linux-kernel - Re: [PATCH 5/9] net: ethernet: ti: cpts: add return value to tx and rx timestamp funcitons

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Date:   Wed, 14 Sep 2016 16:00:15 +0200
From:   Richard Cochran <richardcochran@...il.com>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Mugunthan V N <mugunthanvnm@...com>,
        Sekhar Nori <nsekhar@...com>, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, WingMan Kwok <w-kwok2@...com>
Subject: Re: [PATCH 5/9] net: ethernet: ti: cpts: add return value to tx and
 rx timestamp funcitons

On Wed, Sep 14, 2016 at 04:02:27PM +0300, Grygorii Strashko wrote:
> From: WingMan Kwok <w-kwok2@...com>
> 
> Added return values in tx and rx timestamp funcitons facilitate the
> possibililies of timestamping by CPSW modules other than CPTS, such as
> packet accelerator on Keystone 2 devices.

I'm sorry, this is totally bogus.
 
> Signed-off-by: WingMan Kwok <w-kwok2@...com>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> ---
>  drivers/net/ethernet/ti/cpts.c | 16 ++++++++++------
>  drivers/net/ethernet/ti/cpts.h | 11 +++++++----
>  2 files changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ti/cpts.c b/drivers/net/ethernet/ti/cpts.c
> index 1ee64c6..970d4e2 100644
> --- a/drivers/net/ethernet/ti/cpts.c
> +++ b/drivers/net/ethernet/ti/cpts.c
> @@ -302,34 +302,38 @@ static u64 cpts_find_ts(struct cpts *cpts, struct sk_buff *skb, int ev_type)
>  	return ns;
>  }
>  
> -void cpts_rx_timestamp(struct cpts *cpts, struct sk_buff *skb)
> +int cpts_rx_timestamp(struct cpts *cpts, struct sk_buff *skb)
>  {
>  	u64 ns;
>  	struct skb_shared_hwtstamps *ssh;
>  
>  	if (!cpts || !cpts->rx_enable)
> -		return;
> +		return -EPERM;

EPERM?  Come on.

>  	ns = cpts_find_ts(cpts, skb, CPTS_EV_RX);
>  	if (!ns)
> -		return;
> +		return -ENOENT;
>  	ssh = skb_hwtstamps(skb);
>  	memset(ssh, 0, sizeof(*ssh));
>  	ssh->hwtstamp = ns_to_ktime(ns);
> +
> +	return 0;
>  }
>  
> -void cpts_tx_timestamp(struct cpts *cpts, struct sk_buff *skb)
> +int cpts_tx_timestamp(struct cpts *cpts, struct sk_buff *skb)
>  {
>  	u64 ns;
>  	struct skb_shared_hwtstamps ssh;
>  
>  	if (!cpts || !(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS))
> -		return;
> +		return -EPERM;
>  	ns = cpts_find_ts(cpts, skb, CPTS_EV_TX);
>  	if (!ns)
> -		return;
> +		return -ENOENT;
>  	memset(&ssh, 0, sizeof(ssh));
>  	ssh.hwtstamp = ns_to_ktime(ns);
>  	skb_tstamp_tx(skb, &ssh);
> +
> +	return 0;
>  }
>  
>  int cpts_register(struct cpts *cpts)
> diff --git a/drivers/net/ethernet/ti/cpts.h b/drivers/net/ethernet/ti/cpts.h
> index a865193..47026ec 100644
> --- a/drivers/net/ethernet/ti/cpts.h
> +++ b/drivers/net/ethernet/ti/cpts.h
> @@ -129,8 +129,8 @@ struct cpts {
>  	struct cpts_event pool_data[CPTS_MAX_EVENTS];
>  };
>  
> -void cpts_rx_timestamp(struct cpts *cpts, struct sk_buff *skb);
> -void cpts_tx_timestamp(struct cpts *cpts, struct sk_buff *skb);
> +int cpts_rx_timestamp(struct cpts *cpts, struct sk_buff *skb);
> +int cpts_tx_timestamp(struct cpts *cpts, struct sk_buff *skb);
>  int cpts_register(struct cpts *cpts);
>  void cpts_unregister(struct cpts *cpts);
>  struct cpts *cpts_create(struct device *dev, void __iomem *regs,
> @@ -162,11 +162,14 @@ static inline bool cpts_is_tx_enabled(struct cpts *cpts)
>  #else
>  struct cpts;
>  
> -static inline void cpts_rx_timestamp(struct cpts *cpts, struct sk_buff *skb)
> +static inline int cpts_rx_timestamp(struct cpts *cpts, struct sk_buff *skb)
>  {
> +	return -EOPNOTSUPP;

You are planning to check in the hot path if a compile time feature is
enabled?

Brilliant stuff.

>  }
> -static inline void cpts_tx_timestamp(struct cpts *cpts, struct sk_buff *skb)
> +
> +static inline int cpts_tx_timestamp(struct cpts *cpts, struct sk_buff *skb)
>  {
> +	return -EOPNOTSUPP;
>  }
>  
>  static inline
> -- 
> 2.9.3
> 

Thanks,
Richard