May 2011 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Linux kernel test suites
by Abu Rasheda May 23, 2011

May 23, 2011

Can someone pass me pointer to Linux kernel test suite ? I am specially interested in iptables (netfilter) and socket APIs. Thanks

4 4

how to download a specific kernel version from kernel.org
by sandeep kumar May 23, 2011

May 23, 2011

Hi all, I want to download kernel version 2.6.35 for a specific reason. I have a patch which is to be applied to that specific kernel revision. But in kernel.org i m finding only 2.6.35.13 only.(May be i cudnot find it) Pls tell me How to download that? Thanks in advance.. -- With regards, Sandeep Kumar Anantapalli,

4 3

Question about MFD devices.
by jocke＠holstenhof.se May 23, 2011

May 23, 2011

Hi! I'm trying to do a simple driver on an embedded (ARM) system that needs to access some functionality in an MFD device. I've deducted that my driver needs to be integrated into the MFD device structure, otherwise I won't really be able to access the required functions. I've been trying to figure out why we have these MFD devices, but I don't see the logic behind them. To me, they mailny seem to duplicate the standard kernel driver structure, and it doesn't seem like the provided functionality should be used in-kernel. I guess that my conclusion are way wrong, so I hope that someone on the list can enlighten me about this. BRs, /Jocke!

1 0

Virtual memory question
by Naman shekhar Mishra May 23, 2011

May 23, 2011

Is the last gigabyte in the virtual address space of each process mapped to the same memory location (which starts from the 2nd megabyte of physical RAM)? And, what happens when a process makes a system call - does the kernel work on behalf of the process, i.e. use the process page tables, or uses its own page tables for virtual addressing. If the former is true, when are the kernel page tables used?

2 1

help on skb functions
by sugnan prabhu May 23, 2011

May 23, 2011

Hi, I have working on the tunnel networking driver. My requirement is to perform operation, which is opposite to the skb_put. following is the code i have written. if (tunnel->skb == NULL) { int len; tunnel->skb = netdev_alloc_skb(dev, sizeof(struct myprotocol_hdr)); /*Place holder for the mhdp packet count*/ len = skb_headroom(tunnel->skb); skb_push(tunnel->skb, len); memset(tunnel->skb->data, 0, len); * **tunnel->skb->tail -= len;* * **tunnel->skb->len -= len;* } hdr_data = (struct data_info *) skb_put(tunnel->skb, sizeof(struct data_info)); Every time before calling the dev_queue_xmit i check whether the hardware is busy? if it is, then i call skb_put and add a structure at the end of header. you can observe that, for the first time skb is allocated, skb->tail and skb->len are being decremented manually in order to avoid memory copy(as the structure is added at the end of previous header). Is there any better function which can used instead.

1 0

revisiting scullpipe implementation
by Ezequiel García May 23, 2011

May 23, 2011

Hi everybody, I don't know if anyone cares about this subject. But here it goes anyway. I've been reading through the excellent Linux Device Driver book (third ed.) for the past months. I have decided to give it a try to the drivers samples, starting by scull. After some minor updates (mostly related to new mutex interface), I started playing with scull and scullpipe. The thing is the scullpipe implementation makes buffer initialization, and sets read and write pointer to zero at device open. Acordingly, it releases the buffer at device close. This implementation makes this possible: (first, on one terminal) $ cat /dev/scullpipe0 (second, another) $ dd if=/dev/zero of=/dev/scullpipe0 bs=512 count=1 But not the other way round: (first, write) $ dd if=/dev/zero of=/dev/scullpipe0 bs=5000 count=5 (then, read) $ cat /dev/scullpipe0 Because when the reader (cat) opens the device the read/write pointers are made equal and buffer looks empty. (Besides, the buffer resets itself on device release; so it does not persist when nobody is using it.) Questions: Did I misunderstand the driver's idea and this behavior is not buggy, or ... is the code just aimed at learning so it does not matter? Actually it is pretty easy (and good training for starters) to change it. I had to move some code from device open to device init and from device release to device clean_up. Maybe someone is reading the book and might be interested. Greetings, Ezequiel.

1 0

Fixmap of virtual address
by J.Hwan.Kim May 22, 2011

May 22, 2011

Hi, everyone What's the purpose of fixmap and when is the fixmap used? Is there fixmap routine in ARM architecture? I found fixmap_address enum type in many architecture but not in ARM. If fixmap is not used in ARM, why? Thanks in advance. Best Regards, J.Hwan Kim

1 0

Linux wireless support education video on YouTube
by julie Sullivan May 21, 2011

May 21, 2011

For those of you that don't have the time to follow the high-volume linux-kernel mailing list Luis Rodriguez posted the following yesterday which some on kernel-newbies may find helpful: > If you have engineers who need to support the 802.11 Linux subsystem > you at times see yourself needing to educate each group through some > sessions. In hopes of reusing educational sessions I've decided to > record my own series and post it on YouTube. I've broken down each > logical component of the series into as small atomic pieces so we can > add / remove / update the series into a new baked improved playlist. > If you wish to contribute to this please feel free to send me your own > videos so I can extend the series. > > The hope is to education engineers as quickly as possible and then > refer them to our wireless.kernel.org wiki for more information. The > playlist of the 4 videos is available via: > > http://bit.ly/kYdfpg > > There will be Q&A Session on May 25, 2011 at 8am PST, you can poke us > with questions on IRC: > > IRC server: irc.freenode.net > Channel: #linux-wireless > > The breakdown of the series covers: > > * Review of the 802.11 subsystem > * Development process review > * Daily snapshots / stable release of compat-wireless > * Debugging 802.11 drivers > * 802.11s review > > PS. Thanks to Javier for providing his own session on 802.11s support > on mac80211 > > Luis Cheers Julie

1 0

about 64-bits division in kernel
by loody May 21, 2011

May 21, 2011

hi all: My platform is 32-bits cpu and I need following calculation in my driver. #define longdiv(sr1, sr2, div) (unsigned long )((((unsigned long long)(sr1) << 32) ^ (sr2)) / (div)) my question are: 1. why "__udivdi3" has any relationship with above calculation? 2. I know the above calculation is implemented in clibc, but why kernel still implement itself? why kernel try to make another wheel instead of including what clib provided ? -- Regards,

2 5

getting access to vlan tag on a non vlan interface
by Mihir Lala May 21, 2011

May 21, 2011

I'm receiving vlan tagged packets on a non-vlan interface and I want to be able to strip off the tag on the way in and later insert the tag back in on the way out. I've looked at two options but none of them work for me: - Hooking into netfilter's iptables hooks -- since I do not have a vlan interface, the packets do not even reach L3 and so my hooks won't even get invoked. - Hooking into netfilter's ebtables hooks, will give me access to the vlan tag, but then I am forced to create a bridge. I don't want to do that. Can anyone provide some insight as to how I can achieve this? thanks, nova

1 0