RFC: stmmac RSS support

["Russell King (Oracle)" <linux@armlinux.org.uk>]

Hi,

While looking at the possibilities of minimising the memory that
struct plat_stmmacenet_data consumes (880 bytes presently on
aarch64), I came across the RSS feature in stmmac.

In commit 76067459c686 ("net: stmmac: Implement RSS and enable it in
XGMAC core"), support was added for RSS to the core stmmac driver for
the dwxgmac2 core. I can only find socfpga and tegra as the two
platform glues that use the dwxgmac2 core.

RSS support is only enabled when both the core supports it, and the
platform glue sets priv->plat->rss_en.

However, the stmmac-related results of grepping for this member do not
show any platform glues which set this flag:

$ git grep '\<rss_en\>'
Documentation/networking/device_drivers/ethernet/stmicro/stmmac.rst:        int rss_en;
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:      if (!priv->dma_cap.rssen || !priv->plat->rss_en) {
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:      if (priv->dma_cap.rssen && priv->plat->rss_en)

So, as no one has decided to enable this feature during the intervening
six years, is there any benefit to having this code in the mainline
kernel, or should this feature be dropped?

If a user appears, the code will remain in git history and could be
restored.

Thoughts?

-- 
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