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• Device Drivers for Linux Gazette

Device Drivers for Linux Gazette

Hi. Just dicovered Linuxgazette today. This is a really great site.

If you are looking for article ideas, I'd like to see an article, or even series, on writing device drivers for Linux. This is a topic I have found very little information about on the net.

Just my two cents.

Writing the Linux kernel's device driver interfaces are enough of a subject to fill a whole book. Maybe the O'Reilly Writing Linux Device Drivers (by Allessandro Rubini) and their Understanding the Linux Kernel by Daniel Pierre Bovet (among others) would be a good choice for you.

As for documention online: You could always read the sources, copy and paste parts of the Makefiles, copy an existing (similar) device driver and edit. I realize that this is a horrible oversimplification; but that's how must of the Linux kernel hackers started.
-- JimD

how to write a parallel port device driver,ie, interrupt driven. Not, for printer, but,for general device connected to EPP port..?

If you need something to be interrupt driven than you need a kernel module. You might be able to have a very simple kernel module that simply relays the interrupt as a character through a device node. Then you could have a user space process listening...

[ Some guesses about the nature of poll() and select(), trimmed. ] Please post a message to a good linux programming newsgroup for better details. Actually I've posted an abstracted version of this question to the comp.os.linux.development.system newsgroup on your behalf. So, perhaps there's already an answer waiting...
-- JimD

Well, the Answer Guy is just barely getting into this subject, so for this topic, he's a newbie like the rest of us. It looks like some of our weekend mechanics really want to get down into the spark plugs, there. So, if anyone feels inclined to write a down and dirty device driver article that explains a bit of deep wizardry in plain english, especially if it covers something that's new in the 2.4 series kernels, we'd love to publish it. -- Heather

Or if anybody would like to dissect and explain a small driver they've written, that would also make a good article. -- Mike

• Great
• Subscribing to LG
• Your writing of: "Integrating" Linux/sendmail with MS Exchange
• Thank you
• incensative, and down right rude,

Great

Great April edition. Thanks a lot. Keep up the good work (and the interesting topics).

Thanks for reading us, Jim! -- Heather

Subscribing to LG

Finally, a way to subscribe to Linux Gazette!

Debian has long had the lg-issue## packages. Now it has a couple new packages:

• lg-subscription : install new issues as they arrive.
• lg-ltest-two : install the latest two issues and remove older ones.
• lg-all : install all of the currently-available issue.

Of course, it adds/removes packages only when you do a general package update. Note that these programs are supported by Debian, not by LG.

-- Mike (your friendly Linux Gazette Editor)

Looks like you have to get it from testing (aka woody) or unstable (aka sid) but at least it shouldn't require a libc update, if you temporarily add one of these to your sources list to get them. If one of these does ask for a libc change, it's a packaging bug and you should report it immediately.

But be especially careful to change things back, or you may find yourself in for a big surprise when you run "apt-get upgrade" to catch the latest security patches. -- Heather

Your writing of: "Integrating" Linux/sendmail with MS Exchange

Hi,

Just a note of constructive criticism.

I just read a copy of your writing of "Integrating" Linux/sendmail with MS Exchange, on this site.

http://lhd.datapower.com/LDP/LDP/LG/issue38/tag/5.html

It's something you wrote in 1999, so you may be writing differently now. If so, please disregard this letter.

What you are about to say is still valuable as a reminder to new members of the Answer Gang, potential article authors, and in fact just about anybody who hopes to be a very vocal Linux advocate. So I hope you don't mind that we've published it anyway. -- Heather

Although I found this information helpful, you appear to have trouble staying on track with the useful information, and like to get off subject with the Microsoft bashing.

I do use Microsoft products, as well as Linux and AIX products, and understand your point of view (even agree with most, if not all, of it).

My constructive criticism is that you should refrain from the Microsoft bashing or at least keep it to one line, and keep more to the point of trying to relay useful information. (I'm assuming that is what you are really trying to do.)

If someone is having trouble with something like integrating sendmail and exchange, they may not have a choice about what systems or software to use, and just need some well written, detailed information, not an anti-Microsoft commercial.

- Dave

Thanks, Dave. Issue 38 was a long time ago now.

