March 2016 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Re: Adding new protocol to linux.
by Manoj Nayak March 28, 2016

March 28, 2016

> 1) Is it possible to write a new protocol for linux with an out of > tree module without modifing socket.h file? I think this has been already tried in the following code. http://lxr.free-electrons.com/source/include/net/bluetooth/bluetooth.h#L36 http://lxr.free-electrons.com/source/include/linux/socket.h#L239 The challenge is to expose this development specific header file to userspace. The following document talks about that. http://kernelnewbies.org/KernelHeaders Regards Manoj Nayak

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Real-time audio over local network with good quality
by Ricardo Biehl March 28, 2016

March 28, 2016

Hello guys! Sorry if this question is not part of the scope of this list. I'm developing a real-time microphone system that will work over local network using ALSA library and sockets API with IP (UDP/TCP support) <https://github.com/ricardobiehl/ipmic>. The purpose is to make a good replacement to traditional microphone systems (wired or wireless). The problem is that I found difficulties in network control and in ALSA library too :-) . Basically I need help to select the best network scheduler algorithm, set the right parameters, and (in audio) create a PCM plug which supports (1 channel * 16 bit sample * 22050 Hz) and BLOCKING opening mode. All this without quality loss and real-time. Any contribution with the project is welcome! Thank you! -- Ricardo Biehl Pasquali

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Re: Real-time audio over local network with good quality
by Ricardo Biehl March 28, 2016

March 28, 2016

2016-03-27 23:27 GMT-03:00 Rohit Vashist <rohitvashist2kk3(a)gmail.com>: > Hello Ricardo, > > Hope you are good. > I would suggest you post the query on alsa dev list(mail forum) for more > specific reply on your queries on ALSA driver. Ok, thanks :-) I'll do it! > Also,i kind of like the idea.Are you looking for some assistance on your > project would love to contribute. Cool! As I've told, anyone is welcomed to contribute in the project, provided that it respects the original purpose and the KISS philosophy. > > I am working in an MNC in Audio Driver Domain for last 7 years. Wow! > > https://www.linkedin.com/profile/preview?locale=en_US&trk=prof-0-sb-preview… ^ this link didn't open :-( Cheers and thank you for reply! > > On Mon, Mar 28, 2016 at 12:48 AM, Ricardo Biehl <rbpoficial(a)gmail.com> > wrote: >> >> Hello guys! >> >> Sorry if this question is not part of the scope of this list. >> >> I'm developing a real-time microphone system that will work over local >> network using ALSA library and sockets API with IP (UDP/TCP support) >> <https://github.com/ricardobiehl/ipmic>. >> The purpose is to make a good replacement to traditional microphone >> systems (wired or wireless). >> The problem is that I found difficulties in network control and in >> ALSA library too :-) . >> Basically I need help to select the best network scheduler algorithm, >> set the right parameters, and (in audio) create a PCM plug which >> supports (1 channel * 16 bit sample * 22050 Hz) and BLOCKING opening >> mode. All this without quality loss and real-time. >> >> Any contribution with the project is welcome! >> >> Thank you! >> >> -- >> Ricardo Biehl Pasquali >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > > -- > Regards, > Rohit Vashist > > -- Ricardo Biehl Pasquali 2016-03-27 23:27 GMT-03:00 Rohit Vashist <rohitvashist2kk3(a)gmail.com>: > Hello Ricardo, > > Hope you are good. > I would suggest you post the query on alsa dev list(mail forum) for more > specific reply on your queries on ALSA driver. > Also,i kind of like the idea.Are you looking for some assistance on your > project would love to contribute. > > I am working in an MNC in Audio Driver Domain for last 7 years. > > https://www.linkedin.com/profile/preview?locale=en_US&trk=prof-0-sb-preview… > > On Mon, Mar 28, 2016 at 12:48 AM, Ricardo Biehl <rbpoficial(a)gmail.com> > wrote: >> >> Hello guys! >> >> Sorry if this question is not part of the scope of this list. >> >> I'm developing a real-time microphone system that will work over local >> network using ALSA library and sockets API with IP (UDP/TCP support) >> <https://github.com/ricardobiehl/ipmic>. >> The purpose is to make a good replacement to traditional microphone >> systems (wired or wireless). >> The problem is that I found difficulties in network control and in >> ALSA library too :-) . >> Basically I need help to select the best network scheduler algorithm, >> set the right parameters, and (in audio) create a PCM plug which >> supports (1 channel * 16 bit sample * 22050 Hz) and BLOCKING opening >> mode. All this without quality loss and real-time. >> >> Any contribution with the project is welcome! >> >> Thank you! >> >> -- >> Ricardo Biehl Pasquali >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > > -- > Regards, > Rohit Vashist > > -- Ricardo Biehl Pasquali

