site_archiver@lists.apple.com Delivered-To: darwin-kernel@lists.apple.com Thread-index: AcaGDHLGDnJR7lXsSlSC/0bLa/NPdwAM5QdA So that you don't have to cut n' paste the broken lines from you're email client, here the only parts of the URLs you actually need to locate the books: http://www.amazon.com/gp/product/0201549794 http://www.amazon.com/gp/product/0130313580 http://www.amazon.com/gp/product/0131429388 http://www.amazon.com/gp/product/0130981389 http://www.amazon.com/gp/product/013021034X -----Original Message----- From: darwin-kernel-bounces+bruce=iterative.com@lists.apple.com [mailto:darwin-kernel-bounces+bruce=iterative.com@lists.apple.com] On Behalf Of Michael Smith Sent: Friday, June 02, 2006 2:16 AM To: rohit dhamija Cc: darwin-kernel@lists.apple.com Subject: Re: cross-bounday memory communication b/w user app and theKernel.How? On Jun 1, 2006, at 9:06 PM, rohit dhamija wrote:

Thanks a lot for your comments !! Your suggestions are very good and valuable.

B/w i have one query ,

...

...

Create the IOMemoryDescriptors directly against the user-space addresses and do your I/O with those.

At this point i have memory of type IOMemoryDescriptor*. But Now I need to copy some information in this memory. So is it fine to copy using memcopy :to copy information in descr (of type IOMemoryDescriptor* ) ??

There is nothing to copy.

like

IOMemoryDescriptor * outDescriptor = NULL;

// Get the data into kernel space outDescriptor = IOMemoryDescriptor::withAddress( (vm_address_t)pComm->command_payload, sizeof(command_structure), kIODirectionOut, fClientTask);

now I need to copy some data into

so is it fine to do:

memcpy((void*)&outDescriptor, mydataBuffer, sizeof(MYDATABUFFER));

IF not, then how to copy/fill info in the descriptor ?

You don't. The descriptor refers to the buffer that already exists in the user-space process' address space. You don't need to copy anything. I want to ask "don't they teach you anything in school these days?" but perhaps that's a bit harsh. I would suggest that if you plan on doing much more work on device drivers that you should spend a little time reading up on the history and design of operating systems. There are a lot of fundamental things that it would really help you to know. Might I suggest: http://www.osxbook.com/ http://www.amazon.com/gp/product/0201549794/qid=1149228811/sr=1-7/ ref=sr_1_7/104-5530617-5549562?s=books&v=glance&n=283155 http://www.amazon.com/gp/product/0130313580/sr=8-1/qid=1149228772/ ref=pd_bbs_1/104-5530617-5549562?%5Fencoding=UTF8 http://www.amazon.com/gp/product/0131429388/qid=1149228811/sr=1-6/ ref=sr_1_6/104-5530617-5549562?s=books&v=glance&n=283155 http://www.amazon.com/gp/product/0130981389/qid=1149228870/sr=2-1/ ref=pd_bbs_b_2_1/104-5530617-5549562?s=books&v=glance&n=283155 http://www.amazon.com/gp/product/013021034X/qid=1149228906/sr=1-2/ ref=sr_1_2/104-5530617-5549562?s=books&v=glance&n=283155 I'm sure that you can get these books for considerably less elsewhere, it was just convenient to use Amazon to look them up. I'm also sure that other folks on this list will have their own suggestions; the above clearly shows my *nix background. = Mike _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/bruce%40iterative.com This email sent to bruce@iterative.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.a... This email sent to site_archiver@lists.apple.com