On 12/08/2017 08:44 AM, Russell King - ARM Linux wrote: > On Fri, Dec 08, 2017 at 05:17:14PM +0100, Andrew Lunn wrote: >> Hi Russell >> >>> There is an open question whether there should be generic helpers for >>> this. Generic helpers would mean: >>> >>> - Additional couple of function pointers in phy_driver to read/write the >>> paging register. This has the restriction that there must only be one >>> paging register. >> >> I must be missing something. I don't see why there is this >> restriction. Don't we just need >> >> int phy_get_page(phydev); >> int phy_set_page(phydev, page); > > The restriction occurs because a PHY may have several different > registers, and knowing which of the registers need touching becomes an > issue. We wouldn't want these accessors to needlessly access several > registers each and every time we requested an access to the page > register. > > There's also the issue of whether an "int" or whatever type we choose to > pass the "page" around is enough bits. I haven't surveyed all the PHY > drivers yet to know the answer to that.
I have not come across a PHY yet that required writing a page across two 16-bit quantities, in general, the page fits within less than 16-bit actually to fit within one MDIO write. That does not mean it cannot exist obviously, but having about 32-bit x pages of address space within a PHY sounds a bit extreme. -- Florian
