Re: [Ocf-linux-users] driver for micronas aes-7108

[David M. <Dav...@se...>]

Jivin Max lays it down ...
> Hello.
> 
> I tried to port driver for micronas cypher chip from old ocf version to
> latest release. I'm not sure if I did it properly but at least it
> compiles now.

Sorry I've been so slow to respond,  bit busy here on some stuff.

Comments included below.

> /* Runtime mode */
> static int c7108_crypto_mode = C7108_AES_CTRL_MODE_CTR;
> //static int c7108_crypto_mode = C7108_AES_CTRL_MODE_CBC;

You probably want CBC mode for OCF use,  unless you don't ;-)

> static void
> skb_copy_bits_back(struct sk_buff *skb, int offset, caddr_t cp, int len)
> {
> 	int i;
> 	if (offset < skb_headlen(skb)) {
> 		memcpy(skb->data + offset, cp, 
> 		       min_t(int, skb_headlen(skb), len));
> 		len -= skb_headlen(skb);
> 		cp += skb_headlen(skb);
> 	}
> 	offset -= skb_headlen(skb);
> 	for (i = 0; len > 0 && i < skb_shinfo(skb)->nr_frags; i++) {
> 		if (offset < skb_shinfo(skb)->frags[i].size) {
> 			memcpy(page_address(skb_shinfo(skb)->frags[i].page) +
> 			       skb_shinfo(skb)->frags[i].page_offset,
> 			       cp, min_t(int, 
> 					 skb_shinfo(skb)->frags[i].size, len));
> 			len -= skb_shinfo(skb)->frags[i].size;
> 			cp += skb_shinfo(skb)->frags[i].size;
> 		}
> 		offset -= skb_shinfo(skb)->frags[i].size;
> 	}
> }

You can remove this function in newer OCF versions and switch to using
crypto_copyback instead,  check the other driver for usage,  it's
pretty simple.

crypto_copyback handles all the SKB/IOV/buffer variants for you.

> 	/* Start AES cipher */
> 	c7108_reg_wr16(C7108_AES_CTRL, ctrl | C7108_AES_GO);
> 	
> 	//printk("Ctrl: 0x%x\n", ctrl | C7108_AES_GO);
> 	do {
> 	    /* TODO: interrupt mode */
> 	    //        printk("aes_stat=0x%x\n", stat);
> 	    //udelay(100);
> 	} while ((cnt++ < 1000000) && 
> 		 !((stat=c7108_reg_rd16(C7108_AES_CTRL))&C7108_AES_OP_DONE));


While polling is ok for a quick hack you will be much better off with
an interrupt based solution.  Probably based on the hifn/safe or tolapai
drivers.  Might be worth adding a call to schedule() inside this loop so
that you do not completely lockup the system if it takes a long time.

Otherwise it's a start towards getting something going.

The big thing is getting it to crypt something correctly.
I usually run something like:

	echo test-data | openssl aes-128-cbc -k test-key | hd

using both cryptosoft and a new driver until I get the same result
from the new driver ;-)

Cheers,
Davidm

-- 
David McCullough,  dav...@se...,  Ph:+61 734352815
McAfee - SnapGear  http://www.snapgear.com                http://www.uCdot.org