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unregister_input_polled_device() leads to null pointer deref
by Okash Khawaja March 28, 2016

March 28, 2016

Hi, I'm writing a i2c device driver. In probe(), among other things I call: polled_input = input_allocate_polled_device(); input_register_polled_device(polled_input); Then inside remove(), I extract the instance of input_polled_dev and call input_unregister_polled_device(polled_input); This results in kernel error: "Unable to handle kernel NULL pointer dereference at virtual address 00000474". It turns out that the input_dev pointer inside input_polled_dev is null which leads to this error. But why is input_dev pointer null? It is not null inside probe() function and I don't release it anywhere. This is code: http://pastebin.com/JJdepyEG and here is link to the output, along with my log statements: http://pastebin.com/badwSvyy. Thanks, Okash

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Re: Adding new protocol to linux
by Manoj Nayak March 28, 2016

March 28, 2016

> 2) Could netlink socket be used to solve this? .. and Netlink is used to transfer information between kernel and user-space processes. It consists of a standard sockets-based interface for user space processes and an internal kernel API for kernel modules. netlink socket does not call dev_queue_xmit(). But here the requirement is to transfer the packet using Nordic's nRF24L01+. AF_PACKET is used to output a raw packet from userspace to a device layer. Even AF_PACKET does that using proto_ops and net_proto_family. Regards Manoj Nayak

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Attach my own pid
by Nitin Varyani March 27, 2016

March 27, 2016

Hi, The linux kernel attaches a pid to newly forked process. I want to create a facility by which a process has the option of attaching a new pid to its child which is not in the pid space. Any suggestions of how this can be achieved? Nitin

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Adding new protocol to linux.
by Daniel. March 26, 2016

March 26, 2016

Hi everybody, I'm planing to write a socket API for Nordic's nRF24L01+ and I was digging on socket code and find all supported protocols at include/linux/socket.h with all that #define AF_x y. So my questions are: 1) Is it possible to write a new protocol for linux with an out of tree module without modifing socket.h file? 2) Could netlink socket be used to solve this? .. and 3) I saw that there is net_device_ops and proto_ops. How they are tied together? Thanks in advance and Best regards, -- "Do or do not. There is no try" Yoda Master

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Re: Adding new protocol to linux.
by Daniel March 26, 2016

