October 2018 - kernelnewbies@kernelnewbies.org

What is "#define alloc_ieee80211 alloc_ieee80211_rsl"?
by John Whitmore Oct. 9, 2018

Oct. 9, 2018

Sorry I know what a #define is doing, but in this case I've no idea why it's used and what it's trying to achieve. This is from the rtl8192u driver in staging, where the alloc function (alloc_ieee80211) which is called by the probe function (rtl8192_usb_probe). So that's all good but a quick grep through the code and in the file drivers/staging/rtl8192u/ieee80211/ieee80211.h there's a line which defines that function as another function '_rsl' which don't exist anywhere in Kernel. #define alloc_ieee80211 alloc_ieee80211_rsl So what am I missing or why are a number of functions being redefined as another name, which doesn't exist? I'm tempted to remove any that don't exist but I should really find out what it is the lines are doing.

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How to make linux stop all processes/activities except the one I am benchmarking?
by Lev Olshvang Oct. 8, 2018

Oct. 8, 2018

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Diploma project with the Linux kernel
by Boian Karatotev Oct. 5, 2018

Oct. 5, 2018

Hello, I am a Computer Science student and for my last year I need to make and present a 'diploma project' at the end of June. So far I want to make a kernel module, whose description is in the following paragraph. I feel comfortable with C and my OS knowledge is maybe slightly better than my OS course. My question is: Would it possible to pull this off? I have no experience with the kernel and I want to get into kernel development, so this would be a perfect opportunity for that. My only issue is that this may be too complex for my experience. My idea: Something along the lines of checkpoint-restart as a kernel module. I want to ultimately be able to migrate a running process to a different machine (assuming same at least some basic similarity). I know of BLCR <http://crd.lbl.gov/departments/computer-science/CLaSS/research/BLCR/> and I am planning on using it as a guide, although I am unsure about working on it directly. As far as I know, the grading process does not require this to be 100% complete, so I am aiming at transferring at least all the memory, restoring file descriptors and maybe child processes/threads. I will really appreciate any feedback! Cheers, Boyan

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How to enable max98357a in sound/soc/codecs
by Paul Nader Oct. 4, 2018

Oct. 4, 2018

Hi, I'm trying to enable the max98357a codec in sound/soc/codecs. In the Kconfig file it is listed with an empty tristate so it doesn't show up when I do a make menu config. The only way I found so far was to patch the Kconfig and add a description to the tristate. It then appears in the menu when doing make menuconfig and it is also enabled if i patch my board's defconfig and add CONFIG_SND_SOC_MAX98357A=m to it. If I don't add a description then adding CONFIG_SND_SOC_MAX98357A=m doesn't enable it. How can I enable it without adding a description to the tristate? Thanks

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Forum registration activation broken?
by Paul Nader Oct. 4, 2018

Oct. 4, 2018

Hi, I registered to the forum this morning but it never sends any activation emails, maybe an admin could look into it? cheers

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style guide recommendations when including UAPI files?
by rpjday＠crashcourse.ca Oct. 3, 2018

Oct. 3, 2018

is there a strong (or even weak) style recommendation when including kernel header files under include/uapi in terms of explicitly including the "uapi" path component? i'm fully aware of the standard that most kernel code should include the "standard" kernel headers, such as: #include <linux/mii.h> where those headers are, of course, free to turn around and include the corresponding UAPI content; the above header file does indeed do just that: #include <linux/if.h> #include <uapi/linux/mii.h> however, in that very example, you can see the include of "linux/if.h" where there is, in fact, no header file include/linux/if.h, only include/uapi/linux/if.h. i can see from the top-level Makefile that that include will eventually pick up the UAPI version of the if.h header file: # Use USERINCLUDE when you must reference the UAPI directories only. USERINCLUDE := \ -I$(srctree)/arch/$(SRCARCH)/include/uapi \ -I$(objtree)/arch/$(SRCARCH)/include/generated/uapi \ -I$(srctree)/include/uapi \ -I$(objtree)/include/generated/uapi \ -include $(srctree)/include/linux/kconfig.h # Use LINUXINCLUDE when you must reference the include/ directory. # Needed to be compatible with the O= option LINUXINCLUDE := \ -I$(srctree)/arch/$(SRCARCH)/include \ -I$(objtree)/arch/$(SRCARCH)/include/generated \ $(if $(KBUILD_SRC), -I$(srctree)/include) \ -I$(objtree)/include \ $(USERINCLUDE) the point is, is that acceptable style? when i'm perusing kernel code and i see a reference to a header file <linux/if.h>, i simply assume it's a standard header file under include/, and i expect header files under the UAPI directory will explicitly say so in the include directive. thoughts? rday

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stack pointer used in vector_swi() in arm linux system call
by Anonymous Page Oct. 2, 2018

Oct. 2, 2018

Hi, While reading the vector_swi() routine for arm linux system call, I found that r0-r12 registers are copied to the kernel stack(below is the code). ENTRY(vector_swi) #ifdef CONFIG_CPU_V7M v7m_exception_entry #else sub sp, sp, #S_FRAME_SIZE stmia sp, {r0 - r12} @ Calling r0 - r12 As per my understanding, during system call arm enters into svc mode and jumps to vector_swi()routine and begins execution. The sp register of svc mode(sp_svc)points to kernel stack. r0-r12 registers are copied to the kernel stack. My question is how is the sp (sp_svc) register setup? How does it know the address of kernel stack? Is this kernel stack same as the process's(the process that called system call) kernel stack? Thanks & Regards

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