linux-kernel - RE: [PATCH v2 4/4] drivers: firmware: xilinx: Add debugfs interface

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Message-ID: <DM2PR0201MB0767AE5B7E37276806A3FED4B8E20@DM2PR0201MB0767.namprd02.prod.outlook.com>
Date:   Wed, 24 Jan 2018 23:33:50 +0000
From:   Jolly Shah <JOLLYS@...inx.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>,
        "sudeep.holla@....com" <sudeep.holla@....com>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Rajan Vaja <RAJANV@...inx.com>
Subject: RE: [PATCH v2 4/4] drivers: firmware: xilinx: Add debugfs interface

Thanks for review Greg,

> -----Original Message-----
> From: Greg KH [mailto:gregkh@...uxfoundation.org]
> Sent: Tuesday, January 23, 2018 12:41 AM
> To: Jolly Shah <JOLLYS@...inx.com>
> Cc: ard.biesheuvel@...aro.org; mingo@...nel.org; matt@...eblueprint.co.uk;
> sudeep.holla@....com; hkallweit1@...il.com; keescook@...omium.org;
> dmitry.torokhov@...il.com; michal.simek@...inx.com; robh+dt@...nel.org;
> mark.rutland@....com; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org; devicetree@...r.kernel.org; Rajan Vaja
> <RAJANV@...inx.com>; Jolly Shah <JOLLYS@...inx.com>
> Subject: Re: [PATCH v2 4/4] drivers: firmware: xilinx: Add debugfs interface
> 
> On Wed, Jan 17, 2018 at 12:20:34PM -0800, Jolly Shah wrote:
> > +/* Setup debugfs fops */
> > +static const struct file_operations fops_zynqmp_pm_dbgfs = {
> > +       .owner  =       THIS_MODULE,
> > +       .write  =       zynqmp_pm_debugfs_api_write,
> > +       .read   =       zynqmp_pm_debugfs_api_version_read,
> > +};
> > +
> > +/**
> > + * zynqmp_pm_api_debugfs_init - Initialize debugfs interface
> > + *
> > + * Return:      Returns 0 on success
> > + *             Corresponding error code otherwise
> > + */
> > +int zynqmp_pm_api_debugfs_init(void)
> > +{
> > +       int err;
> > +
> > +       /* Initialize debugfs interface */
> > +       zynqmp_pm_debugfs_dir = debugfs_create_dir(DRIVER_NAME, NULL);
> > +       if (!zynqmp_pm_debugfs_dir) {
> > +               pr_err("debugfs_create_dir failed\n");
> > +               return -ENODEV;
> > +       }
> 
> No, you should NEVER care if a debugfs call returned an error or not, no need to
> check it at all.  Your code path should not change based on the return value as
> no code should depened on the functionality of debugfs.
> 
> Any error returned by a debugfs call can be passed right back into it with no
> problems, so again, no need to check this.
> 

Fixed in v3 patch series. Not saving dentries anymore but added check to show warning message instead of error.

> > +
> > +       zynqmp_pm_debugfs_power =
> > +               debugfs_create_file("pm", 0220,
> > +                                   zynqmp_pm_debugfs_dir, NULL,
> > +                                   &fops_zynqmp_pm_dbgfs);
> > +       if (!zynqmp_pm_debugfs_power) {
> > +               pr_err("debugfs_create_file power failed\n");
> > +               err = -ENODEV;
> > +               goto err_dbgfs;
> > +       }
> > +
> > +       zynqmp_pm_debugfs_api_version =
> > +               debugfs_create_file("api_version", 0444,
> > +                                   zynqmp_pm_debugfs_dir, NULL,
> > +                                   &fops_zynqmp_pm_dbgfs);
> > +       if (!zynqmp_pm_debugfs_api_version) {
> > +               pr_err("debugfs_create_file api_version failed\n");
> > +               err = -ENODEV;
> > +               goto err_dbgfs;
> > +       }
> 
> Why do you save these dentries at all anyway?  You never do anything with
> them, just create the files and away you go, no need to worry about anything.
> 
> Remember, debugfs was created to be very simple to use, don't make it more
> complex than it has to be please.
> 
> thanks,
> 
> greg k-h

Fixed in v3 patch series.

Thanks,
Jolly Shah