October 2014 - kernelnewbies@kernelnewbies.org

Implementing a driver that listen to a GPIO
by Luca Ellero Oct. 2, 2014

Oct. 2, 2014

Hi, I'm working on an ARM platform running Linux kernel 2.6.35. The board is powered by a "micro UPS" that guarantees about 500 ms of "self-power" in case of a power failure. Power failure is reported by a GPIO that can raise an interrupt when power is falling. I would like to implement a mechanism which listen to the GPIO and when power is going down it saves some amount of data (about 100 KB) and then shutdown the board. Which is best way to do that? I'm thinking about 3 ways of doing that: 1) |using |theusermode-helper API: Implement a driver which use c|all_usermodehelpe|rto launch an user space app 2) Using a gpio-event driver, as explained here: http://wiki.gumstix.org/index.php?title=GPIO_Event_Driver#Detecting_events 3) Implement my own driver using completions. Something like this: DECLARE_COMPLETION(comp); interrupt_handler(){ complete(comp); } ups_read (){ wait_for_completion(&comp); copy_to_user(...something...); return 0; /* EOF */ } static const struct file_operations ups_driver_ops = { .owner = THIS_MODULE, .read = ups_read, }; static struct miscdevice hello_miscdev = { .minor = MISC_DYNAMIC_MINOR, .name = "ups", .fops = &ups_driver_ops }; init (){ request_irq(interrupt_handler); misc_register(&hello_miscdev); } and in userspace a process which execute a read from /dev/ups. When the call to readreturns, it means that power is falling. What do you think? Any suggestion is welcome. Thanks Regards Luca Ellero

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Suspend resume times.
by jocke＠holstenhof.se Oct. 2, 2014

Oct. 2, 2014

Hi! This may be a stupid question, but is there an existing system available to actually monitor how long time a suspend/resume cycle takes and which drivers consume the most time? BRs, Joachim Holst

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Need to enable 2 MPP in dtsi file...
by siva sangeetha Oct. 1, 2014

Oct. 1, 2014

Hi, I am facing one issue, actually my requirement is i should enable 2 MPP, MPP4 & MPP6 in one node. how to achieve this?

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Linux kernel Network Programing
by Mohit Varma Oct. 1, 2014

Oct. 1, 2014

Hello, I know this is a Kernel newbie list , however, this question is directed more towards programmers who have been here for quite a while. I want to venture into linux network programming, ipv6, router programming, network drivers, programming network security products etc on the kernel side not on the user side. I know a book ...linux kernel network programming which will help me get started. Are there any more books which can help me. Secondly, how to look for problems to work on...more importantly how to ensure that hardware dependency doesn't come in my way...is there a simulated environment that I can use. Thanks Mohit

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Alsa Driver - sound from gpio
by Raphael Philipe Oct. 1, 2014

Oct. 1, 2014

Hi! I'm a newbie on ALSA architecture. I would like to known if it would be possible to create a sound driver for a a PCM sound beeing acquired by the GPIO of a processor, like the ARM of a Beaglebone Black. Beaglebone has more than 32 bits of gpio so I intend to acquire the audio signal through a A/D CI (sigma delta) connected to a FPGA that would provide it to the Beaglebone Black in parallel form (PCM code), through the GPIO. Is that possible? Regards

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MPI_WSIZE()
by Dave Tian Oct. 1, 2014

Oct. 1, 2014

Hi, Can someone point me to the implementation of MPI_WSIZE()? I assume it should be some old macro under <linux/mpi.h>. However, I am not able to find it within <linux/crypto/mpi.h> under RH kernel 2.6.32-358 or in the latest 3.x kernel. Thanks, Dave

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