXID:
> +               return 1;
> +       default:
> +               fallthrough;
> +       }
> +       return 0;
>  }
>
>  /**
> --
> 2.40.0
>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>