Do we really need to touch the framework for this? I'm of the opinion
that these debugging overrides might better be handled as driver-private
tunables ("private properties"), without making the framework aware of
them explicitly.
Admittedly, its not that big a deal one way or the other....
- Garrett
Sebastien Roy wrote:
> I'm sponsoring this fast-track for Vasumathi Sundaram, the timer expires
> on 06/15/2009.
>
> LSO and HW TX Checksum properties in dladm
> ------------------------------------------
>
> 1. Summary
> ----------
>
> This case proposes to add two properties "lso" and "hw_tx_cksum" to
> dladm, to allow the LSO and Transmit HW checksum properties of the
> driver to be updated on the fly at runtime.
>
> Release binding:
> Patch
>
> 2. Description
> --------------
>
> To ensure the correct operation of any driver that supports LSO and
> hardware checksum, it is often required to turn the properties on or
> off for debugging. An example will be the nxge driver, that has
> different values for the hardware checksum capability to workaround
> hardware bugs.
>
> Currently, to enable/disable the Transmit HW checksums and LSO
> properties in a driver, the driver's .conf file needs to be updated to
> set the capabilities, and the interface has to be unplumbed and
> plumbed for the settings to take effect. When the interface is
> replumbed, the driver announces its LSO/HW Checksum capabilities to
> GLD which is then passed up to its clients.
>
> Since dladm provides more consistent interfaces to set link
> properties, LSO and TX HW checksum should be added as link properties
> that can be enabled or disabled at runtime without requiring to modify
> the driver's .conf file and the unplumb/plumb sequence.
>
> To support this, the command 'dladm show-linkprop' will now display
> two additional properties "lso" and "hw_tx_cksum" for each driver.
> This is achieved by adding two new MAC properties MAC_PROP_LSO and
> MAC_PROP_HCKSUM to the enum mac_prop_id_t in
> /usr/src/uts/common/sys/mac.h. These properties will apply to all
> datalinks of type DL_ETHER.
>
> Each driver that supports LSO and TX Hardware checksum should include
> cases for MAC_PROP_LSO and MAC_PROP_TX_HCKSUM in <driver>_m_setprop()
> and <driver>_m_getprop() callback functions to set and get the current
> and possible values. dladm will not list these properties for those
> drivers that do not support them. Whenever one of these properties is
> enabled or disabled through <driver>_m_setprop(), the driver should
> call mac_capab_update (MAC_NOTE_CAPAB_CHG) to initiate capability
> renegotiation with upper layers, which prevents the needs for the
> unplumb-plumb of the interface.
>
> 3. Interface changes
> --------------------
>
> | Interfaces Exported |
> |______________________|__________________________|_______________________|
> | Interface | Classification | Comments |
> |______________________|__________________________|_______________________|
> | | | |
> | MAC_PROP_LSO | Consolidation Private | <sys/mac.h> |
> | MAC_PROP_HCKSUM | Consolidation Private | <sys/mac.h> |
> | lso | Committed | dladm property name |
> | hw_tx_cksum | Committed | dladm property name |
> |______________________|__________________________|_______________________|
>
>
> A sample output is as follows:
> LINK PROPERTY PERMS VALUE DEFAULT POSSIBLE
> e1000g0 lso rw 1 1 1,0
> e1000g0 hw_tx_cksum rw 1 1 1,0
>
>
>
