linux-kernel - Re: [PATCH] ipmi:ssif: Improve detecting during probing

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Message-ID: <20240826113150.42lyq6nmkyn53cv6@localhost.localdomain>
Date: Mon, 26 Aug 2024 14:31:50 +0300
From: "Ivan T. Ivanov" <iivanov@...e.de>
To: Corey Minyard <corey@...yard.net>
Cc: openipmi-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ipmi:ssif: Improve detecting during probing

Hi,

On 08-22 09:40, Corey Minyard wrote:
> > > +++ b/drivers/char/ipmi/ipmi_ssif.c
> > > @@ -1368,8 +1368,20 @@ static int ssif_detect(struct i2c_client *client, struct i2c_board_info *info)
> > >  	rv = do_cmd(client, 2, msg, &len, resp);
> > >  	if (rv)
> > >  		rv = -ENODEV;
> > 
> > What is my worry is that in case of SMBus errors, device is there but
> > for some reason it got stuck/crashed or whatever, so will get out of
> > detect function from here and with ENODEV return code probe function
> > will be called for no reason.
> 
> That's not how the i2c code works.  See my next comment.
> 
> > 
> > > -	else
> > > +	else {
> > > +	    if (len < 3) {
> > > +		rv = -ENODEV;
> > 
> > No point to call probe(), right?
> 
> Originally (before I add the call from ssif_probe()), this is not involved in
> the probe() call.  Instead, the detect function is involved in calling a
> table of addresses in driver->address_list.  So in this case this
> function is never called at all from the i2c code, since there is no
> address list.

I see, thank you for explanation.

> > >  
> > > +	/*
> > > +	 * Send a get device id command and validate its response to
> > > +	 * make sure a valid BMC is there.
> > > +	 */
> > > +	rv = ssif_detect(client, NULL);
> > > +	if (rv) {
> > > +		dev_err(&client->dev, "Not present\n");
> > > +		goto out;
> > > +	}
> > > +
> > 
> > The point is that even after this point IPMI device can start failing
> > to properly communicate with the OS, real SMBus errors, like EREMOTEIO
> > in my case, but unfortunately code bellow do not handle this very well,
> > I think.
> 
> It is possible that the BMC gets rebooted or something between the call
> to ssif_detect() and the code below, but the probability is really low.
> If it answers a detect, the rest of the things should work.
> 

I have my daubs, but patch proposed will fix the issue that I see.

Thank you,
Ivan