2009/9/18 Leonidas . <leonidas137@xxxxxxxxx>: > > > On Fri, Sep 18, 2009 at 7:32 AM, Pei Lin <telent997@xxxxxxxxx> wrote: >> >> 2009/9/17 Leonidas . <leonidas137@xxxxxxxxx>: >> > >> > >> > Hi list, >> > >> > I know that introducing/using new ioctls is frawned upon by the >> > community. >> > They might still be needed for controlling various hw parameters, Just >> > wanted >> > to understand the data transfer side of ioctls with a use case. >> > >> > E.g. My kernel module needs to pass a buffer of 1-2Mb to userspace >> > whenever user requests. The buffer will contain different kind of data >> > depending >> > on different commands i.e. assume that I maintain 3 types of buffers in >> > my >> > module. >> > >> > Now, with ioctls it is much easiler to get the buffer to userspace >> > simply by >> > issusing >> > different commands. But if I have to achive the same functionality using >> > read() call >> > how would I do it? Meaning ioctl kind of multiplexes the things which >> > might >> > be >> > needed in some cases. How would I do this kind of stuff with read()? By >> > having 3 >> > different minor devices and issuing read() on 3 devices for getting 3 >> > buffers? >> > >> hi, leo >> just implement your ioctl function, create the command, and decode >> command,deliver your command and buffer point (user) into your >> module,then use copy_from_user /copy_to_user deliver your buffer from >> user to kernel or vice versa. >> >> > I am not looking for anyother mechanism of trasnfering data to userspace >> > as >> > of now >> > since this data would be really sporadic. I have to choose between ioctl >> > and >> > read. >> > >> > -Leo. >> > >> >> >> >> -- >> Best Regards >> Lin > > Peter, > > No it is going to be a simple char device. Actually a pseudo device since it > is not going > to be associated with any hw buffers. The buffers which I need to transfer > are some > bookkeeping buffers I would maintain in my module. So the usd stuff which > you mention > might not be appropriate. > > Lin, > > I think you are talking about ioctl on a single minor number device, my > concern is more > about choice here. Meaning whether using ioctls with different commands on a > single dev > node be preferable to issuing reads on 3 different minor number device > nodes. i think u just need read the codes in the kernel driver char/tty* especially tty_ioctl.c and Document devices.txt and files in ioctl folder. > > > -Leo. > > -- Best Regards Lin -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
