Re: [PATCH net 1/2] net: stmmac: Limit FIFO size by hardware feature value

[Kunihiko Hayashi <hayashi.kunihiko@socionext.com>]

Hi Andrew,

On 2025/01/17 5:16, Andrew Lunn wrote:
> On Thu, Jan 16, 2025 at 11:08:52AM +0900, Kunihiko Hayashi wrote:
>> Tx/Rx FIFO size is specified by the parameter "{tx,rx}-fifo-depth" from
>> the platform layer.
>>
>> However, these values are constrained by upper limits determined by the
>> capabilities of each hardware feature. There is a risk that the upper
>> bits will be truncated due to the calculation, so it's appropriate to
>> limit them to the upper limit values.
> 
> Are these values hard coded in the platform layer? Or can they come
> from userspace?

My explanation is insufficient and misleading.
"From the platform layer" means the common layer of stmmac described in
"stmmac_platform.c".

> If they are hard coded, we should also fix them. So maybe add a
> netdev_warn(), and encourage the platform maintainers to fix their
> platform. If they are coming from userspace, we should consider
> failing the ethtool call with an -EINVAL, and maybe an extack with the
> valid range?

These values are derived from the devicetree and stored in the stmmac
private structure. They are hardware-specific values, so I think this
fix is sufficient.

Thank you,

---
Best Regards
Kunihiko Hayashi