March 2017 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

[mm subsystem] A question about function page_table_range_init_count()
by Hao Lee March 21, 2017

March 21, 2017

Hi, all I encounter a problem when I read the source code of kernel 4.9.9. In arch/x86/mm/init_32.c, at line 125 [1], there is a function named page_table_range_init_count(...). I have analyzed some codes and find its two parameters are PKMAP_BASE and FIXADDR_START. Between Line 141 and Line 150, there is a for loop and I don't know what it means, especially Line 144-Line147. Could someone can give me some tips. Thanks a lot! Here is the code: [1] http://lxr.free-electrons.com/source/arch/x86/mm/init_32.c?v=4.9#L125 Hao Lee Thanks.

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Problem in First-Patch-Tutorial
by SIMRAN SINGHAL March 19, 2017

March 19, 2017

Reloading Modules make -j2 && sudo make modules_install sudo modprobe -r <module_name> sudo modprobe <module_name> In Reloading Modules I tried the first command it works fine for me. git/kernels/staging$ ls drivers/iio/dummy/*.ko drivers/iio/dummy/iio_dummy_evgen.ko drivers/iio/dummy/iio_dummy.ko Then I tried to run second-command git/kernels/staging$ sudo modprobe -r iio_dummy_evgen I got the following error:- modprobe: FATAL: Module iio_dummy_evgen not found. I am not getting what is wrong with this.

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Free Linux/Ubuntu VMs for Kernal Development?
by Balaji Barmavat March 16, 2017

March 16, 2017

Hello Team, Anybody's has any VM's links to download, for practice kernel programming? Thanks On Mon, Mar 13, 2017 at 7:45 PM, Tobin C. Harding <me(a)tobin.cc> wrote: > On Tue, Mar 14, 2017 at 10:08:51AM +0800, Greg KH wrote: > > On Tue, Mar 14, 2017 at 01:03:07PM +1100, Tobin C. Harding wrote: > > > On investigating call sites for 'return' in drivers/staging/ks7010/ > > > it can be seen that a number of functions us *custom* (positive) > > > integers to indicate error. Notwithstanding that they are positive, is > > > this ok for code in the kernel (i.e in order to get out of staging > > > does this need to be changed)? Functions in question have internal > linkage > > > and the error code is used for debug messages. > > > > > > Should these be > > > > > > A) left alone > > > B) made negative > > > C) changed to use standard error codes (i.e -ENOMEM etc) > > > > C) please > > Awesome. > > thanks, > Tobin. > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >

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monitor of SEGFAULT processes
by Lev Olshvang March 16, 2017

March 16, 2017

Thank you Greg and others advising on my first question. I am writing monitor sybsytem, abd here the question : Is it possible from kernel module or user space to monitor which processes were terminated abnormally ? I understand that trap gates are initialized to handle it , fill trap_info, then sig_info and send signal to faulting process. Is it correct to place a hook in these chain? probably in signal.c : next_signal()? If so what is the proper method, ex jprobe? ThanX

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pr_debug
by Tobin C. Harding March 16, 2017

March 16, 2017

why does calling pr_debug() with more than one argument cause a sparse warning? drivers/mmc/core/sdio_io.c:70:9: error: unknown field name in initializer sdio_io.c:70: pr_debug("SDIO: Enabling device %s...\n", sdio_func_id(func)); What can we do about this? thanks, Tobin.

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Rebase against linux-next tree?
by Perry Hooker March 16, 2017

