Question on switchdev
Subsystems (2)
Hi Jiri, Scott, or other switchdev experts,
TI Keystone netcp h/w has a switch. It has n slave ports and 1 host port. Currently the netcp driver disables the switch functionality which makes them appear as n nic ports. However we have requirement to add switch support in the driver. I have reviewed the experimental driver documentation Documentation/networking/switchdev.txt and would like to understand it better so that I can add this support to keystone netcp driver.
NetCP h/w has a 1 (host port) x n (slave port) switch. It can do layer 2 forwarding between ports. In the switch mode, host driver provides the frame to the switch and switch uses the filter data base (AKA ALE table, Address Learning Engine table) to forward the packet. There is a piece of information available per frame (meta data) to decide if frame to be forwarded to a particular port or use the fdb for forward decisions. I see following description in the above documentation.
===From Documentation/networking/switchdev.txt==================
On switchdev driver initialization, the driver will allocate and register a struct net_device (using register_netdev()) for each enumerated physical switch port, called the port netdev. A port netdev is the software representation of the physical port and provides a conduit for control traffic to/from the controller (the kernel) and the network, as well as an anchor point for higher level constructs such as bridges, bonds, VLANs, tunnels, and L3 routers. Using standard netdev tools (iproute2, ethtool, etc), the port netdev can also provide to the user access to the physical properties of the switch port such as PHY link state and I/O statistics.
=================================================================
1. How does port netdev differ from regular netdev that carries data when registering netdev? Any example you can point to?
2. I assume port netdev will appear as an interface in ifconfig -a command and it is not assigned an IP address. Correct?
3. with 1xn switch, so we have n + 1 netdev registered with net core? I assume, only 1 netdev is for data plane and the rest are control plane. Is this correct?
4. We have bunch of port specific configuration that we would like to control or configure from use space using standard tools. For example, switch port state, flow control etc. Is that possible to add using this framework? ethtool update needed for this?
5. This feature is marked as experimental. Hope having more drivers added to this switch dev framework can eventually get this out of experimental to regular status. Right?
I have more questions that I will defer for now. It would be great if I can work with you to implement this in netcp driver. Hope you can respond with your comment.
Thanks.
Signature · 2 lines
Murali Karicheri Linux Kernel, Keystone
On Mon, Feb 29, 2016 at 04:43:16PM -0500, Murali Karicheri wrote:
Hi Murali
Please can you get your email client to wrap lines at ~ 75 characters.
Quoted 8 lines
TI Keystone netcp h/w has a switch. It has n slave ports and 1 host port. Currently the netcp driver disables the switch functionality which makes them appear as n nic ports. However we have requirement to add switch support in the driver. I have reviewed the experimental driver documentation
Documentation/networking/switchdev.txtand would like to understand it better so that I can add this support to keystone netcp driver.
Quoted 7 lines
NetCP h/w has a 1 (host port) x n (slave port) switch. It can do layer 2 forwarding between ports. In the switch mode, host driver provides the frame to the switch and switch uses the filter data base (AKA ALE table, Address Learning Engine table) to forward the packet. There is a piece of information available per frame (meta data) to decide if frame to be forwarded to a particular port or use the fdb for forward decisions.
This makes is sound like a good fit for DSA.
Documentation/networking/dsa/dsa.txt.
You probably need to implement a new tagging protocol in net/dsa/tag_*.c and a driver in drivers/net/dsa/
Quoted 2 lines
1. How does port netdev differ from regular netdev that carries data when registering netdev? Any example you can point to?
They don't differ at all. You consider each port of the switch to be a normal Linux interface.
Quoted 2 lines
2. I assume port netdev will appear as an interface in ifconfig -a command and it is not assigned an IP address. Correct?
The user can assign an address, if they want. It is a normal Linux interface. They can also create a bridge, and add the interface to the bridge. An advanced DSA driver will keep track of which interfaces are in which bridge, and if possible, offload the bridge to the hardware.
Quoted 3 lines
3. with 1xn switch, so we have n + 1 netdev registered with net core? I assume, only 1 netdev is for data plane and the rest are control plane. Is this correct?
