March 2013 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Reading the framebuffer area.
by manty kuma March 7, 2013

March 7, 2013

Hi everyone, Request you to kindly go through the question posted here on SO: http://stackoverflow.com/questions/15264188/reading-the-protected-framebuff… *Reason why i am asking here :* Because i think this has got to do with linux display drivers.. or some kernel changes..

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RE:Query on skb buffer (Kumar amit mehta)
by Pranay Kumar Srivastava March 7, 2013

March 7, 2013

> -----Original Message----- > From: kernelnewbies-bounces(a)kernelnewbies.org [mailto:kernelnewbies- > bounces(a)kernelnewbies.org] On Behalf Of kernelnewbies- > request(a)kernelnewbies.org > Sent: Thursday, March 07, 2013 8:52 AM > To: kernelnewbies(a)kernelnewbies.org > Subject: Kernelnewbies Digest, Vol 28, Issue 12 > > Send Kernelnewbies mailing list submissions to > kernelnewbies(a)kernelnewbies.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > or, via email, send a message with subject or body 'help' to > kernelnewbies-request(a)kernelnewbies.org > > You can reach the person managing the list at > kernelnewbies-owner(a)kernelnewbies.org > > When replying, please edit your Subject line so it is more specific than "Re: > Contents of Kernelnewbies digest..." > > > Today's Topics: > > 1. Query on skb buffer (Kumar amit mehta) > 2. Re: Query on skb buffer (Valdis.Kletnieks(a)vt.edu) > 3. Several unrelated beginner questions. (Konstantin Kowalski) > 4. Re: Several unrelated beginner questions. (Gaurav Jain) > 5. Re: Several unrelated beginner questions. > (Valdis.Kletnieks(a)vt.edu) > 6. zap_low_mappings (ishare) > 7. Re: zap_low_mappings (Valdis.Kletnieks(a)vt.edu) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 6 Mar 2013 10:39:13 -0800 > From: Kumar amit mehta <gmate.amit(a)gmail.com> > Subject: Query on skb buffer > To: kernelnewbies(a)kernelnewbies.org > Message-ID: <20130306183913.GA3328(a)gmail.com> > Content-Type: text/plain; charset=us-ascii > > My current understanding is that the skb, while being passed along various > layers in linux network stack, will be manipulated majorly, using the > skb->{head|data|tail|end|len} fields. > > Suppose that my application (say 'ping') sends a ICMP echo request with a > large packet size of 4k, i.e. $ ping -s 4096 <dest addr> Now, if alloc_skb(4096, > GFP_KERNEL) is the routine that gets called to allocate the kernel buffer > then, how does the kernel manages such prospective memory allocation > failures and how kernel manages large packet requests from the application. > > -Amit [Pranay Kumar Srivastava] Perhaps you should've a look at linear and non-linear data (skb_frags to be specific). That's how large data is handled however I don't think you'll be doing that with ICMP or UDP. Reading directly from skbuffs for UDP would also give you header information however with TCP it doesn't. So unless there's any need for it perhaps it can be done in userland or use sock_sendmsg or sendfile (for zero copy). --P.K.S > > > > ------------------------------ > > Message: 2 > Date: Wed, 06 Mar 2013 14:32:27 -0500 > From: Valdis.Kletnieks(a)vt.edu > Subject: Re: Query on skb buffer > To: Kumar amit mehta <gmate.amit(a)gmail.com> > Cc: kernelnewbies(a)kernelnewbies.org > Message-ID: <9932.1362598347(a)turing-police.cc.vt.edu> > Content-Type: text/plain; charset="us-ascii" > > On Wed, 06 Mar 2013 10:39:13 -0800, Kumar amit mehta said: > > > Now, if alloc_skb(4096, GFP_KERNEL) is the routine that gets called to > > allocate the kernel buffer then, how does the kernel manages such > > prospective memory allocation failures and how kernel manages large > > packet requests from the application. > > Did you actually look at the source for use of alloc_skb() and how it handles > error returns? > > (Hint - the kernel doesn't do the same thing at every use of alloc_skb(), > because an allocation failure needs to be handled differently depending on > where it happens. At some places, just bailing out and dropping the packet > on the floor without any notification to anybody is appropriate. At other > places, we need to propagate an error condition to the caller). > > Typical pattern (from net/core/sock.c:) > > /* > * Allocate a skb from the socket's send buffer. > */ > struct sk_buff *sock_wmalloc(struct sock *sk, unsigned long size, int force, > gfp_t priority) { > if (force || atomic_read(&sk->sk_wmem_alloc) < sk->sk_sndbuf) { > struct sk_buff *skb = alloc_skb(size, priority); > if (skb) { > skb_set_owner_w(skb, sk); > return skb; > } > } > return NULL; > } > EXPORT_SYMBOL(sock_wmalloc); > > and then the caller does something like this (net/ipv4/ip_output.c, in > function __ip_append_data(): > > } else { > skb = NULL; > if (atomic_read(&sk->sk_wmem_alloc) <= > 2 * sk->sk_sndbuf) > skb = sock_wmalloc(sk, > alloclen + hh_len + 15, 1, > sk->sk_allocation); > if (unlikely(skb == NULL)) > err = -ENOBUFS; > else > /* only the initial fragment is > time stamped */ > cork->tx_flags = 0; > } > if (skb == NULL) > goto error; > > >

