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Date: Mon, 6 Feb 2012 16:15:58 -0800 From: Greg KH <greg@...ah.com> To: Adam Jackson <ajax@...hat.com> Cc: linux-kernel@...r.kernel.org, arnd@...db.de Subject: Re: [PATCH] char/mem: Make /dev/port less obviously broken (v0) On Mon, Feb 06, 2012 at 06:02:02PM -0500, Adam Jackson wrote: > Did you know /dev/port turns all reads and writes into a stream of inb > and outb? Turns out hardware really does care about I/O cycle size > though, and if you're trying to do an outl four outb's is very much not > the same thing. > > However, someone somewhere probably built some code and hardware that > relies on that behaviour. Plus, userspace needs to be able to tell > whether the kernel will do the right thing, and fall back to raw port > access if not. So add an ioctl to request new 'strict' semantics, which > allows only exactly 1/2/4 byte cycles and translates them into the > corresponding I/O cycle size. This matches the behaviour of sysfs's > resourceN files for I/O BARs. Who would use this new ioctl? And if it's been working ok until now, why is it needed? If you want something "new" like this, why not just create /dev/ioport or something like that to always use the proper alignment and not need an ioctl at all? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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