Posts

Showing posts from July, 2008

The TeXTing Swindle

I recently started communicating with some family via "texting", because, for reasons I don't fully understand, they will happily respond to a text message (and send them out on their own), but won't answer a regular phone. So ignoring the annoyance of trying to draft up a message on the toy 10 key keypad on my phone -- which takes approximately 20 times as long as it would to say the same thing in a voice call, I started thinking about the economics behind the texting fad. My provider charges me $0.20 per text message. My overlimit minutes cost about $0.25. (Picture messages cost more -- $1.95 each, I think.) This is the biggest swindle made by phone companies in recent history. Look at the data involved. A phone call (voice message) takes the following bit of bandwidth: Assume 8-bit ULAW or ALAW sampling (12 bits compressed to 8 bits) Assume 8 kHz sampling, which is typical for "phone quality" audio That gives up 8 * 8000 = 64,000 bits per second o

New Experimental AudioHD Driver

I've just posted the latest experimental version of the OpenSolaris audiohd driver. This driver includes the latest work from the engineers in Beijing, including a widget parser that enables the driver to work on a much larger variety of audio configurations. As most motherboards these days ship with an audiohd compliant device, this should greatly expand the support for audio on Solaris systems. The above driver binary also includes suspend/resume support. Note that this is not the anticipated Open Sound System driver, but rather an extension of the pre-existing Sun driver. It won't work with OSS. However, there is some chance (I've not tested it myself) that this will even work on Solaris 10. A webrev of the changes should be posted soon. In the meantime, if you want to give this a whirl, let me know the results. (To test it, just copy the binary objects into /kernel/drv/amd64/ or /kernel/drv and reboot. -- Yes there are ways to do this without a reboot, but th

NIC driver family trees

This may be interesting to some people -- and its recorded here for posterity. A number of NIC drivers in Solaris have been developed using "copy-paste" approaches. As a result, there are a couple of family "lines" for NIC drivers. le (ancient 10 Mbit only) driver, is the common root for one heritage. From le was developed hme. From hme were developed qfe, eri, and gem. From these was developed ce. And ultimately, from these was developed nxge (although nxge shares little with its ancestors anymore.) Another heritage goes back to ancient dnet (tulip) drivers on x86. dnet begat dmfe, which begat bge. There are probably other drivers that bge spawned, but its hard to know for sure how much copying may have occurred. afe and mxfe were developed pretty much independently from the others, although afe was developed first, and begat mxfe (which is for very similar hardware -- a good counter example for a case where copying the code made sense -- of course I'

Cut & Paste Device Driver Design

A common approach to device driver design is to start with a device driver for a similar piece of hardware that someone else wrote, and copy it, then modify it. However, this approach is fraught with peril, and I thought it might be a good idea to record my thoughts on this for posterity. If this post saves just one future developer from falling into this pit, it will have been worthwhile. The first problem is that most device drivers have a number of non-trivial "features" in them that relate to the specific issues of a particular piece of hardware. Often this means that there are internal design features of the driver that are not ideal for a new driver. (A classic example would be nxge's use of particular hacks relating to the location of it in relation to the IOMMU on certain Niagra processors. No other driver is ever going to need that.) The second problem is that most device drivers are not 100% bug free. The copy-modify approach to coding tends to lead to b