WiMAX stack and drivers for Intel WiMAX Link 5050

Intel would like to announce the initial release of a Linux WiMAX common stack and drivers for its WiMAX devices (eg: Intel(r) WiMAX/WiFi Link 5050, with estimated availability around third quarter of 2008).

The project follows a standard layered approach: a generic WiMAX kernel stack provides a common interface to control WiMAX devices. A user space daemon and libraries provide a high level API for control (network scanning, connection, disconnection, roaming management, etc) and access to the drivers.

Currently much of this higher level code is tailored to Intel's device, but we wanted to get it out as soon as possible.

You can find the code and additional information at
http://linuxwimax.org.

--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html

Code review occurs on patch submittable not by pointing developers off to an external project. Most likely there will be feedback that requires changes to API and other choices so you want to do this soon.
--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html

I know. Just wanted to get out the bits ASAP for whoever is interested to start looking at it.

I am pondering how to do this because there is a lot of code and I still don't have it ready for merging to mainline.

Eventually I'll have a git tree branching off netdev and will have to break up the kernel part in patchbombs for review & submission and fix stuff as we go.

Thanks,

I notice that there is a binary supplicant required. After the experience with the ipw3945 driver lack of acceptance, I would hope that Intel would have learned that dependence on binary userspace components would limit acceptance especially with other more hostile projects (OpenBSD).
--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html

This is the short (not in depth) code review of kernel component of Wimax.

Generic stack: drivers/net/wimax

1. Why spread those over 8 files of 100 lines each. Better to have a single file with 1000 lines and get reduced namespace and better compiler inlining etc.

2. The debug infrastructure is a mess of ugly macros that are unlikely to accepted in the current form, rework or delete it.

3. Use of sysfs for family and version ok, but why bother? Please don't build sysfs version checks into the API.

4. __wimax_flush_queue: is a nop, just remove

5. Stack is using generic netlink instead use newer netlink interface for management of devices: newlink/dellink instead see macvlan

i2400m hardware driver

1. sysfs
the inflight file is being used in a /proc style. Either change to one value per file or move to /proc/net/i2400m/ethX or better yet use debugfs /debugfs/i2400m/ethX/xxx

2. Use internal dev->stats for network stats (may not need get_stats at all)

3. No ioctl stub if not implemented

4. Use netdev_alloc_skb rather than alloc_skb for new code.

5. Use skb_copy_to_linear_data in i2400m_net_rx

6. Since hardware has to copy every received frame. Don't bother with checksum offload, the copy does the checksum for you and is safer.

7. Fine grain file organization in i2400m is bogus, put in one file and use proper name scope. Having 100 line files is unneeded

8. Fix the FIXME's?

9. Anyway to reuse existing usbnet infrastructure?

10. Since device is USB, Rx is in workqueue, so no need to go through netif_rx() softirq, should be able to go through netif_receive_skb

11. net_device and private data are zero on allocation, so no need for memset.

12. Since this is new code elminate all legacy ifdef's

Hi Stephen,

many thanks for having a look at the source code.

<snip>

I might have missed something in the latest code, but how it is using generic netlink for device management. The current code is using generic netlink for communication with the user space component. This includes task like scanning and association. The current kernel/user space API might need improvement, but I am not getting your point here. Please explain what you mean.

<snip>

I don't think so. WiMAX is not emulating an Ethernet device. It is an IP only networking interface.

You could have SDIO or PCI as a different transport.

Don't worry. We will do this before submitting it for mainline inclusion. It is a temporary solutions to help people that wanna test it with older kernels.

Regards

Marcel

Style difference, simplifies maintenance. Each file is logically grouped. Everything for doing X is in file X. I know you are a fan of big files, I am not :)

There is almost no inlining because each X only does stuff from itself. If there is a need for inlined stuff (I missed it) it should go to one of the header files --internal or external.

Ok, I'll figure a way to clean it up. Need to move most to inlines, still making sure anything that is disabled is compiled out.

family ID: it makes it easy to map device<->family-id without expensive look ups the kernel like an attribute with the device name would be. Rationale is most systems will have a single wimax device in the kernel. include/linux/wimax.h and drivers/net/wimax/id-table.c should have this documented...ouch, just remembered. The code drop out there shouldn't be as complete (documentation wise) as what I need to publish. Pls hold for it, will be available.

version: I anticipate the wimax API exported to user space is going to undergo a lot of changes while we all agree on what is the best interface. Because things might break, I want to make sure user space stuff can detect that and fail cleanly. Hence the versioning.

