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Date:   Fri, 23 Jun 2023 13:14:42 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Kyle Tso <kyletso@google.com>
Cc:     heikki.krogerus@linux.intel.com, badhri@google.com,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] usb: typec: Use sysfs_emit_at when concatenating the
 string
Message-ID: <2023062327-bucked-backrest-c20d@gregkh>
References: <20230622150423.3726894-1-kyletso@google.com>
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 <2023062345-hassle-septic-b8b4@gregkh>
 <CAGZ6i=3BP4ssx31roJoGL_VT=o3mq9Lj_VfZ_HSywzPOEt3v7g@mail.gmail.com>
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On Fri, Jun 23, 2023 at 06:11:00PM +0800, Kyle Tso wrote:
> On Fri, Jun 23, 2023 at 6:06 PM Kyle Tso <kyletso@google.com> wrote:
> >
> > On Fri, Jun 23, 2023 at 3:51 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Thu, Jun 22, 2023 at 11:04:23PM +0800, Kyle Tso wrote:
> > > > The buffer address used in sysfs_emit should be aligned to PAGE_SIZE.
> > >
> > > Why?  Are you getting warnings about this?
> > >
> > > thanks,
> > >
> > > greg k-h
> >
> > Yes, here is the warning.
> >
> > [  223.243123] invalid sysfs_emit: buf:00000000eda2d647
> > [  223.243197] WARNING: CPU: 4 PID: 8860 at fs/sysfs/file.c:735
> > sysfs_emit+0xb0/0xc0
> > [  223.244335] CPU: 4 PID: 8860 Comm: cat
> > [  223.244363] pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
> > [  223.244378] pc : sysfs_emit+0xb0/0xc0
> > [  223.244394] lr : sysfs_emit+0xac/0xc0
> > ...
> > [  223.244560] Call trace:
> > [  223.244568] sysfs_emit+0xb0/0xc0
> > [  223.244582] select_usb_power_delivery_show+0x134/0x18c
> > [  223.244626] dev_attr_show+0x38/0x74
> > [  223.244654] sysfs_kf_seq_show+0xb4/0x130
> > [  223.244668] kernfs_seq_show+0x44/0x54
> > [  223.244683] seq_read_iter+0x158/0x4ec
> > [  223.244727] kernfs_fop_read_iter+0x68/0x1b0
> > [  223.244739] vfs_read+0x1d8/0x2b0
> > [  223.244775] ksys_read+0x78/0xe8
> >
> > The warning comes from
> > https://elixir.bootlin.com/linux/v6.3.9/source/fs/sysfs/file.c#L734
> >
> > if (WARN(!buf || offset_in_page(buf), "invalid sysfs_emit: buf:%p\n", buf))
> >         return 0;
> >
> > Kyle
> 
> BTW, to print the buf address, it should use %pK ...

Patches accepted :)