The Answer Gang now includes a number of more cheerful sorts in addition to the curmudgeonly Answer Guy himself. One or two even still use Windows for some of their work. (Note: we avoid answering Windows questions at all, unless they're really about working with Linux environments.) Having more of us frees the ones who really don't want to touch anything about MS, from even having to answer. Also, a heavier editorial hand is being applied now.

As for myself, I look forward to the day when systems will be sufficiently easy to use that it will not be clear... nor terribly necessary to know... which OS is chugging along "under the hood". I don't think that day is at all close but I look forward to it anyway.

-- Heather

Thank you

Dear Mike

I want to take the opportunity to thank you very much for the feed back and for taking the time to give me the information.

incensative, and down right rude,

sorry pal, but after reading your reponse to a post for help, i couldnt help but send you this note about what an [ rude word deleted ] you must be...and would be very much surprised if anyone would want you on the payroll....

respectfully,
joe agate

http://rpmfind.net/linux/mdw/LDP/LG/issue50/tag/33.html

[ HTML version of same text, also deleted ]

Curiously, he chose to "rag" on the Answer Guy for one of his clearer answers to an unclear question. He calls him a bad name, then signs off "respectfully". Right.

Is it really "insensitive" to mention that LG has a search engine (http://www.linuxgazette.net/search.html)? Nope, I think not.

Is it "insensitive" to ask that querents mention what they've tried already? Maybe - but it's a fact of life in tech support, most people say "it's broken" not "I tried this, and that, and the other thing, and... yada yada ... anyways so you can see I tried everything, and it hates me". In plain verbal conversation it's rude to maunder on like that, so people tend not to do it. In tech support, the more info you can send us (that is related to the question) the better we can help. If this were a phone call, we could have this merry back and forth, and it still probably wouldn't take an hour. At typical Answer Gang speeds though... more info will help you as much as it helps us.

Is it "insensitive" to suggest that the poor bloke may have to buy a new card or new server? Probably. Oh well. Life's tough that way sometimes. Turns out that he's probably okay, according to another reader who assured us that the Jotan is indeed a Trident relative.

Is it insensitive to send us the same text as both plaintext and HTML? No, usually it just means someone didn't know how to turn off this "feature" (cough cough. cough. no, I'm okay. cough cough. water. Ahem) in MS Outlook. Try this great answer from Chris G. in last month's Answer Gang:

http://linuxgazette.net/issue65/tag/8.html

Lastly, I'm pretty sure it's insensitive to publish this, but Joe, you mailed us, and this is what we normally do with letters to the editors. Let us know when you have a linux question, and we'll try to answer it -- if you give us enough information!

Linux jobs

Would it be possible for someone at your publication to provide me with a resource as to where I could locate an experienced Linux programmer for the Tampa Florida area. Is there a website for Linux job postings or a publication that I might be able to contact. I would appreciate any help that you could give me.

The Answer Gang published a list of sites for job searchers in the last issue. I'm sure you can post openings at these sites as well.

http://linuxgazette.net/issue65/lg_answer65.html#tag/greeting

LG does not publish job listings because they are so temporary in nature: the job may be filled by the time the issue is published!
-- Mike

To repeat from last time:

You can check out Linux Journal's Career Center (http://www.linuxjournal.com/employ), Geekfinder (http://www.geekfinder.com), the Sysadmin's Guild (SAGE) Job Center (http://www.usenix.org/sage/jobs/sage-jobs.html), or pay attention to your local area papers for when major high tech Job Fairs are in your area, so you can go to them. There are also some really generic job sites like Dice.Com (http://www.dice.com) or MonsterBoard (http://www.monsterboard.com). If you hate the corporate mold, check out some of the project offers at Cosource (http://www.cosource.com) or Collab.Net (http://www.collab.net). Or put up your consulting shingle by listing yourself at Linuxports (http://www.linuxports.com) and getting listed into a few search engines.

... and expand a little:

When I went to Google! and typed in the keywords:
linux jobs

-- it claimed it has about 400 entries.

As Mike noted, many of these allow employers to post job offers, as well as having jobseekers post resumés.
-- Heather

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Published in issue 66 of Linux Gazette May 2001

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