linux-kernel - Re: [PATCH v1 net-next 1/1] net: ethernet: ocelot: remove the need for num

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Message-ID: <20220430151530.zaf7hyagln5jqjyi@skbuf>
Date:   Sat, 30 Apr 2022 15:15:31 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Colin Foster <colin.foster@...advantage.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        aolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Manoil <claudiu.manoil@....com>
Subject: Re: [PATCH v1 net-next 1/1] net: ethernet: ocelot: remove the need
 for num_stats initializer

On Fri, Apr 29, 2022 at 02:30:36PM -0700, Colin Foster wrote:
> There is a desire to share the oclot_stats_layout struct outside of the
> current vsc7514 driver. In order to do so, the length of the array needs to
> be known at compile time, and defined in the struct ocelot and struct
> felix_info.
> 
> Since the array is defined in a .c file and would be declared in the header
> file via:
> extern struct ocelot_stat_layout[];
> the size of the array will not be known at compile time to outside modules.
> 
> To fix this, remove the need for defining the number of stats at compile
> time and allow this number to be determined at initialization.
> 
> Signed-off-by: Colin Foster <colin.foster@...advantage.com>
> ---
> diff --git a/include/soc/mscc/ocelot.h b/include/soc/mscc/ocelot.h
> index 9b4e6c78d0f4..5c4f57cfa785 100644
> --- a/include/soc/mscc/ocelot.h
> +++ b/include/soc/mscc/ocelot.h
> @@ -105,6 +105,13 @@
>  #define REG_RESERVED_ADDR		0xffffffff
>  #define REG_RESERVED(reg)		REG(reg, REG_RESERVED_ADDR)
>  
> +#define OCELOT_STAT_FLAG_END		BIT(0)
> +
> +#define for_each_stat(ocelot, stat)				\
> +	for ((stat) = ocelot->stats_layout;			\
> +	     !((stat)->flags & OCELOT_STAT_FLAG_END);		\
> +	     (stat)++)
> +
>  enum ocelot_target {
>  	ANA = 1,
>  	QS,
> @@ -535,9 +542,12 @@ enum ocelot_ptp_pins {
>  
>  struct ocelot_stat_layout {
>  	u32 offset;
> +	u32 flags;

Was it really necessary to add an extra u32 to struct ocelot_stat_layout?
Couldn't you check for the end of stats by looking at stat->name[0] and
comparing against the null terminator, for an empty string?

>  	char name[ETH_GSTRING_LEN];
>  };
>  
> +#define OCELOT_STAT_END { .flags = OCELOT_STAT_FLAG_END }
> +
>  struct ocelot_stats_region {
>  	struct list_head node;
>  	u32 offset;
> -- 
> 2.25.1
>