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Documentation: networking: phy.txt: Update text for indirect MMD access

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Update the PHY library documentation to describe how a specific PHY
driver can use the PAL MMD register access routines or override those
routines with it's own in the event the PHY does not support the IEEE
standard for reading and writing MMD phy registers.

Signed-off-by: Vince Bridgers <vbridgers2013@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vince Bridgers 2014-07-29 15:19:59 -05:00 committed by David S. Miller
parent 19936942a1
commit 49193a66f0
1 changed files with 17 additions and 1 deletions
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18
Documentation/networking/phy.txt
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@ -272,6 +272,8 @@ Writing a PHY driver
txtsamp: Requests a transmit timestamp at the PHY level for a 'skb'
set_wol: Enable Wake-on-LAN at the PHY level
get_wol: Get the Wake-on-LAN status at the PHY level
read_mmd_indirect: Read PHY MMD indirect register
write_mmd_indirect: Write PHY MMD indirect register
Of these, only config_aneg and read_status are required to be
assigned by the driver code. The rest are optional. Also, it is
@ -284,7 +286,21 @@ Writing a PHY driver
Feel free to look at the Marvell, Cicada, and Davicom drivers in
drivers/net/phy/ for examples (the lxt and qsemi drivers have
not been tested as of this writing)
not been tested as of this writing).
The PHY's MMD register accesses are handled by the PAL framework
by default, but can be overridden by a specific PHY driver if
required. This could be the case if a PHY was released for
manufacturing before the MMD PHY register definitions were
standardized by the IEEE. Most modern PHYs will be able to use
the generic PAL framework for accessing the PHY's MMD registers.
An example of such usage is for Energy Efficient Ethernet support,
implemented in the PAL. This support uses the PAL to access MMD
registers for EEE query and configuration if the PHY supports
the IEEE standard access mechanisms, or can use the PHY's specific
access interfaces if overridden by the specific PHY driver. See
the Micrel driver in drivers/net/phy/ for an example of how this
can be implemented.
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