March 26, 2016

Thanks Rami, it helps a lot. I'm using SocketCAN as reference for doing this, and I see AF_CAN at socket.h. I saw that protocol family create is called by __sock_create(). Also found that proto_ops bind is used (in the example of the CAN) to find the interface where the communication realy happens.. I am wondering if is possible to achieve my goal with and only with out of tree module. I'm planing to get this merged at main tree anyway, but first I would like to keep it out ou tree until is ready... Cheers, 2016-03-26 8:04 GMT-03:00 Rami Rosen <roszenrami(a)gmail.com>: > Hi Daniel, > > Following are answers for several of your questions: > Adding a protocol in Linux is done first by defining a protocol, and > then registering it with the proto_register() method: > http://lxr.free-electrons.com/source/net/core/sock.c#L2815 > For that you need to define a proto object; for TCPv4 it is done thus, > for example: > http://lxr.free-electrons.com/source/net/ipv4/tcp_ipv4.c#L2315 > > Defining a protocol is not enough, you should also register a protocol > handler for this protocol. > Defining a protocol handler is done first by > defining a packet_type object > of this protocol and then defining a callback for this packet_type. > So for example, for IPv4, a packet_type object called ip_packet_type is > defined in http://lxr.free-electrons.com/source/net/ipv4/af_inet.c#L1677 > > The protocol handler for this packet type is ip_rcv(): > http://lxr.free-electrons.com/source/net/ipv4/ip_input.c#L378 > > This protocol is registered with dev_add_pack(): > http://lxr.free-electrons.com/source/net/core/dev.c#L397 > > So, for example, for IPv4 it is done in inet_init(): > http://lxr.free-electrons.com/source/net/ipv4/af_inet.c#L1791 > > Apart from the protocol handler, a unique Ethernet type should be > defined for this protocol; for IPv4 we have 0x0800 (ETH_P_IP) > http://lxr.free-electrons.com/source/include/uapi/linux/if_ether.h#L46 > and for the ARP protocol we have 0x0806 (ETH_P_ARP), and so on. > > The Ethernet type in the Ethernet header represents the protocol > assigned to this packet. > > The net_device_ops structure is not related, it merely represents the > interface of the of the kernel representation of network device (a > net_device object) to userspace, for userspace operations like > setting the MTU, setting the MAC address, bringing the device up and > down, putting the device in promiscuous mode, and more. > > Hope this helps! > > Regards, > Rami Rosen > http://ramirose.wix.com/ramirosen > > > On 26 March 2016 at 05:00, Daniel. <danielhilst(a)gmail.com> wrote: >> Hi everybody, >> >> I'm planing to write a socket API for Nordic's nRF24L01+ and I was >> digging on socket code and find all supported protocols at >> include/linux/socket.h with all that #define AF_x y. So my questions >> are: >> >> 1) Is it possible to write a new protocol for linux with an out of >> tree module without modifing socket.h file? >> 2) Could netlink socket be used to solve this? .. and >> 3) I saw that there is net_device_ops and proto_ops. How they are tied together? >> >> Thanks in advance and >> Best regards, >> >> -- >> "Do or do not. There is no try" >> Yoda Master >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies -- "Do or do not. There is no try" Yoda Master

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Re: Contiguous memory allocator
by Manoj Nayak March 26, 2016

March 26, 2016

cma_declare_contiguous() allocates memory from memblock. cma_init_reserved_mem() initialize the memory. Then the memory is given to buddy allocator with migration type MIGRATE_MOVABLE. when CMA needs those pages, it can take it from buddy allocator. We are supposed to use equivalent DMA api dma_declare_contiguous(). dma_declare_contiguous() calls cma_declare_contiguous(). http://lxr.free-electrons.com/source/arch/arm/mach-davinci/devices-da8xx.c#… Regards Manoj Nayak

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HC-SRO4 ultrasonic distance driver
by Johannes Thoma March 24, 2016

March 24, 2016

Hi all, I wrote a driver for the popular HC-SRO4 ultrasonic distance sensor. It is beta and has been tested on the Raspberry PI by me and my brother: here is the stand-alone repo: https://github.com/johannesthoma/linux-hc-sro4 I would like to contribute it to the linux kernel, however I am a little bit nervous reading through the Documentation/Submitting[Patches][Drivers] documentation (in particular the How to piss off a kernel developer sections ;), so I wanted to ask if I could post the patch (it will be against the char/mics device kernel tree at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git , I think this is the correct location) on this list first, maybe someone can tell me if the formatting and the driver are correct.. I also have some driver specific questions: *) First, does it really belong to drivers/misc ? There are other sensors there as well, so I suppose this location is right. *) As of now, I've created a new device class "distance" where the sysfs control files live in (so the configuration file is /sys/class/distance/configure ), it works for me (tm) but I don't know if code that creates new device classes would be accepted. Is there another solution to put the control files in? Maybe under /sys/class/gpio? *) I've filled out the parent device field in device_create_with_groups() to NULL, I'm not sure if this is right. If I put a parent, should it be the GPIO device (the HC_SRO4 is attached to two GPIO pins)? *) When I submit the patch, I've read that one should cc the maintainers (that would be Arnd Bergmann <arnd(a)arndb.de> and Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>) but on what list should I post the patch at all? Is it lkml.org? Please let me know if it ok to post the patch to this list first. Thanks a lot, - Johannes

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