linux-kernel - RE: [PATCH v3 2/4] bus: fsl-mc: add fsl-mc userspace support

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Message-ID: <VI1PR0402MB2800CF10719D11DD21F47356E0D90@VI1PR0402MB2800.eurprd04.prod.outlook.com>
Date:   Tue, 20 Nov 2018 16:51:07 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     Laurentiu Tudor <laurentiu.tudor@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev-owner@...r.kernel.org" <netdev-owner@...r.kernel.org>,
        Ioana Ciocoi Radulescu <ruxandra.radulescu@....com>,
        Horia Geanta <horia.geanta@....com>,
        Leo Li <leoyang.li@....com>
Subject: RE: [PATCH v3 2/4] bus: fsl-mc: add fsl-mc userspace support

> On Tue, Nov 20, 2018 at 03:39:45PM +0000, Ioana Ciornei wrote:
> > +
> > +			error = fsl_mc_uapi_create_device_file(mc_bus);
> > +			if (error < 0) {
> > +				error = -EPROBE_DEFER;
> > +				goto error_cleanup_msi_domain;
> > +			}
> 
> What error could occur here that would be somehow fixed if you defer and try
> this all again?  Shouldn't you just return the error given (as something really went
> wrong here, it's not a "something else needs to start up first issue), and abort?
> 

It's really a "something else needs to start up first" type of issue. The fsl_mc_uapi_create_device_file fails only if the misc_register fails and this could really happen when the misc char driver is not yet initialized.

Initially, I have used the register_chrdev API and you suggested to use a misc device and just defer probe if it's not yet initialized.

Ioana C


> thanks,
> 
> greg k-h