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

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Date:   Wed, 18 Nov 2020 16:56:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Prashant Malani <pmalani@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [RFC PATCH 3/3] usb: typec: Expose Product Type VDOs via sysfs

On Wed, Nov 18, 2020 at 06:00:59PM +0300, Heikki Krogerus wrote:
> From: Prashant Malani <pmalani@...omium.org>
> 
> 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@...omium.org>
> [ heikki: Only one instead of three attribute files ]
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>'
> ---
>  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.

thanks,

greg k-h