net: mvneta: Use min macro

[PATCH net-next v3] net: mvneta: Use min macro

Posted by Yan Zhen 1 year, 5 months ago

Using the real macro is usually more intuitive and readable,
When the original file is guaranteed to contain the minmax.h header file
and compile correctly.

Signed-off-by: Yan Zhen <yanzhen@vivo.com>
---

Changes in v3:
- Rewrite the subject.

 drivers/net/ethernet/marvell/mvneta.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index d72b2d5f96db..08d277165f40 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -4750,8 +4750,7 @@ mvneta_ethtool_set_ringparam(struct net_device *dev,
 
 	if ((ring->rx_pending == 0) || (ring->tx_pending == 0))
 		return -EINVAL;
-	pp->rx_ring_size = ring->rx_pending < MVNETA_MAX_RXD ?
-		ring->rx_pending : MVNETA_MAX_RXD;
+	pp->rx_ring_size = umin(ring->rx_pending, MVNETA_MAX_RXD);
 
 	pp->tx_ring_size = clamp_t(u16, ring->tx_pending,
 				   MVNETA_MAX_SKB_DESCS * 2, MVNETA_MAX_TXD);
-- 
2.34.1

RE: [PATCH net-next v3] net: mvneta: Use min macro

Posted by David Laight 1 year, 5 months ago

From: Yan Zhen
> Sent: 30 August 2024 02:04
> To: marcin.s.wojtas@gmail.com; davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> 
> Using the real macro is usually more intuitive and readable,
> When the original file is guaranteed to contain the minmax.h header file
> and compile correctly.
> 
> Signed-off-by: Yan Zhen <yanzhen@vivo.com>
> ---
> 
> Changes in v3:
> - Rewrite the subject.
> 
>  drivers/net/ethernet/marvell/mvneta.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index d72b2d5f96db..08d277165f40 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -4750,8 +4750,7 @@ mvneta_ethtool_set_ringparam(struct net_device *dev,
> 
>  	if ((ring->rx_pending == 0) || (ring->tx_pending == 0))
>  		return -EINVAL;
> -	pp->rx_ring_size = ring->rx_pending < MVNETA_MAX_RXD ?
> -		ring->rx_pending : MVNETA_MAX_RXD;
> +	pp->rx_ring_size = umin(ring->rx_pending, MVNETA_MAX_RXD);

Why did you use umin() instead of min() ?

> 
>  	pp->tx_ring_size = clamp_t(u16, ring->tx_pending,
>  				   MVNETA_MAX_SKB_DESCS * 2, MVNETA_MAX_TXD);

Hmmm how about a patch to fix the bug in that line?
A typical example of the complete misuse of the '_t' variants.
The fact that the LHS is u16 doesn't mean that it is anyway
correct to cast the RHS value to u16.
In this case if someone tries to set the ring size to 64k they'll
get the minimum supported size and not the maximum.

	David

> --
> 2.34.1
> 

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH net-next v3] net: mvneta: Use min macro

Posted by Simon Horman 1 year, 5 months ago

On Sun, Sep 01, 2024 at 10:52:38AM +0000, David Laight wrote:
> From: Yan Zhen
> > Sent: 30 August 2024 02:04
> > To: marcin.s.wojtas@gmail.com; davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> > 
> > Using the real macro is usually more intuitive and readable,
> > When the original file is guaranteed to contain the minmax.h header file
> > and compile correctly.
> > 
> > Signed-off-by: Yan Zhen <yanzhen@vivo.com>
> > ---
> > 
> > Changes in v3:
> > - Rewrite the subject.
> > 
> >  drivers/net/ethernet/marvell/mvneta.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> > index d72b2d5f96db..08d277165f40 100644
> > --- a/drivers/net/ethernet/marvell/mvneta.c
> > +++ b/drivers/net/ethernet/marvell/mvneta.c
> > @@ -4750,8 +4750,7 @@ mvneta_ethtool_set_ringparam(struct net_device *dev,
> > 
> >  	if ((ring->rx_pending == 0) || (ring->tx_pending == 0))
> >  		return -EINVAL;
> > -	pp->rx_ring_size = ring->rx_pending < MVNETA_MAX_RXD ?
> > -		ring->rx_pending : MVNETA_MAX_RXD;
> > +	pp->rx_ring_size = umin(ring->rx_pending, MVNETA_MAX_RXD);
> 
> Why did you use umin() instead of min() ?

Possibly because I mistakenly advised it is appropriate, sorry about that.
Given your explanation elsewhere [1], I now agree min() is appropriate.

[1] https://lore.kernel.org/netdev/20240901171150.GA23170@kernel.org/T/#mebc52fc11de13eff8a610e3a63c5d1026d527492

> >  	pp->tx_ring_size = clamp_t(u16, ring->tx_pending,
> >  				   MVNETA_MAX_SKB_DESCS * 2, MVNETA_MAX_TXD);
> 
> Hmmm how about a patch to fix the bug in that line?
> A typical example of the complete misuse of the '_t' variants.
> The fact that the LHS is u16 doesn't mean that it is anyway
> correct to cast the RHS value to u16.
> In this case if someone tries to set the ring size to 64k they'll

Re: [PATCH net-next v3] net: mvneta: Use min macro

Posted by Simon Horman 1 year, 5 months ago

On Fri, Aug 30, 2024 at 09:04:23AM +0800, Yan Zhen wrote:
> Using the real macro is usually more intuitive and readable,
> When the original file is guaranteed to contain the minmax.h header file
> and compile correctly.
> 
> Signed-off-by: Yan Zhen <yanzhen@vivo.com>
> ---
> 
> Changes in v3:
> - Rewrite the subject.

Thanks for the update.

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net-next v3] net: mvneta: Use min macro

Posted by Marcin Wojtas 1 year, 5 months ago

pt., 30 sie 2024 o 17:45 Simon Horman <horms@kernel.org> napisał(a):
>
> On Fri, Aug 30, 2024 at 09:04:23AM +0800, Yan Zhen wrote:
> > Using the real macro is usually more intuitive and readable,
> > When the original file is guaranteed to contain the minmax.h header file
> > and compile correctly.
> >
> > Signed-off-by: Yan Zhen <yanzhen@vivo.com>
> > ---
> >
> > Changes in v3:
> > - Rewrite the subject.
>
> Thanks for the update.
>
> Reviewed-by: Simon Horman <horms@kernel.org>
>

Reviewed-by: Marcin Wojtas <marcin.s.wojtas@gmail.com>

Thanks!