[PATCH 7/7] commands: Add mdio_read and mdio_write

[Sascha Hauer]

On Tue, Jan 26, 2016 at 06:09:00PM -0800, Andrey Smirnov wrote:
> On Tue, Jan 26, 2016 at 1:55 PM, Sascha Hauer <s.hauer at pengutronix.de> wrote:
> > On Mon, Jan 25, 2016 at 09:55:58PM -0800, Andrey Smirnov wrote:
> >> Add commands for low-level access to MDIO bus.
> >
> > Do we really need this? We can already read/write phy registers using
> > /dev/phyx which imo is quite convenient since it can be accessed with
> > regular md/mw commands.
> >
> > This of course is currently limited to the phys that are actually
> > registered, you can't just bang on MDIO addresses on which no phys are
> > registered. Maybe we could register all phys on a MDIO bus instead of
> > only the used ones?
> 
> Just to explain the purpose of this patch -- there are number of
> reasons we might want to be able to access "unregistered" PHYs:
> 
> - Not all MDIO attached devices would have PHYSID1,2 registers
> available which might cause mdiobus_scan() to not detect those PHYs
> 
> - MDIO bus troubleshooting
> 
> As for registering all PHYs on a bus, correct me if I am wrong but
> that would result in 32*N number of entries in /dev, where N is number
> of MDIO buses in the system. The device I am working with right now
> has 3 MDIO buses which would mean that I'd end up with 96 additional
> entries in /dev, which might be a little bit overwhelming from UI
> point of view. The other UI problem with that approach is that
> /dev/phy's are numbered linearly so in order to figure out how to
> access device on bus N at address M, user would have to perform N*32 +
> M in their head.

We could register the phys with name like:

	"mdio%d-phy%02x", dev->bus->dev.id, mdev->addr

That would make it clear which phy belongs to which bus.

Sascha

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