Messages in this thread | | | Date | Wed, 12 Dec 2012 01:45:34 +0100 | From | Benedikt Spranger <> | Subject | Re: [PATCH 1/2] uio: add warning to documentation |
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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.
> > +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.
Regards Bene
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