No. You only have netdev devices for the external ports of the switch. The other port is known as the cpu port, and does not have a netdev.
Quoted 4 lines
4. We have bunch of port specific configuration that we would like to control or configure from use space using standard tools. For example, switch port state, flow control etc. Is that possible to add using this framework? ethtool update needed for this?
The whole idea here is that the switch ports are normal Linux interface. You use normal linux APIs to configure them. You probably don't need to add any new features.
One key things to get your head around. The switch is a hardware accelerator for the Linux stack. You have to think how you can make your switch accelerate the Linux stack. It takes people a while to get this.
Andrew
Quoted 5 lines · Andrew Lunn
On Mon, Feb 29, 2016 at 04:43:16PM -0500, Murali Karicheri wrote:
Hi Murali
Please can you get your email client to wrap lines at ~ 75 characters.
Hi Andrew,
Thanks for responding. I have tried the instruction below and it doesn't seem to work for me. Do you know what will I have to set in thunderbird to do this?
http://arapulido.com/2009/12/01/enabling-line-wrapping-in-thunderbird/
Quoted 16 lines
Quoted 8 lines
TI Keystone netcp h/w has a switch. It has n slave ports and 1 host port. Currently the netcp driver disables the switch functionality which makes them appear as n nic ports. However we have requirement to add switch support in the driver. I have reviewed the experimental driver documentation
Documentation/networking/switchdev.txtand would like to understand it better so that I can add this support to keystone netcp driver.Quoted 7 lines
NetCP h/w has a 1 (host port) x n (slave port) switch. It can do layer 2 forwarding between ports. In the switch mode, host driver provides the frame to the switch and switch uses the filter data base (AKA ALE table, Address Learning Engine table) to forward the packet. There is a piece of information available per frame (meta data) to decide if frame to be forwarded to a particular port or use the fdb for forward decisions.
Quoted 3 lines
This makes is sound like a good fit for DSA.
Documentation/networking/dsa/dsa.txt.
Let me check and get back to you on this and below after reading the above.
Murali
Quoted 42 lines
You probably need to implement a new tagging protocol in
net/dsa/tag_*.cand a driver indrivers/net/dsa/Quoted 2 lines
1. How does port netdev differ from regular netdev that carries data when registering netdev? Any example you can point to?
They don't differ at all. You consider each port of the switch to be a normal Linux interface.
Quoted 2 lines
2. I assume port netdev will appear as an interface in ifconfig -a command and it is not assigned an IP address. Correct?
The user can assign an address, if they want. It is a normal Linux interface. They can also create a bridge, and add the interface to the bridge. An advanced DSA driver will keep track of which interfaces are in which bridge, and if possible, offload the bridge to the hardware.
Quoted 3 lines
3. with 1xn switch, so we have n + 1 netdev registered with net core? I assume, only 1 netdev is for data plane and the rest are control plane. Is this correct?
No. You only have netdev devices for the external ports of the switch. The other port is known as the cpu port, and does not have a netdev.
Quoted 4 lines
4. We have bunch of port specific configuration that we would like to control or configure from use space using standard tools. For example, switch port state, flow control etc. Is that possible to add using this framework? ethtool update needed for this?
The whole idea here is that the switch ports are normal Linux interface. You use normal linux APIs to configure them. You probably don't need to add any new features.
One key things to get your head around. The switch is a hardware accelerator for the Linux stack. You have to think how you can make your switch accelerate the Linux stack. It takes people a while to get this.
Andrew
Signature · 2 lines
Murali Karicheri Linux Kernel, Keystone
Quoted 30 lines · Murali Karicheri
Quoted 5 lines · Andrew Lunn
On Mon, Feb 29, 2016 at 04:43:16PM -0500, Murali Karicheri wrote:
Hi Murali
Please can you get your email client to wrap lines at ~ 75 characters.
