linux-kernel - Re: [PATCH 1/3] uio: Allow handling of non page-aligned memory regions

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Message-ID: <20170316140739.GC30080@kroah.com>
Date:   Thu, 16 Mar 2017 23:07:39 +0900
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Michal Sojka <sojkam1@....cvut.cz>
Cc:     linux-kernel@...r.kernel.org, lisovy@...il.com
Subject: Re: [PATCH 1/3] uio: Allow handling of non page-aligned memory
 regions

On Thu, Mar 16, 2017 at 02:33:25PM +0100, Michal Sojka wrote:
> On Thu, Mar 16 2017, Greg KH wrote:
> > On Thu, Mar 16, 2017 at 01:45:50PM +0100, Michal Sojka wrote:
> >> On Thu, Mar 16 2017, Greg KH wrote:
> >> > On Tue, Mar 07, 2017 at 03:09:46PM +0100, Michal Sojka wrote:
> >> >> Since commit b65502879556 ("uio: we cannot mmap unaligned page
> >> >> contents") addresses and sizes of UIO memory regions must be
> >> >> page-aligned. If the address in the BAR register is not page-aligned,
> >> >> the mentioned commit forces the UIO driver to round the address down
> >> >> to the page size. Then, there is no easy way for user-space to learn
> >> >> the offset of the actual memory region within the page, because the
> >> >> offset seen in the sysfs is calculated from the rounded address and
> >> >> thus it is always zero.
> >> >> 
> >> >> Fix that problem by including the offset in struct uio_mem. UIO
> >> >> drivers can set this field and its value is reported via sysfs.
> >> >
> >> > It is, where?
> >> 
> >> /sys/class/uio/uio0/maps/map0/offset
> >
> > Did you change the Documentation/ABI entry for it?
> 
> No, because it seems that UIO is not documented there.

Wow, it really isn't, that sucks, I messed up :(

But, the uio-howto.rst file should probably be updated, right?

thanks,

greg k-h