net: pcs: add helpers to xpcs and lynx to manage mdiodev
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Cover letter [PATCH net-next 0/6] net: pcs: add helpers to xpcs and lynx to manage mdiodev
Hi,
This morning, we have had two instances where the destruction of the MDIO device associated with XPCS and Lynx has been wrong. Rather than allowing this pattern of errors to continue, let's make it easier for driver authors to get this right by adding a helper.
The changes are essentially:
1. Add two new mdio device helpers to manage the underlying struct device reference count. Note that the existing mdio_device_free() doesn't actually free anything, it merely puts the reference count.
2. Make the existing _create() and _destroy() PCS driver methods increment and decrement this refcount using these helpers. This results in no overall change, although drivers may hang on to the mdio device for a few cycles longer.
3. Add _create_mdiodev() which creates the mdio device before calling the existing _create() method. Once the _create() method has returned, we put the reference count on the mdio device.
If _create() was successful, then the reference count taken there will "hold" the mdio device for the lifetime of the PCS (in other words, until _destroy() is called.) However, if _create() failed, then dropping the refcount at this point will free the mdio device.
This is the exact behaviour we desire.
4. Convert users that create a mdio device and then call the PCS's _create() method over to the new _create_mdiodev() method, and simplify the cleanup.
We also have DPAA2 and fmem_memac that look up their PCS rather than creating it. These could also drop their reference count on the MDIO device immediately after calling lynx_pcs_create(), which would then mean we wouldn't need lynx_get_mdio_device() and the associated complexity to put the device in dpaa2_pcs_destroy() and pcs_put(). Note that DPAA2 bypasses the mdio device's abstractions by calling put_device() directly.
drivers/net/dsa/ocelot/felix_vsc9959.c | 20 +++------------ drivers/net/dsa/ocelot/seville_vsc9953.c | 20 +++------------ drivers/net/ethernet/freescale/enetc/enetc_pf.c | 22 +++------------- drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c | 15 +++-------- drivers/net/pcs/pcs-lynx.c | 31 +++++++++++++++++++++++ drivers/net/pcs/pcs-xpcs.c | 28 ++++++++++++++++++++ include/linux/mdio.h | 10 ++++++++ include/linux/pcs-lynx.h | 1 + include/linux/pcs/pcs-xpcs.h | 2 ++ 9 files changed, 87 insertions(+), 62 deletions(-)
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