linux-kernel - Re: [PATCH net-next v2 2/4] net: phy: Add a helper to return the index for of the internal delay

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Date:   Fri, 22 May 2020 09:11:09 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Dan Murphy <dmurphy@...com>, andrew@...n.ch, hkallweit1@...il.com,
        davem@...emloft.net, robh@...nel.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/4] net: phy: Add a helper to return the
 index for of the internal delay



On 5/22/2020 5:25 AM, Dan Murphy wrote:
> Add a helper function that will return the index in the array for the
> passed in internal delay value.  The helper requires the array, size and
> delay value.
> 
> The helper will then return the index for the exact match or return the
> index for the index to the closest smaller value.
> 
> Signed-off-by: Dan Murphy <dmurphy@...com>
> ---
>  drivers/net/phy/phy_device.c | 45 ++++++++++++++++++++++++++++++++++++
>  include/linux/phy.h          |  2 ++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 7481135d27ab..40f53b379d2b 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -2661,6 +2661,51 @@ void phy_get_pause(struct phy_device *phydev, bool *tx_pause, bool *rx_pause)
>  }
>  EXPORT_SYMBOL(phy_get_pause);
>  
> +/**
> + * phy_get_delay_index - returns the index of the internal delay
> + * @phydev: phy_device struct
> + * @delay_values: array of delays the PHY supports
> + * @size: the size of the delay array
> + * @delay: the delay to be looked up
> + *
> + * Returns the index within the array of internal delay passed in.

Can we consider using s32 for storage that way the various
of_read_property_read_u32() are a natural fit (int works too, but I
would prefer being explicit).

> + */
> +int phy_get_delay_index(struct phy_device *phydev, int *delay_values, int size,
> +			int delay)
> +{
> +	int i;
> +
> +	if (size <= 0)
> +		return -EINVAL;
> +
> +	if (delay <= delay_values[0])
> +		return 0;
> +
> +	if (delay > delay_values[size - 1])
> +		return size - 1;

Does not that assume that the delays are sorted by ascending order, if
so, can you make it clear in the kernel doc?

> +
> +	for (i = 0; i < size; i++) {
> +		if (delay == delay_values[i])
> +			return i;
> +
> +		/* Find an approximate index by looking up the table */
> +		if (delay > delay_values[i - 1] &&

&& i > 0 so you do not accidentally under-run the array?

> +		    delay < delay_values[i]) {
> +			if (delay - delay_values[i - 1] < delay_values[i] - delay)
> +				return i - 1;
> +			else
> +				return i;
> +		}
> +
> +	}
> +
> +	phydev_err(phydev, "error finding internal delay index for %d\n",
> +		   delay);
> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL(phy_get_delay_index);
> +
>  static bool phy_drv_supports_irq(struct phy_driver *phydrv)
>  {
>  	return phydrv->config_intr && phydrv->ack_interrupt;
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index 2bcdf19ed3b4..73552612c189 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -1408,6 +1408,8 @@ void phy_set_asym_pause(struct phy_device *phydev, bool rx, bool tx);
>  bool phy_validate_pause(struct phy_device *phydev,
>  			struct ethtool_pauseparam *pp);
>  void phy_get_pause(struct phy_device *phydev, bool *tx_pause, bool *rx_pause);
> +int phy_get_delay_index(struct phy_device *phydev, int *delay_values,
> +			int size, int delay);
>  void phy_resolve_pause(unsigned long *local_adv, unsigned long *partner_adv,
>  		       bool *tx_pause, bool *rx_pause);
>  
> 

-- 
Florian