tags:

views:

33

answers:

0
Q: 

implement mmap with multiple pages in device driver

I have a device driver that uses buffers in RAM that I want the user to be able to map to user space. I have read http://lwn.net/images/pdf/LDD3/ch15.pdf which talks about using nopages, but the example there only uses single pages and says you can adjust usage counts to make it work for multiple pages. I don't understand how that works. It uses get_free_page with an order of 0 (so 1 free page) to allocate its buffers, but my buffer is two pages long.

What does the usage count have to do with anything? From what I understand, only the first page is counted.

related questions

mmap and access to GPIO config registers in an ARM processor
wx.TextCtrl.LoadFile()
mmap(2) vs mmap(3)
What is the fastest way to read 10 GB file from the disk?
mmap to overlay VME bus into user space memory over a PCI?
mmaping large files(for persistent large arrays)
Linux mmap() error
How to mmap the stack for the clone() system call on linux?
Linux/perl mmap performance
mmap big endian vs. little endian
Shmem vs tmpfs vs mmap
will mmap use user cpu instead of whole sys cpu? (solaris)
Memory usage of FileChannel#map
Will mmap use continuous memory? (on solaris)
mmap() internals
Linux MMAP internals
Using mmap over a file
How big can a memory-mapped file be?
Examining mmaped addresses using GDB
Passing a pointer to process spawned with exec()
mmap protection flag effect to sharing between processes
How to share APC cache between several PHP processes when running under FastCGI?
caching a tar inside jvm for faster file I/O?
When should I use mmap for file access?
mmap() vs. reading blocks