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Query on skb buffer
by Kumar amit mehta March 6, 2013

March 6, 2013

My current understanding is that the skb, while being passed along various layers in linux network stack, will be manipulated majorly, using the skb->{head|data|tail|end|len} fields. Suppose that my application (say 'ping') sends a ICMP echo request with a large packet size of 4k, i.e. $ ping -s 4096 <dest addr> Now, if alloc_skb(4096, GFP_KERNEL) is the routine that gets called to allocate the kernel buffer then, how does the kernel manages such prospective memory allocation failures and how kernel manages large packet requests from the application. -Amit

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Creation Of New Partition in EMMC
by Ranganath T.M March 6, 2013

March 6, 2013

Hi All, I am trying to create new partition (p7) in emmc, presently I am having 6 partition in emmc(p1 to p6). I am not able to get some pointers can any one help me. And also I tried to give new partition in uboot_envparameters_android.cfg i,e by adding another size and offset in it. But it fails, kindly help to get it. Below are the emmc partition uboot arguments in uboot_envparameters_android.cfg, emmcargs=setenv bootargs ${bootargs} root=/dev/ram0 rw initrd=${initrd},${initrdsize} blkdevparts=mmcblk0:16384@147456 ,688128@163840,2048@1501184,262144@851968,385024@1114112,8@81912 ,700000@1503232 rootwait Thanks and Regards, Ranganath.T.M

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Regarding GPIO driver module
by Rajesh Bhaskaran March 6, 2013

March 6, 2013

Hi all , I was trying to write a GPIO driver module for Hawkboard , in order to toggle the LEDs connected to the GPIOs . I am using a OMAP L138 processor , and am trying to do a ioremap of the physical address space to the Kernel's virtual address space . But I guess I am not able to figure out the exact base address of the GPIO bank . I am basically trying to toggle the GPIO Bank 6 . I went through the OMAP L138 reference manual , but am unable to find the base address . Afterwards I plan to use the ioctl function to toggle the LEDs . Attaching herewith the link to the OMAP L138 reference manual . Reference manual : www.ti.com/lit/ug/spruh77a/spruh77a.pdf Could anyone kindly guide me , on the procedure to decipher the Baseaddress of the GPIO Bank 6 from the Reference manual ? Thanks in advance ! Cheers , ~RCB~

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RE: Major/minor numbers
by Pranay Kumar Srivastava March 6, 2013

March 6, 2013

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RE: Major/minor numbers
by Pranay Kumar Srivastava March 6, 2013

