linux-kernel - RE: [RFC PATCH 2/2] driver core: add compatible string in sysfs for platform devices

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Message-ID: <DM6PR12MB30827E57AA6000BDC5AE6FEDE89C9@DM6PR12MB3082.namprd12.prod.outlook.com>
Date:   Wed, 3 Aug 2022 12:46:32 +0000
From:   "Gupta, Nipun" <Nipun.Gupta@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "maz@...nel.org" <maz@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "okaya@...nel.org" <okaya@...nel.org>,
        "Anand, Harpreet" <harpreet.anand@....com>,
        "Simek, Michal" <michal.simek@....com>,
        "Agarwal, Nikhil" <nikhil.agarwal@....com>
Subject: RE: [RFC PATCH 2/2] driver core: add compatible string in sysfs for
 platform devices

[AMD Official Use Only - General]



> -----Original Message-----
> From: Greg KH <gregkh@...uxfoundation.org>
> Sent: Wednesday, August 3, 2022 6:02 PM
> To: Gupta, Nipun <Nipun.Gupta@....com>
> Cc: linux-kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> rafael@...nel.org; maz@...nel.org; tglx@...utronix.de; okaya@...nel.org;
> Anand, Harpreet <harpreet.anand@....com>; Simek, Michal
> <michal.simek@....com>; Agarwal, Nikhil <nikhil.agarwal@....com>
> Subject: Re: [RFC PATCH 2/2] driver core: add compatible string in sysfs for
> platform devices
> 
> [CAUTION: External Email]
> 
> On Wed, Aug 03, 2022 at 05:56:55PM +0530, Nipun Gupta wrote:
> > For devices registered dynamically using platform_device_register
> > API, this patch exposes the sysfs entry for the compatible string.
> >
> > Signed-off-by: Nipun Gupta <nipun.gupta@....com>
> > ---
> >  drivers/base/platform.c | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> >
> > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> > index 51bb2289865c..89949f88a0a1 100644
> > --- a/drivers/base/platform.c
> > +++ b/drivers/base/platform.c
> > @@ -1289,10 +1289,25 @@ static ssize_t driver_override_store(struct device
> *dev,
> >  }
> >  static DEVICE_ATTR_RW(driver_override);
> >
> > +static ssize_t compatible_show(struct device *dev, struct device_attribute
> *attr,
> > +                           char *buf)
> > +{
> > +     const char *compat;
> > +     int ret;
> > +
> > +     ret = device_property_read_string(dev, "compatible", &compat);
> > +     if (ret != 0)
> > +             return 0;
> > +
> > +     return sysfs_emit(buf, "%s", compat);
> > +}
> > +static DEVICE_ATTR_RO(compatible);
> 
> You forgot the Documentation/ABI/ update :(

Thanks for pointing. Will be adding the new sysfs entry as part
of the documentation.

> 
> Also, what happens if there is no such string to read?  Why are you
> returning 0?  You should not create the attribute at all then, right?

Will be updating platform_dev_attrs_visible() API to have it visible
depending on if the attribute is available. Yes, then we may not need
this check here and would be part of the platform_dev_attrs_visible() API.

Thanks,
Nipun

> 
> thanks,
> 
> greg k-h