January 2017 - kernelnewbies@kernelnewbies.org

How to build an external module in a specified directory?
by Shiyao Ma Jan. 3, 2017

Jan. 3, 2017

Hi, When building an external module, for example, given this command, all: $(MAKE) -C $(KDIR) M=$$PWD It will build the ko file in the $PWD. How to specify a location for the .ko files? Regards.

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Doubt in Eudyptula Challenge
by deeksha varshney Jan. 2, 2017

Jan. 2, 2017

Hello sir, I am not able to understand what to write in the subject line along with the ID while submitting the task 01.Please help I am getting the following reply from Little I can not understand your Subject: line, please read the introductory email and fix the subject to match exactly as it says in order for me to be able to parse it properly. Deeksha

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[MMC_SPI] CMD 18 error -84 transferring data
by Amit Mahadik Jan. 2, 2017

Jan. 2, 2017

Hello, I am using ARM (CortexA9)development board which has SPI controller running at 5MHz. I want to interface MMC card on SPI bus. I have made changes to my board.c file to include the mmc_spi driver and mentioned the Chip select, mode (MODE 0) and frequency of operation (started with 40kHz tried with 25MHz as well). The initial card detection goes well. However, there are CRC errors when the block layer tries to read the partition table. This issue is reproducible. I have attached log for reference. The card gets detected on Linux/Windows PC. The card is formatted with DOS partition (vfat single partition). Linux kernel version Used : 4.4.16 Please help me regarding this issue. Regards, Amit.

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Question about object-based reverse mapping
by Hao Lee Jan. 1, 2017

Jan. 1, 2017

Hi, all I'm currently reading "Understanding the Linux Kernel (3rd)" and I have a question about "object-based reverse mapping". This is the Figure 17-1 on page 683 : http://imgur.com/R0OtIJh As this figure shows, many vm_area_struct are in the anon_vma’s list and they share some page frames. The index field in page struct represents the offset of virtual address within the virtual memory area. What I want to know is what would happen when a page frame is shared by several vm_area_struct. If two virtual memory areas share the same page frame, it seems that page->index would be overridden because there are two vma and the variable index would be assigned two times. How the linux kernel prevent it happening. Thanks. Hao Lee

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