Re: [PATCH net 1/2] net: stmmac: est: Fix GCL bounds checks

["G Thomas, Rohan" <rohan.g.thomas@altera.com>]

Hi Jakub,

Thanks for reviewing the patch.

On 9/12/2025 5:31 AM, Jakub Kicinski wrote:
> On Thu, 11 Sep 2025 18:12:16 +0530 G Thomas, Rohan wrote:
>> On 9/11/2025 4:54 PM, Russell King (Oracle) wrote:
>>> On Thu, Sep 11, 2025 at 04:22:59PM +0800, Rohan G Thomas via B4 Relay wrote:
>>>> @@ -1012,7 +1012,7 @@ static int tc_taprio_configure(struct stmmac_priv *priv,
>>>>    		s64 delta_ns = qopt->entries[i].interval;
>>>>    		u32 gates = qopt->entries[i].gate_mask;
>>>>    
>>>> -		if (delta_ns > GENMASK(wid, 0))
>>>> +		if (delta_ns >= BIT(wid))
>>>
>>> While I agree this makes it look better, you don't change the version
>>> below, which makes the code inconsistent. I also don't see anything
>>> wrong with the original comparison.
>>
>> Just to clarify the intent behind this change:
>> For example, if wid = 3, then GENMASK(3, 0) = 0b1111 = 15. But the
>> maximum supported gate interval in this case is actually 7, since only 3
>> bits are available to represent the value. So in the patch, the
>> condition delta_ns >= BIT(wid) effectively checks if delta_ns is 8 or
>> more, which correctly returns an error for values that exceed the 3-bit
>> limit.
> 
> Comparison to BIT() looks rather odd, I think it's better to correct
> the GENMASK() bound?

Sure I'll update the condition to use GENMASK(wid - 1, 0) in the next
version. That should make the logic consistent with the checks below.

Best Regards,
Rohan