Messages in this thread |  | | | Date | Mon, 24 Nov 2008 20:11:16 -0800 | | From | Greg KH <> | | Subject | Re: [PATCH RFC] UIO: Pass information about ioports to userspace |
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On Mon, Nov 24, 2008 at 11:19:15AM +0100, Hans J. Koch wrote: > On Sun, Nov 23, 2008 at 05:40:54PM -0800, Greg KH wrote: > > On Sun, Nov 23, 2008 at 01:14:20PM +0100, Hans J. Koch wrote: > > > Devices sometimes have memory where all or parts of it can not be mapped to > > > userspace. But it might still be possible to access this memory from > > > userspace by other means. An example are PCI cards that advertise not only > > > mappable memory but also ioport ranges. On x86 architectures, these can be > > > accessed with ioperm, iopl, inb, outb, and friends. Mike Frysinger (CCed) > > > reported a similar problem on Blackfin arch where it doesn't seem to be easy > > > to mmap non-cached memory but it can still be accessed from userspace. > > > > > > This patch allows kernel drivers to pass information about such ports to > > > userspace. Similar to the existing mem[] array, it adds a port[] array to > > > struct uio_info. Each port range is described by start, size, and porttype. > > > > > > If a driver fills in at least one such port range, the UIO core will simply > > > pass this information to userspace by creating a new directory "portio" > > > underneath /sys/class/uio/uioN/. Similar to the "mem" directory, it will > > > contain a subdirectory (portX) for each port range given. > > > > This is good, but it would really be nice to provide a way for userspace > > to access individual ports without having to have access to all ports in > > the system. Lots of times we don't want to give root privileges to some > > programs that only need to read and write simple data to a single > > device. > > Yes, of course, that'd be nice. But it's very much arch dependent. For > example, these x86 ioports need special handling on x86, but you can simply > mmap them on powerpc. Port-like memory ranges on other archs might require > something completely different. > Yes, some generic port access layer would really be good, but I'm not sure > if the UIO core is the right place to implement it. Do you already have a > solution in mind?
No I don't, sorry, it's just come up a few times recently and I was hoping that you would have something :)
> Maybe we can look at that in a second step. ATM I just want to avoid these > situations where userspace needs ugly tricks to find out which ioports > belong to a certain card.
Agreed, I'm not saying that this patch is not ok at all, sorry if you misinterpreted it that way. I have no objection to this patch, as long as it includes the needed documentation.
thanks,
greg k-h
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