Re: [PATCH net-next v6 1/9] net: dsa: microchip: Add support for KSZ8463 global irq

[Bastien Curutchet <bastien.curutchet@bootlin.com>]

Hi Vladimir,

On 3/5/26 10:56 AM, Vladimir Oltean wrote:
> On Wed, Mar 04, 2026 at 11:18:52AM +0100, Bastien Curutchet (Schneider Electric) wrote:
>> @@ -2890,14 +2899,18 @@ static irqreturn_t ksz_irq_thread_fn(int irq, void *dev_id)
>>   	unsigned int nhandled = 0;
>>   	struct ksz_device *dev;
>>   	unsigned int sub_irq;
>> -	u8 data;
>> +	u16 data;
>>   	int ret;
>>   	u8 n;
>>   
>>   	dev = kirq->dev;
>>   
>> -	/* Read interrupt status register */
>> -	ret = ksz_read8(dev, kirq->reg_status, &data);
>> +	/*
>> +	 * Most of the KSZ switches have a 8-bits long interrupt status
>> +	 * register, but the KSZ8463 has a 16-bits long one. The overread here
>> +	 * is safe because we only iterate over kirq->nirqs in the below loop.
> 
> FWIW, this isn't the only thing making an overread "safe".
> If the adjacent register also has "clear on read" semantics, that's not
> good.
> 
> I can't tell whether that's the case here, though. There are just too
> many hardware variations to check for. I just wanted to point out that
> the reasoning is incomplete.
> 
You're right, I hadn't thought about the 'clear on read' case.

I'll use ksz_read16() only for the KSZ8463 to be 100% sure it won't 
break anything for other switches.


Best regards,
Bastien