linux-kernel - Re: [char-misc-next 4/4 V2] mei: bus: enable non-blocking RX

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Date:   Wed, 30 Nov 2016 12:57:10 +0100
From:   'Greg Kroah-Hartman' <gregkh@...uxfoundation.org>
To:     "Winkler, Tomas" <tomas.winkler@...el.com>
Cc:     "Usyskin, Alexander" <alexander.usyskin@...el.com>,
        "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>
Subject: Re: [char-misc-next 4/4 V2] mei: bus: enable non-blocking RX

On Tue, Nov 29, 2016 at 08:09:38PM +0000, Winkler, Tomas wrote:
> 
> > On Mon, Nov 28, 2016 at 11:03:20PM +0000, Winkler, Tomas wrote:
> > > >
> > > >
> > > > >
> > > > > On Sat, Nov 19, 2016 at 02:16:11PM +0200, Tomas Winkler wrote:
> > > > > > From: Alexander Usyskin <alexander.usyskin@...el.com>
> > > > > >
> > > > > > Enable non-blocking receive for drivers on mei bus, this allows
> > > > > > checking for data availability by mei client drivers. This is
> > > > > > most effective for fixed address clients, that lacks flow control.
> > > > > >
> > > > > > This function adds new API function mei_cldev_recv_nonblock(),
> > > > > > it retuns -EGAIN if function will block.
> > > > > >
> > > > > > Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
> > > > > > Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
> > > > > > ---
> > > > > > V2: use _nonblock() function suffix instead of NONBLOCK flag
> > > > > >
> > > > > >  drivers/misc/mei/bus-fixup.c |  4 ++--
> > > > > >  drivers/misc/mei/bus.c       | 31 +++++++++++++++++++++++++++++--
> > > > > >  drivers/misc/mei/mei_dev.h   |  7 ++++++-
> > > > > >  include/linux/mei_cl_bus.h   |  6 ++++--
> > > > > >  4 files changed, 41 insertions(+), 7 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/misc/mei/bus-fixup.c
> > > > > > b/drivers/misc/mei/bus-fixup.c index 7f2cef9011ae..18e05ca7584f
> > > > > > 100644
> > > > > > --- a/drivers/misc/mei/bus-fixup.c
> > > > > > +++ b/drivers/misc/mei/bus-fixup.c
> > > > > > @@ -141,7 +141,7 @@ static int mei_osver(struct mei_cl_device
> > *cldev)
> > > > > >  	if (ret < 0)
> > > > > >  		return ret;
> > > > > >
> > > > > > -	ret = __mei_cl_recv(cldev->cl, buf, length);
> > > > > > +	ret = __mei_cl_recv(cldev->cl, buf, length, 0);
> > > > >
> > > > > What is 0 here?  Again, mode...
> > > >
> > > > Yes,  it means no change in behavior,  but this is an internal function.
> > 
> > So, it makes no sense, are you not going to have to read this code again in 10
> > years?  New developers?  Make the code make sense please.
> 
> 
> Sorry Greg, the code does make sense to me, the whole kernel passes nonblock around as flag starting from the syscall (O_NONBLOCK)
>  it doesn't make sense to write two functions that differ in one 'if' statement.
> I understand that you  are in some crusade against flags, but you are  not proposing a concrete solution and I don't have one either.
> I can solve it in the external wrapper, but internally it's just a same function.

What is wrong with your email client that it doesn't wrap things
properly?

Anyway, I don't remember anymore, please resend and I will review it
then.

greg k-h