March 16, 2017

I recently submitted a patch (attached below) that corrects a couple of 'sparse' warnings in drivers/staging/rtl8192u/r8192U_dm.c. I got this reply back from greg k-h: > This patch does not apply to my tree at all :( > Please rebase it against linux-next and try again. However, I thought I *was* working off linux-next. This is what I did: $ git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git $ git fetch linux-next $ git fetch --tags linux-next $ git remote update $ git checkout next-20170310 $ git apply 0001-staging-rtl8192u-use-__le16_to_cpu-instead-of-cast.patch ... and the patch applied ok. Just to be sure, I also did this: $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git $ git apply 0001-staging-rtl8192u-use-__le16_to_cpu-instead-of-cast.patch ... and the patch again applied OK. What am I doing wrong / where should I go for more info? Thanks, Perry --- drivers/staging/rtl8192u/r8192U_dm.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/staging/rtl8192u/r8192U_dm.c b/drivers/staging/rtl8192u/r8192U_dm.c index 9209aad..33d105d 100644 --- a/drivers/staging/rtl8192u/r8192U_dm.c +++ b/drivers/staging/rtl8192u/r8192U_dm.c @@ -2304,9 +2304,9 @@ static void dm_check_edca_turbo( /* For Each time updating EDCA parameter, reset EDCA turbo mode status. */ dm_init_edca_turbo(dev); u1bAIFS = qos_parameters->aifs[0] * ((mode&(IEEE_G|IEEE_N_24G)) ? 9 : 20) + aSifsTime; - u4bAcParam = (((u32)(qos_parameters->tx_op_limit[0])) << AC_PARAM_TXOP_LIMIT_OFFSET)| - (((u32)(qos_parameters->cw_max[0])) << AC_PARAM_ECW_MAX_OFFSET)| - (((u32)(qos_parameters->cw_min[0])) << AC_PARAM_ECW_MIN_OFFSET)| + u4bAcParam = (((u32)__le16_to_cpu(qos_parameters->tx_op_limit[0])) << AC_PARAM_TXOP_LIMIT_OFFSET) | + (((u32)__le16_to_cpu(qos_parameters->cw_max[0])) << AC_PARAM_ECW_MAX_OFFSET) | + (((u32)__le16_to_cpu(qos_parameters->cw_min[0])) << AC_PARAM_ECW_MIN_OFFSET) | ((u32)u1bAIFS << AC_PARAM_AIFS_OFFSET); /*write_nic_dword(dev, WDCAPARA_ADD[i], u4bAcParam);*/ write_nic_dword(dev, EDCAPARA_BE, u4bAcParam);

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driver dev mailing lists
by Tobin C. Harding March 15, 2017

March 15, 2017

What is the difference between these two mailing lists please? 1) devel(a)driverdev.osuosl.org 2) devel(a)linuxdriverproject.org drivers/staging/ks7010/TODO asks for patches to be sent to the second but scritps/get_maintainer.pl directs patches towards the first. thanks, Tobin.

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Merging device drivers to LK tree
by alexhoppus March 14, 2017

March 14, 2017

Hello! I have several questions regarding how device drivers are merged into linux-kernel. First of all, I have found some document regarding submitting drivers to LK, but it looks like pretty out-dated, https://kernelnewbies.org/UpstreamMerge/SubmittingDrivers is this info still relevant? Or there is a new one? Actually, I want to know more about the process. To start with this, I would like to ask an example question. Surfing through the kernel source I have found several ra-link usb wi-fi adapter drivers (rtl8188eu, rtl8192e, rtl8712 ...). Suppose one have datasheet that gives the possibility for writing a device driver for say rtlxxxxx based device. Can third-party person write & submit this driver to LK or this must be done explicitly by device vendor? What are the requirements from LK community side? Are there any license issues with this? (besides the author should publish code under GPL)

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coccinelle
by Tobin C. Harding March 14, 2017

March 14, 2017

Attempting to do transform using Coccinelle if (foo != 0) { ... -> if (foo) { ... Coccinelle script attempt does not work @@ expression x; @@ ( - x != 0 + x ) `spatch --parse-cocci script.cocci` appears to pass. A similar script worked correctly @@ expression x; @@ ( - x == 0 + !x ) I have read various papers and tutorials to no avail. I have tried various other versions also with no success. Any pointers most appreciated. thanks, Tobin.

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standard error codes
by Tobin C. Harding March 14, 2017

March 14, 2017

Driver code in staging/drivers/ks7010 uses the error code -E2BIG as the error returned if a string argument is larger than destination buffer. Would this not be better suited to the error code -EOVERFLOW? Does it matter? For reference; #define E2BIG 7 /* Argument list too long */ #define EOVERFLOW 75 /* Value too large for defined data type */ thanks, Tobin.

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