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

[Gupta, Nipun]

[AMD Official Use Only - General]



> -----Original Message-----
> From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> Sent: Wednesday, August 3, 2022 6:02 PM
> To: Gupta, Nipun <Nipun.Gupta@xxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> rafael@xxxxxxxxxx; maz@xxxxxxxxxx; tglx@xxxxxxxxxxxxx; okaya@xxxxxxxxxx;
> Anand, Harpreet <harpreet.anand@xxxxxxx>; Simek, Michal
> <michal.simek@xxxxxxx>; Agarwal, Nikhil <nikhil.agarwal@xxxxxxx>
> 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@xxxxxxx>
> > ---
> >  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