March 2015 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Kernel Locking Question
by Nicholas Krause March 12, 2015

March 12, 2015

Greetings All, After learning about kernel locking and how atomic operations are good in terms of improving CPU scalability in terms of making a critical region much smaller. I was wondering of how this would improve file system scalability and reliability if implemented in file system code for btrfs worker threads. Nick -- Sent from my Android device with K-9 Mail. Please excuse my brevity.

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Kernel preemption
by Rock Lee March 12, 2015

March 12, 2015

Hi, guys: I have a device with only one CPU. I am wondering whether there will be only one task running on CPU and this task will not be interrupted by scheduler if I make the kernel non-preemptive ? At this situation, whether the time splice will not exist? Regards --- Rock Lee

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confusing code....whats the point of this construct ?
by Nicholas Mc Guire March 11, 2015

March 11, 2015

HI ! Trying to understand the intent of this code construct drivers/net/wireless/ath/ath10k/mac.c:ath10k_flush() <snip> ret = wait_event_timeout(ar->htt.empty_tx_wq, ({ bool empty; spin_lock_bh(&ar->htt.tx_lock); empty = (ar->htt.num_pending_tx == 0); spin_unlock_bh(&ar->htt.tx_lock); skip = (ar->state == ATH10K_STATE_WEDGED) || test_bit(ATH10K_FLAG_CRASH_FLUSH, &ar->dev_flags); (empty || skip); }), ATH10K_FLUSH_TIMEOUT_HZ); <snip> FYI include/linux/wait.h:wait_event_timeout() <snip> * wait_event_timeout - sleep until a condition gets true or a timeout elapses * @wq: the waitqueue to wait on * @condition: a C expression for the event to wait for * @timeout: timeout, in jiffies <snip> So the wait_event_timeout condition here ends up being (empty || skip) but what is the point of puting this code into the parameter list of wait_event_timeout() ? Would it not be equivalent to: bool empty; ... spin_lock_bh(&ar->htt.tx_lock); empty = (ar->htt.num_pending_tx == 0); spin_unlock_bh(&ar->htt.tx_lock); skip = (ar->state == ATH10K_STATE_WEDGED) || test_bit(ATH10K_FLAG_CRASH_FLUSH, &ar->dev_flags); ret = wait_event_timeout(ar->htt.empty_tx_wq, (empty || skip), ATH10K_FLUSH_TIMEOUT_HZ); What am I missing here ? thx! hofrat

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Difference between System.map and /proc/kallsyms
by Jamal March 10, 2015

March 10, 2015

Hi.. After reading Documentation on System.map, i understood that , whenever an oops happens the following addresses will be converted to its function name by klogd daemon using System.map. Now when we have /proc/kallsyms which stores the symbol table in the kernel image itself.Then what is the need of System.map file??Is any process or daemon still using it?? Regards, Md.Jamal

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Get local CPU id
by Matwey V. Kornilov March 9, 2015

March 9, 2015

Hi, I would like to somehow obtain local CPU core ID in the interrupt handler function. I want to see how my interruptions are distributed among different CPU cores under different conditions. How should I do that?

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Raw binary Image of linux
by chirag garg March 9, 2015

March 9, 2015

Hi all, I am new to the linux kernel source code. I want to compile linux source code for imx6 ARM based platform. I want to generate raw binary image (.bin file) and .dtb file. Can any one help me in this.? Thanks in advance Regards Chirag Garg IIT Madras , Rise Lab

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How to generate a kernel source tree with macros expanded？
by Tao Jiang (姜涛) March 9, 2015

March 9, 2015

Hi: After make menuconfig, is there a way to generate a kernel source tree with macros expanded? It's too complicate for me to find out wether a macro is defined or not, or which value is used for a macro. Thanks for advance. -- Tao Jiang (姜涛)

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getting interrupt number
by Ronit Halder March 9, 2015

March 9, 2015

How to get the interrupt number of a device.I know it's device id and the bus number. The device is a usb mouse.

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Re: Mouse driver
by nick March 9, 2015

March 9, 2015

On 2015-03-06 11:36 PM, Ronit Halder wrote: > This is my semester project and Thanks. > Does it have to be a input driver? If you really want to impress your teacher and get a better mark,try writing a basic network or usb driver. Nick > On Sat, Mar 7, 2015 at 10:04 AM, nick <xerofoify(a)gmail.com> wrote: >> Ronit, >> What are your reasons for writing this driver? In addition if you have >> the kernel tree lying around look under drivers/input/mouse for mouse >> drivers that are in production to help you understand how to write >> one better. >> Good Luck, >> Nick >> >> On 2015-03-06 11:27 PM, Ronit Halder wrote: >>> Hi,I want to write mouse driver for linux ( usb mouse). I am reading >>> "Linux device driver" and "Linux kernel development". But i don't how >>> to start writing the driver. >>> So,Please help. >>> >>> Best regards, >>> Ronit. >>> >>> _______________________________________________ >>> Kernelnewbies mailing list >>> Kernelnewbies(a)kernelnewbies.org >>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>>

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Documentation/Test application to test the HID I2C sensorhub
by s.rawat March 7, 2015

March 7, 2015

Where can i get the documentation/test app to test the HID over I2C devices.- Sensorhub,custom devices,mice. iIn the kernel documentation there is an application generic_buffer but I think it is only for reading the input reports.I want to send custom reports to Sensorhub over HID I2C and get their response. There is HIDAPIs <http://www.signal11.us/oss/hidapi/> for USB HID though. Many thanks, Rgds, Saurabh

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