It is designed to be flexible so that adding new APIs allows old code to work (however, changing existing APIs is where it breaks). From the docs:

* Each WiMAX device exports two sysfs files declaring the generic
* netlink family ID associated to the interface and another one which
* version it supports. The version code has to fit in one byte
* (restrictions imposed by generic netlink); we use version / 10 for
* the major version and version % 10 for the minor. This gives 9
* minors for each major and 25 majors.
*
* The inexistence of any of this means the device does not support
* the WiMAX extensions.
*
* The version change protocol is as follow:
*

*

*
* Your user space code should not try to work if the major version it
* was compiled for differs from what the kernel offers. As well, it
* should not work if the minor version of the kernel interface is
* lower than the one the user space code was compiled for. *
* libwimax's wimax_open() takes care of all this for you.

Removed in newer code.

Geeze, I hide out for one week and a new system pops up?

What is the advantage of newlink dellink vs generic netlink? Pointers to doc? Generic netlink is fitting the bill pretty well as of now, so unless it is going away from the kernel, I feel we should not move it.

All that is gone from current tip.

Noted, will do.

Ack.

Any rationales for it? other than the padding and setting skb->dev, they seem the same.

Current tip code receives data from the device to an skb and then clones the different packets to deliver to netdev. This is not needed/done any more.

Again, style differences, a 10k file is already way too big for me.

En route, most of them fixed in tip.

Nope, the 2400 is a pure IP device (as Marcel mentioned). As well, we need to provide for using other bus connections (SDIO in the works), so that would break it up. OTOH, the hw protocol makes it different to plug into USBNET, as we can receive many packets in a single transaction.

Good point. Ack.

Ack

Done in tip.

We need to keep backwards compatibility to certain kernels for OSV support. ]Trying to make that as unobstrusive as possible. The git tip tree will be mostly backward-stuff clean.

Hey thanks a lot, this is great feedback

Inaky
--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Inlining gets more and more discouraged. Also longer term I would expect that gcc will do inlining over files anyways (it already supports that, but needs special support in the Makefiles which the kernel doesn't have). So even with inlining you wouldn't need to merge files or move code into headers.

It's still a bad way to do that (I agree with Stephen on that). Was also always a mess on wireless.

If you don't want expandable TLAs another better alternative to versions is ext2 style compatible/incompatible feature bitmaps.

-Andi

What is "TLA" ? Google gives me same Texas Library Organisation, Wikipedia also doesn't know.

Not sure what TLA stands for (probably type-length-attribute), but the concept is the same as TLV:
http://en.wikipedia.org/wiki/Type-length-value

Ain't that another way of saying versions? Sorry guys, but I am having a hard time understanding how the alternatives are better.

Expandable TLAs are fine, until we need to change the meaning of an existing field/value. Then there is no way to change it without breaking existing code other than create a new message. And then we have a mess like wireless again.

With simple versioning, we just bump up the major number and break. In user space, the libwimax shim library would take care of hiding this for the user if so is needed.

Inaky

It's a related way, but an actually sane way.

With compat/incompat bitmaps user space can actually make a educated decision if it should fail or not

-Andi

Inlining gets more and more discouraged. Also longer term I would expect that gcc will do inlining over files anyways (it already supports that, but needs special support in the Makefiles which the kernel doesn't have). So even with inlining you wouldn't need to merge files or move code into headers.

It's still a bad way to do that (I agree with Stephen on that). Was also always a mess on wireless.

If you don't want expandable TLAs another better alternative to versions is ext2 style compatible/incompatible feature bitmaps.

-Andi

With "pure IP", do you mean IPv4? Or do you mean "pure IPv4/IPv6"? If it is "pure IPv4", then WiMAX seems not future proof ...

It takes both. I guess what we should be saying is that it is not an ethernet-frame based device :) What you give the device is sent over to the base station, so it really is whatever the base station operator implements, which is mostly IP protocol (4, 6 or whatever).

Inaky

It's a pity that "Internet Protocol" (as in IPv4/IPv6) as well as "Intellectual Property" (as in IP-Core) have the same abbreviation.

;-)

Regards,
Chr.

Looking at the kernel/user interface: wimax-tools-1.1/lib/op-open.c

This API is repeating the mistake of the old Linux Wireless API. It is putting version checks between kernel and library and this is a maintenance nightmare. Linux API's are not COM. Versioning is a mistake. Use a TLA api like netlink so it can be extensible without version handshake.
--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html