- kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Is `IS_ERR_VALUE` indicates that the return value is invalid?
by 乃宏周 Nov. 21, 2013

Nov. 21, 2013

In kernel source, `IS_ERR_VALUE` is defined: #define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO) It's usage can be realized literally, but definition is not. Can I use this macro to determines the kernel API's result is valid? Example: if (IS_ERR_VALUE(filp_open(device))) { filp_close(device); }

3 2

How to reorder the inbuilt driver loading in SLES 11 SP3 during OS boot
by san deep Nov. 20, 2013

Nov. 20, 2013

Hi, In SLES 11 SP3 32bit , is there any way we can reorder the inbuilt driver loading during OS boot. On boot, I want to load first my driver which I installed as rpm if my driver not claim the controller then then I want the inbuilt driver to load and claim the controller. As of now in built driver loads first and claiming controller. Made few changes by editing the initrd image like making init, run_all.sh and other shell scripts changes but no use. Can you please help me. Regards, Sandeep

1 0

Ordering / preemption of work in a workqueue preempt?
by Rajat Jain Nov. 19, 2013

Nov. 19, 2013

Hi, I have a single work queue, on which I have scheduled a worker function [using queue_work(wq, fn)] in interrupt context. I get the interrupt twice before the work queue gets a chance to run, and hence the same function will get queued twice (with different private context - arguments etc) which is fine and expected. Questions: 1) Is it possible that the instance that was queued by 2nd interrupt, can get to run BEFORE the instance that was queued by 1st interrupt? In other words, is reordering possible? 2) Is it possible that one running instance of the function, can get preempted by second instance of the same work queue? I read through http://lwn.net/Articles/511421/ and it talks about same work queue cannot run on different CPU, but I have doubt about single CPU. If If I am writing a worker function, does my code have to be ready that it can be preempted by another instance of the same function? Please note that I understand that my worker function can preempted by other processes, my doubts are related to the same workqueue. Thanks, Rajat

4 5

Embedded Toolchain
by Anand Moon Nov. 19, 2013

Nov. 19, 2013

Hi All, During compilation of openwrt it obviously create an embedded tookchain using the gcc, buildutils and the kernel for architecture i.e. (MIPS or ARM). So is it that this toolchain will work for that particular architecture board only and for that particular kernel. Can this new toolchain replace the old toolchain for embedded boards of same architecture i.e. MIPS or ARM. Please share your thoughts on this. -Anand Moon

2 2

Can mm_struct of a process be null?
by Paul Davies C Nov. 18, 2013

Nov. 18, 2013

Hi, I happen to find this code snippet in the kernel source : **/*struct mm_struct *mm=current->mm**;** ** /* some other code */ ** if(mm){ /*<==Why is **this here? */** ** /*read the contents by locking*/** ** } */The/if /checks whether the mm_struct of the current process is NULL or not. That means the mm_struct of a process can become NULL. How can that happen?

3 2

Querry related to exporting Symbols
by Vishwas Srivastava Nov. 16, 2013

Nov. 16, 2013

Hi, My question is, 1: can two modules export symbols to "each other". (exporting symbol and including .h file is sufficient??) 2: I am compiling a kernel module and exporting few symbols, which another kernel module (compiled with option obj-y ) will use. Is it possible first of all? what is the way to achieve this (exporting symbol and including .h file is sufficient??) thanks in advance, Vishwas Srivastava

2 1

Best practice to lock a read/write to a HW register
by Luca Ellero Nov. 15, 2013

Nov. 15, 2013

Hi all, can someone please show me which is the best practice to lock a read/write to a hardware register. In other words if, in a driver, I want to modify a bit in a HW register, I have to read the register, set/reset the relevant bit and write back the reg. But what can I do to be sure that no other code modifies the register between my read and write? Is spin_lock() suitable for this purpose? Thanks Best regards Luca

5 5

Linux Kernel - Modifying a module_param variable from other drivers
by manty kuma Nov. 15, 2013

Nov. 15, 2013

Dear all, I see that when we declare a variable as module_param from a driver, i can see it listed in "/sys/module/xxx/parameters/...". Ex : /sys/module/usbcore/parameters/autosuspend we can modify and read it with echo and cat commands from terminal. But is there a way i can read this value from other drivers? Common sense says it should be there because if we are able to access them from user space, from kernel space we should definitely be able to do. Is it so? If yes, what are the API's? Posted teh same on SO - http://stackoverflow.com/questions/19973866/linux-kernel-modifying-a-module… Reply either here or on SO. Regards, Sandeep

2 5

get mail
by BaiYingshan Nov. 15, 2013

Nov. 15, 2013

get

1 0

Are you interested in a Linux Kernel Off-topic Mailing List?
by Aldo Iljazi Nov. 14, 2013

Nov. 14, 2013

Hello everyone. I am thinking of creating a Mailing List for our community but for unofficial topics. I think it would help to know each other and it would expand our conversation into different areas. Politics and Religion are prohibited topics. I was thinking the areas of discussion to be more on Science, Sports, Life, Philosophy etc. What do you think? I also created a poll here: http://poll.fm/4hqba -- Aldo Iljazi

7 11