On Mon, Sep 14, 2009 at 1:57 PM, Pei Lin <[email protected]> wrote:
> SO u can use the first method,write files from the kernel space..... > See the hyperlink i give. > > Lin > > 2009/9/14 Leonidas . <[email protected]>: > > > > > > On Mon, Sep 14, 2009 at 1:22 PM, Leonidas . <[email protected]> > wrote: > >> > >> > >> Hi List > >> > >> I have written a kernel module which implements a char device. An > >> userspace app > >> is supposed to get data from my module and then dump it into a file for > >> further processing. > >> > >> The kind of data which kernel module is going to pass to userspace is > >> going to be a 4K buffer, > >> and the data traffic is not going to be really heavy, meaning may be a > 4K > >> buffer every 1 min or so. > >> I am not very sure though, but certainly not heavy traffic the way they > >> describe for network traffic etc. > >> > >> And this data needs to be logged to a file either from kernel or > userspace > >> and an userspace all will work > >> on that data. This data needs to be logged as soon as it arrives > meaning, > >> I might not be able to write it to > >> /proc since from module I can update /proc only when user actually > >> accesses it. This data needs to be > >> static in nature, meaning I get one error and I write it to a file > somehow > >> and user can see it anytime. > >> > >> I hope I have described the situation clearly. I have explored some > >> mechanism like ioctls, mmaping the > >> kernel buffer etc but all these would require the user module to poll or > >> notified somehow by kernel that > >> the data is available. I dont want the user module to poll. > >> > >> > >> -Leo. > >> > > > > When we do a printk it writes to kernel log buffer, correct? This is real > in > > time operation i.e. as soon as we do a > > printk the messages get logged. Now this log file can be accesses from > > /var/log/messages right? How is this done? > > > > I want to so something similar, so I can log my messages to a seprate > file > > which is going to stay around so user can > > see at across reboots as well. > > > > > > > > -Leo. > > > > > No, Greg KH mentions that is should not be done! And I have been reading that 'It is a bad..bad thing to access files from kernel space' since I started doing Linux stuff. _Leo.
