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 13:27:27 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Florian Fainelli <f.fainelli@...il.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

Florian

On 5/22/20 11:11 AM, Florian Fainelli wrote:
>
> 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).

Ack

>
>> + */
>> +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?

Yes I guess it does.  I can add this to the k 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?

Yes and no it maybe better to start the for loop with i being 
initialized to 1 since the zeroth element is already validated above.

Dan