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From:   Alan Tull <atull@kernel.org>
Date:   Wed, 3 Apr 2019 13:37:51 -0500
Message-ID: <CANk1AXSJ31Q7X3J6NOsqVkQoJkjJz=xka0XiWvuYC36s1HiBuA@mail.gmail.com>
Subject: Re: [PATCHv1] fpga: mgr: add FPGA configuration log
To:     Moritz Fischer <mdf@kernel.org>
Cc:     Richard Gong <richard.gong@linux.intel.com>,
        linux-fpga@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Richard Gong <richard.gong@intel.com>
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On Wed, Apr 3, 2019 at 1:05 PM Alan Tull <atull@kernel.org> wrote:
>
> On Wed, Apr 3, 2019 at 11:47 AM Moritz Fischer <mdf@kernel.org> wrote:
> >
> > Hi Richard,
> >
> > On Wed, Apr 03, 2019 at 11:43:26AM -0500, Richard Gong wrote:
> > > Hi Moritz,
> > >
> > >
> > > On 4/3/19 9:20 AM, Moritz Fischer wrote:
> > > > Hi Richard,
> > > >
> > > > On Tue, Apr 02, 2019 at 05:25:43PM -0500, richard.gong@linux.intel.com wrote:
> > > > > From: Richard Gong <richard.gong@intel.com>
> > > > >
> > > > > Add a log for user to know FPGA configuration is successful
> > > > >
> > > > > Signed-off-by: Richard Gong <richard.gong@intel.com>
> > > > > ---
> > > > >   drivers/fpga/fpga-mgr.c | 1 +
> > > > >   1 file changed, 1 insertion(+)
> > > > >
> > > > > diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
> > > > > index c386681..559e046 100644
> > > > > --- a/drivers/fpga/fpga-mgr.c
> > > > > +++ b/drivers/fpga/fpga-mgr.c
> > > > > @@ -151,6 +151,7 @@ static int fpga_mgr_write_complete(struct fpga_manager *mgr,
> > > > >           }
> > > > >           mgr->state = FPGA_MGR_STATE_OPERATING;
> > > > > + dev_info(&mgr->dev, "Successfully programming FPGA\n");
> > > >
> > > > That info is available in FPGA manager's sysfs status entry, if at all
> > > > I'd make this a dev_dbg().
> > > >
> > > >  From my end I don't see how we need this really.
> > >
> > > We got requests from the field and they want to see a log to get know if
> > > FPGA configuration is successfully completed. They don't want use any
> > > additional command to get status.
> > >
> > > This log is useful for the user who performs FPGA configuration.
> > >
> > > I think we need use dev_info, since dev_dbg is not enabled by fault for most
> > > build.
> >
> > Well basically it boils down to:
> >
> > $ dmesg | grep "Sucessfully"
> >
> > vs
> >
> > $ cat /sys/class/fpga.../status
>
> it's state, not status for most fpga manager drivers.  It should
> return 'operating' if everything went well.
>
> It seems like there's a possible scenario where the FPGA starts up
> with the FPGA in 'operating' mode and the user messes up early enough
> that the state doesn't change.
>
> >
> > Personally not in favor of extra messages, but if we do it we should
> > change the message to "Sucessfully programmed FPGA".
> >
> > I think making it a dbg message is a good trade-off ...

dbg vs info... On the one hand, it is a usually a message the
developer wants to see so the developer would turn on debug messages.
But then again FPGA programming doesn't happen that often and it is a
kind of significant event since it is your hardware changing i.e. it
won't add a lot messages, but it is sort of an important one if it
happens.   If the system crashes after a FPGA reprogramming event, it
would be good to have this in the log by default.  I don't want to
argue too powerfully for adding extra messages though.  Is this a case
where info is worth it since fpga programming is significant?

> >
> > Moritz