Brylow is to be running a workshop with these, and possibly use them for classes. This was partially successful and I was able to document some important registers or flags, then use this to remove unneeded reads and writes from the device initialization code. After fixing this, the “kexec” code was able to start a new kernel. However, based on the Linux source code, in practice the polling actually happens entirely in hardware, between the host controller and the device. Perhaps not surprisingly, it turns out this is more complicated than I had hoped. Brylow and others have advertised Embedded Xinu as “ANSI C-compliant”; however it turns out that this is very much not the case, regardless of whether ANSI C means C90, C99, or C11, for many reasons some in new code we’ve added this summer, but also many in the existing code. Meanwhile, Farzeen continued to work on the graphical code, removing some of the older assembly files and fixing and additional additional functionality with C code.

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One ethernwt the hardware registers transfer size does not work as expected and a workaround had to be added. On a related note, I also noticed that some of the test code relied on signed overflow being fully defined as two’s complement arithmetic, but the corresponding ‘-fwrapv’ flag was missing from the compiler command line, so I added it.

[PATCH] net: Add ag7xxx driver for Atheros MIPS

To narrow the possible scope of the bug, I stripped out A7g1xx networking code, leaving just the USB and Ethernet drivers. Today I continued to try to solve the problem with the OS crashing after receiving too many Ethernet packets. The challenge with writing this documentation is making it complement the source code, rather than duplicate the information contained in it including in comments.

We also talked briefly about how the USB device model is incompatible with Xinu’s static device model as I mentioned in yesterday’s entry. The company selling them have many listings, and the price is good.

In the afternoon Tyler, Farzeen, and I met with Dr. There also seemed to be no documentation whatsoever about the vendor-specific commands, which may be foxes to actually set up the device to send and receive packets. Soylent Green Is People!

The main problem is that since we have been learning as we go, it has been difficult to split up the work.


This confirmed that the ethernet adapter does indeed work with Linux and that it is possible to access the Raspberry Fixs through the ethernet adapter without ethenret attached keyboard, monitor, or serial cable.

This is software-based polling, which is even more inefficient than the hardware-based polling that I was expecting to be available. The process worked perfectly by following instructions on this forum, with all expected messages etc from an Ubuntu machine but after the firmware image was uploaded the router always stayed on the Buffalo firmware.

The completion function can then take the appropriate action to handle the interrupt; for example, it might provide new mouse data fixea the kernel’s input subsystem. Towards this end we have already written a paper summarizing our work, we are working on writing new articles on the Embedded Xinu Wikiand I also improved the API documentation for many functions in the Embedded Xinu code-base that were not up to par, especially given that it is an educational operating system.

[source] ar71xx: prevent spurious ethernet resets from dma hang check false positives

When the request is completed, a callback function provided in the transfer request structure will be called. I have looked into what the Linux code does for DMA but it is very ag71xs to deal with all architectures, or all ARM architectures fixxes on the specific file and involves thousands of lines of code, so I haven’t yet been able to pick out the bits that are actually relevant for our purposes. Sma I was mostly waiting for Tyler and Farzeen to finish their sections of the paper and for Dr.

However, I was unable to confirm, through either the serial port or ethernet port, that this kernel had successfully booted in place of the default kernel. CFI does not contain boot bank location. I had no luck via tftp. These constants were defined as such because MIPS and many other platforms do consider ‘char’ to be signed.

As far as the OpenWRT devs have been able to determine, this chip revision is the only physical difference between our two units.

This is the preliminary to get interrupt-driven bulk transfers to work, which are required by any sane implementation of the ethernet driver otherwise there is no way for the system to be actually notified when fixse Ethernet packet is received. We began implementing the USB hub code in a separate file, usb-hub. The highest 2 bits of the bus address control caching behavior.


[PATCH] ar71xx: check for stuck DMA on ARx & fix sirq storm after recovery

This was crucial because over the past week or two I’ve had to change my understanding of what some of the registers do, thereby making some of the existing documentation I wrote incorrect or incomplete. With this configuration, the bug, or at least another bug with the same symptom, still occurred.

Two specific issues were a line of inline MIPS assembly language in the platform-independent part ag71cx reschedule function, and also an assumption that characters can be sent to the UART through kprintf before it has actually been initialized by the device-initialization code in sysinit apparently a quirk of the MIPS hardware.

As Xinu dmz supposed to be meant for education, I re-wrote this function to be as simple as possible, halving the lines of code excluding the detailed comments I added. I was initially confused about what this meant, because it makes it sound like interrupts from USB devices are not supported at all and system software must repeatedly poll USB devices for new input.

Although Farzeen, Tyler, and I wanted to do a combined talk to present our information in a more logical way and have time to demonstrate Embedded Xinu running on the Raspberry Pi, we’re required to all give ln individually. To fix this I added strlcpy to the C library and changed all offending strncpy calls to strlcpy.

Finally, we identified several problems with the UART driver; in particular, it accessed memory-mapped IO registers from C code without the proper ‘volatile’ annotations, and it was also written for the so-called “miniUART”, which is probably not the UART we want to be using, since existing software such as the “raspbootin” bootloader uses a different UART that appears to be more standard and better documented by the Broadcom documentation.

Today we mainly focused on understanding exactly what the USB driver is supposed to do after resetting the hardware. However, these memory attributes appear to be documented ib for TLB entries, which are irrelevant for Xinu because it does not use virtual addresses.