Hi Andrew,
Thanks for responding. I have tried the instruction below and it doesn't seem to work for me. Do you know what will I have to set in thunderbird to do this?
http://arapulido.com/2009/12/01/enabling-line-wrapping-in-thunderbird/
Quoted 16 lines
Quoted 15 lines
TI Keystone netcp h/w has a switch. It has n slave ports and 1 host port. Currently the netcp driver disables the switch functionality which makes them appear as n nic ports. However we have requirement to add switch support in the driver. I have reviewed the experimental driver documentation
Documentation/networking/switchdev.txtand would like to understand it better so that I can add this support to keystone netcp driver.NetCP h/w has a 1 (host port) x n (slave port) switch. It can do layer 2 forwarding between ports. In the switch mode, host driver provides the frame to the switch and switch uses the filter data base (AKA ALE table, Address Learning Engine table) to forward the packet. There is a piece of information available per frame (meta data) to decide if frame to be forwarded to a particular port or use the fdb for forward decisions.
Quoted 53 lines
Quoted 3 lines
This makes is sound like a good fit for DSA.
Documentation/networking/dsa/dsa.txt.Let me check and get back to you on this and below after reading the above.
Murali
Quoted 42 lines
You probably need to implement a new tagging protocol in
net/dsa/tag_*.cand a driver indrivers/net/dsa/Quoted 2 lines
1. How does port netdev differ from regular netdev that carries data when registering netdev? Any example you can point to?
They don't differ at all. You consider each port of the switch to be a normal Linux interface.
Quoted 2 lines
2. I assume port netdev will appear as an interface in ifconfig -a command and it is not assigned an IP address. Correct?
The user can assign an address, if they want. It is a normal Linux interface. They can also create a bridge, and add the interface to the bridge. An advanced DSA driver will keep track of which interfaces are in which bridge, and if possible, offload the bridge to the hardware.
Quoted 3 lines
3. with 1xn switch, so we have n + 1 netdev registered with net core? I assume, only 1 netdev is for data plane and the rest are control plane. Is this correct?
No. You only have netdev devices for the external ports of the switch. The other port is known as the cpu port, and does not have a netdev.
Quoted 4 lines
4. We have bunch of port specific configuration that we would like to control or configure from use space using standard tools. For example, switch port state, flow control etc. Is that possible to add using this framework? ethtool update needed for this?
The whole idea here is that the switch ports are normal Linux interface. You use normal linux APIs to configure them. You probably don't need to add any new features.
One key things to get your head around. The switch is a hardware accelerator for the Linux stack. You have to think how you can make your switch accelerate the Linux stack. It takes people a while to get this.
Andrew
Andrew,
Quoted 1 line
From the high level, it looks like netcp switch meets the specifications
of a DSA hardware. Can you point me to a specific implementation that I can use as an example to implement this for netcp?
Signature · 2 lines
Murali Karicheri Linux Kernel, Keystone
Quoted 5 lines
Andrew,
Quoted 1 line
From the high level, it looks like netcp switch meets the specifications
of a DSA hardware. Can you point me to a specific implementation that I can use as an example to implement this for netcp?
You need two parts:
A tagging implementation, in net/dsa/tag_*.c. They are all pretty similar, and all pretty simple.
A switch driver. driver/net/dsa/mv88e6060.c is the simplest. I would suggest your first submission implements similar features as to what this driver does. This is very minimalistic, but a good start. Once that is accepted, you can incrementally add more features.
Andrew
Quoted 11 lines · Andrew Lunn
Quoted 5 lines
Andrew,
Quoted 1 line
From the high level, it looks like netcp switch meets the specifications
of a DSA hardware. Can you point me to a specific implementation that I can use as an example to implement this for netcp?
You need two parts:
A tagging implementation, in
net/dsa/tag_*.c. They are all pretty similar, and all pretty simple.
Quoted 7 lines
A switch driver.
driver/net/dsa/mv88e6060.cis the simplest. I would suggest your first submission implements similar features as to what this driver does. This is very minimalistic, but a good start. Once that is accepted, you can incrementally add more features.Andrew
Thanks Andrew!
Signature · 2 lines
Murali Karicheri Linux Kernel, Keystone