Re: [RFC PATCH 3/3] usb: typec: Expose Product Type VDOs via sysfs

From: Heikki Krogerus
Date: Thu Nov 19 2020 - 07:11:14 EST


On Wed, Nov 18, 2020 at 04:56:57PM +0100, Greg Kroah-Hartman wrote:
> On Wed, Nov 18, 2020 at 06:00:59PM +0300, Heikki Krogerus wrote:
> > From: Prashant Malani <pmalani@xxxxxxxxxxxx>
> >
> > Interim. ABI doc missing.
> >
> > A PD-capable device can return up to 3 Product Type VDOs as part of its
> > DiscoverIdentity Response (USB PD Spec, Rev 3.0, Version 2.0, Section
> > 6.4.4.3.1). Add sysfs attribute to expose these to userspace.
> >
> > Signed-off-by: Prashant Malani <pmalani@xxxxxxxxxxxx>
> > [ heikki: Only one instead of three attribute files ]
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>'
> > ---
> > drivers/usb/typec/class.c | 41 +++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 41 insertions(+)
> >
> > diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> > index 303f054181ff7..5e135678f5952 100644
> > --- a/drivers/usb/typec/class.c
> > +++ b/drivers/usb/typec/class.c
> > @@ -165,15 +165,55 @@ static ssize_t product_show(struct device *dev, struct device_attribute *attr,
> > }
> > static DEVICE_ATTR_RO(product);
> >
> > +static ssize_t
> > +product_type_vdo_show(struct device *dev, struct device_attribute *attr, char *buf)
> > +{
> > + struct usb_pd_identity *id = get_pd_identity(dev);
> > + size_t len = 0;
> > + int i;
> > +
> > + for (i = 0; i < 3; i++) {
> > + if (!id->vdo[i])
> > + break;
> > + len += sysfs_emit(buf, "%08x ", id->vdo[i]);
> > + }
> > +
> > + buf[len - 1] = '\n';
> > +
> > + return len;
> > +}
>
> I don't understand what you are trying to print out here, documentation
> would be helpful :)
>
> > +static struct device_attribute dev_attr_product_type_vdo = {
> > + .attr = {
> > + .name = "product_type",
> > + .mode = 0444,
> > + },
> > + .show = product_type_vdo_show,
> > +};
>
> DEVICE_ATTR_RO(product_type_vdo)?
>
> Why are you calling it "product_type" and not with the "vdo"?
>
> And you have to name it this, there's always __ATTR_RO(), never put a
> mode in "raw" numbers for a sysfs file if at all possible.

Sorry Greg. This is still work-in-progress.

I didn't use the _vdo ending in the file name because the other files
exposing the other parts (VDOs) of the response to the discover
identity don't have it either.


thanks,

--
heikki