Messages in this thread | | | Date | Tue, 11 Dec 2012 20:49:13 -0800 | From | Greg KH <> | Subject | Re: [PATCH 1/2] uio: add warning to documentation |
| |
On Wed, Dec 12, 2012 at 01:45:34AM +0100, Benedikt Spranger wrote: > On Tue, 11 Dec 2012 15:18:16 -0800 > Greg KH <gregkh@linuxfoundation.org> wrote: > > > > -<function>open()</function>, you will probably also want a custom > > > +<function>release()</function>, you will probably also want a > > > custom <function>release()</function> function. > > That sentance no longer makes sense. > DUH! will fix... > > > > +</para><para>CAVE: The release hook may be processed, even if a > > > mmap is aktive. > > Huh? > OK, think about a user of uio_pdrv_genirq and you did your > powermanagement well. The user open the UIO device, do a mmap() and > close the UIO device. Then he access the given pointer and wonders why > the system is stuck. It is a bad idea to disable clocks on release > while a mmap is active.
A UIO user is root and can do lots of bad things if they are foolish, are we supposed to enumerate all of them? :)
> > > +Disabling clocks or other powermanagement functionality may cause > > > a system +crash, hangup or other unwanted sideeffects. > > > +</para><para><emphasis>The mmap() function shall add an extra > > > reference to the file associated with the file descriptor fildes > > > which is not removed by a subsequent close() on that file > > > descriptor. This reference shall be removed when there are no more > > > mappings to the file.</emphasis></para><para> +<link > > > xlink:href="http://pubs.opengroup.org/onlinepubs/009695399/functions/mmap.html">IEEE > > > Std 1003.1, 2004 Edition, mmap()</link> > > > > It's not up to us to document the mmap system call here, you should > > know how to use it if you write a program with it, right? > Its not the user of mmap(), it is for the driver programmer. It is a > bad idea to do every kind of powermanagement function in the release > hook.
I agree, but how can a driver programmer use that information properly here?
greg k-h
| |