March 6, 2013

> -----Original Message----- > From: kernelnewbies-bounces(a)kernelnewbies.org [mailto:kernelnewbies- > bounces(a)kernelnewbies.org] On Behalf Of kernelnewbies- > request(a)kernelnewbies.org > Sent: Tuesday, March 05, 2013 5:53 PM > To: kernelnewbies(a)kernelnewbies.org > Subject: Kernelnewbies Digest, Vol 28, Issue 9 > > Send Kernelnewbies mailing list submissions to > kernelnewbies(a)kernelnewbies.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > or, via email, send a message with subject or body 'help' to > kernelnewbies-request(a)kernelnewbies.org > > You can reach the person managing the list at > kernelnewbies-owner(a)kernelnewbies.org > > When replying, please edit your Subject line so it is more specific than "Re: > Contents of Kernelnewbies digest..." > > > Today's Topics: > > 1. Module compilation error (Pietro Paolini) > 2. Re: Module compilation error (Mulyadi Santosa) > 3. Re: Module compilation error (Valdis.Kletnieks(a)vt.edu) > 4. pthread_lock (ishare) > 5. Re: pthread_lock (Mandeep Sandhu) > 6. Re: pthread_lock (Valdis.Kletnieks(a)vt.edu) > 7. Major/minor numbers (Shraddha Kamat) > 8. Re: pthread_lock (Mandeep Sandhu) > 9. Re: pthread_lock (ishare) > 10. Re: Major/minor numbers (Anuz Pratap Singh Tomar) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Mon, 4 Mar 2013 19:48:33 -0500 (EST) > From: Pietro Paolini <pulsarpietro(a)aol.com> > Subject: Module compilation error > To: kernelnewbies(a)kernelnewbies.org > Message-ID: <8CFE7524C1296F0-1764-9EDF@webmail- > m235.sysops.aol.com> > Content-Type: text/plain; charset="us-ascii"; format=flowed > > Hi all, > > I tried, as beginner, to compile a simple module downloaded by internet, > hello_printk, I am using ArchLinux and I followed the simplest way for > compile a new kernel tree from here : > > https://wiki.archlinux.org/index.php/Kernels/Compilation/Arch_Build_Syste > m > > But when I try to compile I catch these errors: > > echo >&2 " ERROR: Kernel configuration is invalid."; \ > echo >&2 " include/generated/autoconf.h or > include/config/auto.conf are missing.";\ > echo >&2 " Run 'make oldconfig && make prepare' on kernel src > to fix it."; \ > echo >&2 ; \ > /bin/false) > > Of course I checked the path of the kernel and under the directory wrote on > the error messages I can find the files autoconf.h and auto.conf that I really > don't understand what could be wrong, the makefile is really really simple > then I can post it: > > obj-m := hello_printk.o > KDIR ?= mypersonalpath/core/linux/src/linux-3.7 > PWD := $(shell pwd) > default: > $(MAKE) -C $(KDIR) M=$(PWD) modules > > Someone can help me ? > > > > Pietro Paolini > pulsarpietro(a)aol.com > > > > ------------------------------ > > Message: 2 > Date: Tue, 5 Mar 2013 09:07:51 +0700 > From: Mulyadi Santosa <mulyadi.santosa(a)gmail.com> > Subject: Re: Module compilation error > To: Pietro Paolini <pulsarpietro(a)aol.com> > Cc: kernelnewbies(a)kernelnewbies.org > Message-ID: > <CAGdaadZ=eziBhY6zTFzSC5PZ_yTzgnVjQ0rgbk_SQQCjyt6ZBA@mail. > gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > On Tue, Mar 5, 2013 at 7:48 AM, Pietro Paolini <pulsarpietro(a)aol.com> > wrote: > > Hi all, > > > > I tried, as beginner, to compile a simple module downloaded by > > internet, hello_printk, I am using ArchLinux and I followed the > > simplest way for compile a new kernel tree from here : > > > > https://wiki.archlinux.org/index.php/Kernels/Compilation/Arch_Build_Sy > > stem > > > > But when I try to compile I catch these errors: > > > > echo >&2 " ERROR: Kernel configuration is invalid."; \ > > echo >&2 " include/generated/autoconf.h or > > include/config/auto.conf are missing.";\ > > echo >&2 " Run 'make oldconfig && make prepare' on kernel src > > try the suggested above step. IIRC, those commands will do things like > preparing the neccessary object files, headers and so on, so it is ready for > you to be used on your kernel programming. > > Apologize since I can't provide deeper details about this. > > > > -- > regards, > > Mulyadi Santosa > Freelance Linux trainer and consultant > > blog: the-hydra.blogspot.com > training: mulyaditraining.blogspot.com > > > > ------------------------------ > > Message: 3 > Date: Mon, 04 Mar 2013 21:47:46 -0500 > From: Valdis.Kletnieks(a)vt.edu > Subject: Re: Module compilation error > To: Mulyadi Santosa <mulyadi.santosa(a)gmail.com> > Cc: Pietro Paolini <pulsarpietro(a)aol.com>, > kernelnewbies(a)kernelnewbies.org > Message-ID: <6607.1362451666(a)turing-police.cc.vt.edu> > Content-Type: text/plain; charset="us-ascii" > > On Tue, 05 Mar 2013 09:07:51 +0700, Mulyadi Santosa said: > > On Tue, Mar 5, 2013 at 7:48 AM, Pietro Paolini <pulsarpietro(a)aol.com> > wrote: > > > > echo >&2 " Run 'make oldconfig && make prepare' on kernel src > > > > try the suggested above step. IIRC, those commands will do things like > > preparing the neccessary object files, headers and so on, so it is > > ready for you to be used on your kernel programming. > > In addition, note that 'make oldconfig' followed by 'make prepare' will only > do the right thing and result in a usable module if the source tree matches > your running kernel. Doing 'make prepare' on a 3.7.2 source tree and then > building a module against it will result in a module that loads in a 3.7.2 kernel > with the same .config - but a different .config and/or release will have > anything from a module that simply won't load to one that blows up the > system for mysterious reasons. > > It's *highly* recommended that you first learn how to build, install, and boot > a self-compiled kernel (and remember to keep your distro kernel around), > and then once you got that down, *then* start building external modules > against it. >

