From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@labs.coraid.com>
Date: Fri,  1 Oct 2010 16:24:21 -0400
To: 9fans@9fans.net
Message-ID: <acbbbd521c91ac93a1c0f6fbb5eabc52@coraid.com>
In-Reply-To: <10bf630b13fbac21955790c6827f1ab4@quintile.net>
References: <10bf630b13fbac21955790c6827f1ab4@quintile.net>
MIME-Version: 1.0
Content-Type: text/plain; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
Subject: Re: [9fans] stupid kernel question
Topicbox-Message-UUID: 5c0b1ebe-ead6-11e9-9d60-3106f5b1d025

On Fri Oct  1 15:25:16 EDT 2010, steve@quintile.net wrote:
> how does kernel code call plan9 system calls, does it perform a
> trap from kernel back into kernel space and make the request just
> like a user process or is there a more direct, subtle route?

the short answer is that it doesn't.  but read/write/open/close/stat
are done via channels, and often with Blocks.  for example
(hopefully without typos)

	c = namec("/sys/src/9/pc/mkfile", Aopen, OREAD, 0);		/* can call error */
	b = devtab[c->type]->bread(c, 64*1024, 0);
	/* b->wp points to data if successful BLEN(b) is the length */

- erik