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Some Links for Easy Understanding of Linux of Kernel Source code
by praveen kumar March 5, 2013

March 5, 2013

Hello all I am a collage student and i need some link so to under stand kernel source code easily and also how to do IPC programming thank you

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Major/minor numbers
by Shraddha Kamat March 5, 2013

March 5, 2013

Does the max number of devices supported by Linux limited by major minor number ? Can you please give me some pointers regarding this. -- Shraddha

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Module compilation error
by Pietro Paolini March 5, 2013

March 5, 2013

Hi all, I tried, as beginner, to compile a simple module downloaded by internet, hello_printk, I am using ArchLinux and I followed the simplest way for compile a new kernel tree from here : https://wiki.archlinux.org/index.php/Kernels/Compilation/Arch_Build_System But when I try to compile I catch these errors: echo >&2 " ERROR: Kernel configuration is invalid."; \ echo >&2 " include/generated/autoconf.h or include/config/auto.conf are missing.";\ echo >&2 " Run 'make oldconfig && make prepare' on kernel src to fix it."; \ echo >&2 ; \ /bin/false) Of course I checked the path of the kernel and under the directory wrote on the error messages I can find the files autoconf.h and auto.conf that I really don't understand what could be wrong, the makefile is really really simple then I can post it: obj-m := hello_printk.o KDIR ?= mypersonalpath/core/linux/src/linux-3.7 PWD := $(shell pwd) default: $(MAKE) -C $(KDIR) M=$(PWD) modules Someone can help me ? Pietro Paolini pulsarpietro(a)aol.com

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